<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.4 20241031//EN" "JATS-journalpublishing1-4.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="1.4" xml:lang="en">
  <front>
    <journal-meta>
      <journal-id journal-id-type="publisher-id">jhepgc</journal-id>
      <journal-title-group>
        <journal-title>Journal of High Energy Physics, Gravitation and Cosmology</journal-title>
      </journal-title-group>
      <issn pub-type="epub">2380-4335</issn>
      <issn pub-type="ppub">2380-4327</issn>
      <publisher>
        <publisher-name>Scientific Research Publishing</publisher-name>
      </publisher>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.4236/jhepgc.2026.123073</article-id>
      <article-id pub-id-type="publisher-id">jhepgc-152299</article-id>
      <article-categories>
        <subj-group>
          <subject>Article</subject>
        </subj-group>
        <subj-group>
          <subject>Physics</subject>
          <subject>Mathematics</subject>
        </subj-group>
      </article-categories>
      <title-group>
        <article-title>Gravitational Wave Radiation from the Antimatter Universe</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <contrib-id contrib-id-type="orcid">0000-0001-8549-1192</contrib-id>
          <name name-style="western">
            <surname>El-Sherbini</surname>
            <given-names>Tharwat M.</given-names>
          </name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
      </contrib-group>
      <aff id="aff1"><label>1</label> Physics Department, Faculty of Science, Cairo University, Giza, Egypt </aff>
      <author-notes>
        <fn fn-type="conflict" id="fn-conflict">
          <p>The author declares no conflicts of interest regarding the publication of this paper.</p>
        </fn>
      </author-notes>
      <pub-date pub-type="epub">
        <day>03</day>
        <month>06</month>
        <year>2026</year>
      </pub-date>
      <pub-date pub-type="collection">
        <month>06</month>
        <year>2026</year>
      </pub-date>
      <volume>12</volume>
      <issue>03</issue>
      <fpage>1436</fpage>
      <lpage>1446</lpage>
      <history>
        <date date-type="received">
          <day>09</day>
          <month>01</month>
          <year>2026</year>
        </date>
        <date date-type="accepted">
          <day>27</day>
          <month>06</month>
          <year>2026</year>
        </date>
        <date date-type="published">
          <day>30</day>
          <month>06</month>
          <year>2026</year>
        </date>
      </history>
      <permissions>
        <copyright-statement>© 2026 by the authors and Scientific Research Publishing Inc.</copyright-statement>
        <copyright-year>2026</copyright-year>
        <license license-type="open-access">
          <license-p> This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link> ). </license-p>
        </license>
      </permissions>
      <self-uri content-type="doi" xlink:href="https://doi.org/10.4236/jhepgc.2026.123073">https://doi.org/10.4236/jhepgc.2026.123073</self-uri>
      <abstract>
        <p>Since the advent of gravitational wave astronomy in the second decade of this century—due to the observation of gravitational waves by LIGO detectors in 2015, there are active efforts by many astrophysicists to propose different theoretical models to explain and test this phenomenon. In this article, we study gravitational wave radiation from the previously proposed anti-matter universe. The emitted continuous-gravitational wave radiation from the compact core of the anti-universe and its relativistic rotating outer plasma layer, are considered as perturbative waves in toroidal r-mode oscillations driven by rotation and Coriolis forces. The most prominent toroidal-bulk mode for gravitational wave emission is the <inline-formula><mml:math></mml:math></inline-formula></p>
        <p>l=2</p>
        <p>, <inline-formula><mml:math></mml:math></inline-formula></p>
        <p>m=2</p>
        <p>, and its range of frequencies is approximately ≈ 135 - 632 Hz. This mode is likely detectable by LIGO or VIRGO detectors where their sensitivities are high enough in this range of frequencies. The power radiated from this mode adapted for rapidly rotating compact object (anti-universe) with compactness parameter <italic>C</italic> ≈ 0.49, is evaluated to be approximately ≈ 1.4 × 10<sup>39</sup> W. Gravitational wave-strain amplitudes are calculated using the quadrupole formula adjusted for r-modes, estimating the distance between the antimatter universe and the observer to be of the order of magnitude of the radius of our observable universe which is approximately 46.5 billion lightyears (4.4 × 10<sup>36</sup> m), about 0.24 × 10<sup>−</sup><sup>29</sup>, after incorporating GR frame dragging (Lense Thirring effect) correction. This value is too weak for any currently operating gravitational wave detector to observe. However, the high sensitivity cryogenic LIGO/VIRGO detectors or the future planned laser interferometer space antenna (LISA), could plausibly detect the continuous emitted gravitational waves from the antimatter universe.</p>
      </abstract>
      <kwd-group kwd-group-type="author-generated" xml:lang="en">
        <kwd>Astrophysical Cosmology</kwd>
        <kwd>Antimatter Universe</kwd>
        <kwd>Gravitational Waves</kwd>
        <kwd>Dark Energy</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec1">
      <title>1. Introduction</title>
      <p>The study of antimatter in the universe offers new perspectives on the physical nature of our universe [<xref ref-type="bibr" rid="B1">1</xref>][<xref ref-type="bibr" rid="B2">2</xref>].</p>
      <p>In a previous publication [<xref ref-type="bibr" rid="B3">3</xref>], we studied the electromagnetic radiation emitted from the antimatter universe that was formed as a result of the ejection of primordial anti-S particles during the <bold>Big Bang</bold> [<xref ref-type="bibr" rid="B4">4</xref>].</p>
      <p>Following the anti-universe evolution processes, a dense anti-hydrogen gas collapsed under its own gravity and accreted with time forming a compact object (the core of the anti-universe). However, the high surface temperature, pressure and collisions resulted in the ionization of the anti-hydrogen atoms on the surface forming a thin plasma layer of free negatively charged heavy anti-protons and positively charged light positrons. The strong centrifugal force acting on the charged particles leads, together with their ultra-fast rotation, to the emission of a synchrotron type—electromagnetic radiation mainly from the lighter positron layer [<xref ref-type="bibr" rid="B3">3</xref>]. </p>
      <p>In this article, the author investigates the possibility of gravitational wave (GW) emission by the anti-matter universe. The article will be structured as follows: in Section 2, the spectrum of toroidal oscillations is discussed; then in Section 3, the power of gravitational wave is calculated, and the gravitational strain is evaluated; finally the conclusions are given in Section 4. </p>
      <p>The author has previously proposed [<xref ref-type="bibr" rid="B3">3</xref>], that the radius of the core of the anti-universe, in the early phase, is about 150 Km. However, in the present article, which is a continuation to the previous one, he found that the proposed value is smaller than the corresponding Schwarzschild radius (about 295 Km), suggesting that the compact object (the anti-universe) could be a black hole that might not support toroidal oscillations, and hence no gravitational wave radiation will be emitted. Therefore, in this study the author proposes that the radius is 300 Km.</p>
    </sec>
    <sec id="sec2">
      <title>2. The Spectrum of Toroidal Oscillations</title>
      <p>Toroidal oscillations of rotating celestial objects draw the attention of many astrophysicists and is the subject of much research nowadays [<xref ref-type="bibr" rid="B5">5</xref>][<xref ref-type="bibr" rid="B6">6</xref>]. </p>
      <p>We consider the small-amplitude oscillations of a stellar spherical object due to perturbations that can be described in terms of the spherical harmonics <inline-formula><mml:math><mml:mrow><mml:mi> Y </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> ϑ </mml:mi><mml:mo> , </mml:mo><mml:mi> ϕ </mml:mi></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> given by [<xref ref-type="bibr" rid="B7">7</xref>]:</p>
      <disp-formula id="FD1">
        <label>(1)</label>
        <mml:math>
          <mml:mrow>
            <mml:msubsup>
              <mml:mi>Y</mml:mi>
              <mml:mi>l</mml:mi>
              <mml:mi>m</mml:mi>
            </mml:msubsup>
            <mml:mrow>
              <mml:mo>(</mml:mo>
              <mml:mrow>
                <mml:mi>ϑ</mml:mi>
                <mml:mo>,</mml:mo>
                <mml:mi>ϕ</mml:mi>
              </mml:mrow>
              <mml:mo>)</mml:mo>
            </mml:mrow>
            <mml:mo>=</mml:mo>
            <mml:msup>
              <mml:mrow>
                <mml:mrow>
                  <mml:mo>(</mml:mo>
                  <mml:mrow>
                    <mml:mo>−</mml:mo>
                    <mml:mn>1</mml:mn>
                  </mml:mrow>
                  <mml:mo>)</mml:mo>
                </mml:mrow>
              </mml:mrow>
              <mml:mi>m</mml:mi>
            </mml:msup>
            <mml:msub>
              <mml:mi>c</mml:mi>
              <mml:mrow>
                <mml:mi>l</mml:mi>
                <mml:mi>m</mml:mi>
              </mml:mrow>
            </mml:msub>
            <mml:msubsup>
              <mml:mi>P</mml:mi>
              <mml:mi>l</mml:mi>
              <mml:mi>m</mml:mi>
            </mml:msubsup>
            <mml:mrow>
              <mml:mo>(</mml:mo>
              <mml:mrow>
                <mml:mi>cos</mml:mi>
                <mml:mi>ϑ</mml:mi>
              </mml:mrow>
              <mml:mo>)</mml:mo>
            </mml:mrow>
            <mml:mi>exp</mml:mi>
            <mml:mrow>
              <mml:mo>(</mml:mo>
              <mml:mrow>
                <mml:mi>i</mml:mi>
                <mml:mi>m</mml:mi>
                <mml:mi>ϕ</mml:mi>
              </mml:mrow>
              <mml:mo>)</mml:mo>
            </mml:mrow>
          </mml:mrow>
        </mml:math>
      </disp-formula>
      <p>where, <italic>ϑ</italic> is the co-latitude (measured from the z-axis) and <italic>ϕ</italic> is the longitude measured from the x axis in the equator. <inline-formula><mml:math><mml:mrow><mml:msubsup><mml:mi> P </mml:mi><mml:mi> l </mml:mi><mml:mi> m </mml:mi></mml:msubsup></mml:mrow></mml:math></inline-formula> is the associate Legendre function of order (<inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> , </mml:mo><mml:mi> m </mml:mi></mml:mrow></mml:math></inline-formula> ), <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> c </mml:mi><mml:mrow><mml:mi> l </mml:mi><mml:mi> m </mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> is the normalization constant.</p>
      <p>For studying the stellar oscillations, it is necessary to solve the equation of motion of the perturbation and to define its spectrum to determine the amplitude of the oscillation. Stellar objects are usually treated as a continuum of gas (or fluid) [<xref ref-type="bibr" rid="B6">6</xref>][<xref ref-type="bibr" rid="B8">8</xref>], where their properties can be specified as functions of position <italic><bold>r</bold></italic> and time <italic>t</italic> (these include local density <italic>ρ</italic> (<italic>r</italic>, <italic>t</italic>), local pressure <italic>p</italic> (<italic>r</italic>, <italic>t</italic>) and local instantaneous velocity <italic><bold>v</bold></italic> (<italic>r</italic>, <italic>t</italic>)). In the <italic>Eulerian</italic> description <italic><bold>r</bold></italic> denotes the position vector to a given point in space as seen by stationary observer. It is also convenient to use the <italic>Lagrangian</italic> description where the observer follows the motion of the gas.</p>
      <p>More often stellar objects are rotating objects; hence, it is straight forward to notice that rotation might affect the observed frequencies. We assume that the angular frequency Ω is uniform and consider an oscillation with a frequency <italic>ω</italic> independent of <italic>m</italic>, in the frame rotating with the object. Let a coordinate system in this frame with coordinates <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:msup><mml:mi> r </mml:mi><mml:mo> ′ </mml:mo></mml:msup><mml:mo> , </mml:mo><mml:msup><mml:mi> ϑ </mml:mi><mml:mo> ′ </mml:mo></mml:msup><mml:mo> , </mml:mo><mml:msup><mml:mi> ϕ </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> which are related to the coordinates <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> r </mml:mi><mml:mo> , </mml:mo><mml:mi> ϑ </mml:mi><mml:mo> , </mml:mo><mml:mi> ϕ </mml:mi></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> in an inertial frame through, <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:msup><mml:mi> r </mml:mi><mml:mo> ′ </mml:mo></mml:msup><mml:mo> , </mml:mo><mml:msup><mml:mi> ϑ </mml:mi><mml:mo> ′ </mml:mo></mml:msup><mml:mo> , </mml:mo><mml:msup><mml:mi> ϕ </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:mrow><mml:mo> ) </mml:mo></mml:mrow><mml:mo> = </mml:mo><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> r </mml:mi><mml:mo> , </mml:mo><mml:mi> ϑ </mml:mi><mml:mo> , </mml:mo><mml:mi> ϕ </mml:mi><mml:mo> − </mml:mo><mml:mi> Ω </mml:mi><mml:mi> t </mml:mi></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> . It follows that, in the rotating frame, the perturbation depends on <inline-formula><mml:math display="inline"><mml:msup><mml:mi> ϕ </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:math></inline-formula> and <italic>t</italic> as <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> cos </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> m </mml:mi><mml:msup><mml:mi> ϕ </mml:mi><mml:mo> ′ </mml:mo></mml:msup><mml:mo> − </mml:mo><mml:msub><mml:mi> ω </mml:mi><mml:mn> 0 </mml:mn></mml:msub><mml:mi> t </mml:mi></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> ; hence the dependence in the inertial frame is <inline-formula><mml:math><mml:mrow><mml:mi> cos </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> m </mml:mi><mml:mi> ϕ </mml:mi><mml:mo> − </mml:mo><mml:msub><mml:mi> ω </mml:mi><mml:mi> m </mml:mi></mml:msub><mml:mi> t </mml:mi></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> where <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> m </mml:mi></mml:msub><mml:mo> = </mml:mo><mml:msub><mml:mi> ω </mml:mi><mml:mn> 0 </mml:mn></mml:msub><mml:mo> + </mml:mo><mml:mi> m </mml:mi><mml:mtext>   </mml:mtext><mml:mi> Ω </mml:mi></mml:mrow></mml:math></inline-formula> . Thus, an observer in the inertial frame finds that the frequency is split uniformly [<xref ref-type="bibr" rid="B8">8</xref>] according to <italic>m</italic>.</p>
      <p>The toroidal (sometimes called torsional) oscillations, typically occurring in fast rotating spherically symmetric stellar objects, are non-radial, shear-like oscillations where the displacement is primarily in the azimuthal direction. This type of oscillation mode arises in the core of our proposed anti-universe model, via two kind of mechanisms: 1) The first one is characterized by those displacements that lie on the surface of the constant radius’s core of the anti-universe, similar to r-modes or inertial modes of oscillations usually studied in rotating stars [<xref ref-type="bibr" rid="B5">5</xref>][<xref ref-type="bibr" rid="B9">9</xref>], 2) The second exists at the surface of the core due to the thin plasma layer formed by the negatively-charged heavy anti-protons together with the positively-charged light positrons [<xref ref-type="bibr" rid="B10">10</xref>] and which are regarded as two-fluid plasma model. The geometry of the model leads to toroidal Alfven eigen modes arising from magnetic field geometry, similar to that in fusion devices like-tokamaks [<xref ref-type="bibr" rid="B11">11</xref>]. </p>
      <p>The toroidal spectrum generated refers to the eigen frequencies of these oscillation modes and is dependent on the system’s physical properties, for example rotation, density and magnetic field. The spectrum can be found by solving the linearized equation of motion for perturbations in the two systems discussed above, namely, 1) Bulk oscillations, and 2) surface plasma oscillations.</p>
      <sec id="sec2dot1">
        <title>2.1. Bulk Oscillations</title>
        <p>The bulk (core) can be considered as neutral relativistic fluid. We assume a small perturbation or displacement<italic>ζ</italic> of the form,</p>
        <disp-formula id="FD2">
          <label>(2)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mi>ζ</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mstyle mathvariant="bold" mathsize="normal">
                    <mml:mi>r</mml:mi>
                  </mml:mstyle>
                  <mml:mo>,</mml:mo>
                  <mml:mi>t</mml:mi>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>=</mml:mo>
              <mml:mi>ζ</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mi>r</mml:mi>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mi>exp</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mo>−</mml:mo>
                  <mml:mi>i</mml:mi>
                  <mml:mi>ω</mml:mi>
                  <mml:mtext>
                     
                  </mml:mtext>
                  <mml:mi>t</mml:mi>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <italic>ω</italic> is the eigen frequency of the mode (oscillation frequency in rotating frame). For toroidal modes the displacement is primarily in the azimuthal direction (<inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ζ </mml:mi><mml:mi> φ </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> in spherical coordinates). Substitute Equation (2) into Euler’s equation for ideal fluid in a rotating reference frame, we obtain the linearized momentum equation [<xref ref-type="bibr" rid="B6">6</xref>][<xref ref-type="bibr" rid="B10">10</xref>],</p>
        <disp-formula id="FD3">
          <label>(3)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mo>−</mml:mo>
              <mml:msup>
                <mml:mi>ω</mml:mi>
                <mml:mn>2</mml:mn>
              </mml:msup>
              <mml:mi>ζ</mml:mi>
              <mml:mo>+</mml:mo>
              <mml:mn>2</mml:mn>
              <mml:mi>i</mml:mi>
              <mml:mi>ω</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mi>Ω</mml:mi>
                  <mml:mo>×</mml:mo>
                  <mml:mi>ζ</mml:mi>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>=</mml:mo>
              <mml:mo>−</mml:mo>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:msub>
                        <mml:mi>ρ</mml:mi>
                        <mml:mn>0</mml:mn>
                      </mml:msub>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>∇</mml:mo>
              <mml:msup>
                <mml:mi>P</mml:mi>
                <mml:mo>′</mml:mo>
              </mml:msup>
              <mml:mo>−</mml:mo>
              <mml:mo>∇</mml:mo>
              <mml:msup>
                <mml:mi>φ</mml:mi>
                <mml:mo>′</mml:mo>
              </mml:msup>
              <mml:mo>+</mml:mo>
              <mml:mi>g</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:msup>
                      <mml:mi>ρ</mml:mi>
                      <mml:mo>′</mml:mo>
                    </mml:msup>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:msub>
                        <mml:mi>ρ</mml:mi>
                        <mml:mn>0</mml:mn>
                      </mml:msub>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math display="inline"><mml:msup><mml:mi> p </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:math></inline-formula> is the perturbation pressure, <inline-formula><mml:math display="inline"><mml:msup><mml:mi> φ </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:math></inline-formula> is the gravitational perturbation, <inline-formula><mml:math display="inline"><mml:msup><mml:mi> ρ </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:math></inline-formula> is the density perturbation, <italic>g</italic> is the gravitational acceleration and Ω is the rotation velocity. For toroidal modes, the radial displacement is often negligible, and perturbation is divergence-free (<inline-formula><mml:math display="inline"><mml:mrow><mml:mo> ∇ </mml:mo><mml:mo> ⋅ </mml:mo><mml:mi> ζ </mml:mi><mml:mo> = </mml:mo><mml:mn> 0 </mml:mn></mml:mrow></mml:math></inline-formula> ). The second term in the L. H. S. of Equation (3) is the Coriolis force which is considered as the restoring force for the oscillations and lifts the degeneracy in<italic>m</italic> due to rotation. In rotating stellar objects where oscillations dominate, the r-mode for ultra-fast rotation is considered as one of the most important types of modes relevant to astrophysical studies and having oscillation frequencies proportion to the rotation velocity given by [<xref ref-type="bibr" rid="B6">6</xref>],</p>
        <disp-formula id="FD4">
          <label>(4)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>ω</mml:mi>
                <mml:mi>r</mml:mi>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mrow>
                <mml:mrow>
                  <mml:mn>2</mml:mn>
                  <mml:mi>Ω</mml:mi>
                  <mml:mi>m</mml:mi>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:mi>l</mml:mi>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mi>l</mml:mi>
                      <mml:mo>+</mml:mo>
                      <mml:mn>1</mml:mn>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>in the rotating frame [<xref ref-type="bibr" rid="B8">8</xref>], where <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> r </mml:mi></mml:msub><mml:mo> = </mml:mo><mml:msub><mml:mi> ω </mml:mi><mml:mrow><mml:mi> i </mml:mi><mml:mi> n </mml:mi><mml:mi> e </mml:mi><mml:mi> r </mml:mi></mml:mrow></mml:msub><mml:mo> + </mml:mo><mml:mi> Ω </mml:mi><mml:mi> m </mml:mi></mml:mrow></mml:math></inline-formula> [<xref ref-type="bibr" rid="B6">6</xref>], and is driven by the Coriolis force in the bulk of the rotating core. The r-mode eigen frequencies in the inertial frame and after considering the relativistic effect, is given by,</p>
        <disp-formula id="FD5">
          <label>(5)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>ω</mml:mi>
                <mml:mi>B</mml:mi>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mi>Ω</mml:mi>
              <mml:mi>m</mml:mi>
              <mml:mo>−</mml:mo>
              <mml:mrow>
                <mml:mrow>
                  <mml:mn>2</mml:mn>
                  <mml:mi>Ω</mml:mi>
                  <mml:mi>m</mml:mi>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mi>l</mml:mi>
                      <mml:mrow>
                        <mml:mo>(</mml:mo>
                        <mml:mrow>
                          <mml:mi>l</mml:mi>
                          <mml:mo>+</mml:mo>
                          <mml:mn>1</mml:mn>
                        </mml:mrow>
                        <mml:mo>)</mml:mo>
                      </mml:mrow>
                      <mml:mi>γ</mml:mi>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math><mml:mi> γ </mml:mi></mml:math></inline-formula> is the Lorentz factor <inline-formula><mml:math><mml:mrow><mml:mi> γ </mml:mi><mml:mo> = </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> − </mml:mo><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mrow><mml:mi> v </mml:mi><mml:mo> / </mml:mo><mml:mi> c </mml:mi></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mn> 2 </mml:mn></mml:msup></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:mrow></mml:msup></mml:mrow></mml:mrow></mml:mrow></mml:math></inline-formula> , and <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> B </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> is the bulk frequency due to relativistic rotations in inertial frame.</p>
      </sec>
      <sec id="sec2dot2">
        <title>2.2. Surface Plasma Oscillations</title>
        <p>At the surface where the anti-hydrogen atoms are ionized and a thin plasma layer of negatively-charged anti-protons and positively-charged positrons are formed, the magneto-hydrodynamic (MHD) effects play a significant role. The linearized (MHD) equation for the plasma is given by [<xref ref-type="bibr" rid="B7">7</xref>][<xref ref-type="bibr" rid="B10">10</xref>],</p>
        <disp-formula id="FD6">
          <label>(6)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mi>ρ</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mrow>
                      <mml:msup>
                        <mml:mo>∂</mml:mo>
                        <mml:mn>2</mml:mn>
                      </mml:msup>
                      <mml:mi>ζ</mml:mi>
                    </mml:mrow>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:msup>
                        <mml:mo>∂</mml:mo>
                        <mml:mn>2</mml:mn>
                      </mml:msup>
                      <mml:mi>t</mml:mi>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>=</mml:mo>
              <mml:mo>−</mml:mo>
              <mml:mo>∇</mml:mo>
              <mml:msup>
                <mml:mi>P</mml:mi>
                <mml:mo>′</mml:mo>
              </mml:msup>
              <mml:mo>+</mml:mo>
              <mml:mrow>
                <mml:mn>1</mml:mn>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:msub>
                    <mml:mi>μ</mml:mi>
                    <mml:mn>0</mml:mn>
                  </mml:msub>
                </mml:mrow>
              </mml:mrow>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mo>∇</mml:mo>
                  <mml:mo>×</mml:mo>
                  <mml:mstyle mathvariant="bold" mathsize="normal">
                    <mml:msup>
                      <mml:mi>B</mml:mi>
                      <mml:mo>′</mml:mo>
                    </mml:msup>
                  </mml:mstyle>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>×</mml:mo>
              <mml:msub>
                <mml:mstyle mathvariant="bold" mathsize="normal">
                  <mml:mi>B</mml:mi>
                </mml:mstyle>
                <mml:mn>0</mml:mn>
              </mml:msub>
              <mml:mo>+</mml:mo>
              <mml:mrow>
                <mml:mn>1</mml:mn>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:msub>
                    <mml:mi>μ</mml:mi>
                    <mml:mn>0</mml:mn>
                  </mml:msub>
                </mml:mrow>
              </mml:mrow>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mo>∇</mml:mo>
                  <mml:mo>×</mml:mo>
                  <mml:msub>
                    <mml:mstyle mathvariant="bold" mathsize="normal">
                      <mml:mi>B</mml:mi>
                    </mml:mstyle>
                    <mml:mn>0</mml:mn>
                  </mml:msub>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>×</mml:mo>
              <mml:mstyle mathvariant="bold" mathsize="normal">
                <mml:msup>
                  <mml:mi>B</mml:mi>
                  <mml:mo>′</mml:mo>
                </mml:msup>
              </mml:mstyle>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> B </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> is the background-equilibrium magnetic field, <inline-formula><mml:math display="inline"><mml:mstyle mathvariant="bold" mathsize="normal"><mml:msup><mml:mi> B </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:mstyle></mml:math></inline-formula> is the perturbed magnetic field, related to <inline-formula><mml:math display="inline"><mml:mi> ζ </mml:mi></mml:math></inline-formula> via, <inline-formula><mml:math display="inline"><mml:mrow><mml:mstyle mathvariant="bold" mathsize="normal"><mml:msup><mml:mi> B </mml:mi><mml:mo> ′ </mml:mo></mml:msup></mml:mstyle><mml:mo> = </mml:mo><mml:mo> ∇ </mml:mo><mml:mo> × </mml:mo><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> ζ </mml:mi><mml:mo> × </mml:mo><mml:msub><mml:mstyle mathvariant="bold" mathsize="normal"><mml:mi> B </mml:mi></mml:mstyle><mml:mn> 0 </mml:mn></mml:msub></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> , and <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> μ </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> is the permeability of free space. The plasma produces “toroidal Alfven modes”, driven by the plasma’s magnetic field with frequencies determined by the Alfven speed [<xref ref-type="bibr" rid="B10">10</xref>],</p>
        <disp-formula id="FD7">
          <label>(7)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>v</mml:mi>
                <mml:mi>A</mml:mi>
              </mml:msub>
              <mml:mo>=</mml:mo>
              <mml:mrow>
                <mml:mrow>
                  <mml:msub>
                    <mml:mi>B</mml:mi>
                    <mml:mn>0</mml:mn>
                  </mml:msub>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:msup>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mo>(</mml:mo>
                        <mml:mrow>
                          <mml:mn>4</mml:mn>
                          <mml:mi>π</mml:mi>
                          <mml:msub>
                            <mml:mi>ρ</mml:mi>
                            <mml:mrow>
                              <mml:mi>p</mml:mi>
                              <mml:mi>l</mml:mi>
                              <mml:mi>a</mml:mi>
                              <mml:mi>s</mml:mi>
                              <mml:mi>m</mml:mi>
                              <mml:mi>a</mml:mi>
                            </mml:mrow>
                          </mml:msub>
                        </mml:mrow>
                        <mml:mo>)</mml:mo>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mn>1</mml:mn>
                        <mml:mo>/</mml:mo>
                        <mml:mn>2</mml:mn>
                      </mml:mrow>
                    </mml:mrow>
                  </mml:msup>
                </mml:mrow>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where,</p>
        <disp-formula id="FD8">
          <label>(8)</label>
          <mml:math>
            <mml:mrow>
              <mml:msub>
                <mml:mi>ρ</mml:mi>
                <mml:mrow>
                  <mml:mi>p</mml:mi>
                  <mml:mi>l</mml:mi>
                  <mml:mi>a</mml:mi>
                  <mml:mi>s</mml:mi>
                  <mml:mi>m</mml:mi>
                  <mml:mi>a</mml:mi>
                </mml:mrow>
              </mml:msub>
              <mml:mo>=</mml:mo>
              <mml:msub>
                <mml:mi>n</mml:mi>
                <mml:mrow>
                  <mml:mi>a</mml:mi>
                  <mml:mi>n</mml:mi>
                  <mml:mi>t</mml:mi>
                  <mml:mi>i</mml:mi>
                  <mml:mtext>-</mml:mtext>
                  <mml:mi>p</mml:mi>
                </mml:mrow>
              </mml:msub>
              <mml:msub>
                <mml:mi>m</mml:mi>
                <mml:mrow>
                  <mml:mi>a</mml:mi>
                  <mml:mi>n</mml:mi>
                  <mml:mi>t</mml:mi>
                  <mml:mi>i</mml:mi>
                  <mml:mtext>-</mml:mtext>
                  <mml:mi>p</mml:mi>
                </mml:mrow>
              </mml:msub>
              <mml:mo>+</mml:mo>
              <mml:msub>
                <mml:mi>n</mml:mi>
                <mml:mrow>
                  <mml:mi>p</mml:mi>
                  <mml:mi>o</mml:mi>
                  <mml:mi>s</mml:mi>
                </mml:mrow>
              </mml:msub>
              <mml:msub>
                <mml:mi>m</mml:mi>
                <mml:mrow>
                  <mml:mi>p</mml:mi>
                  <mml:mi>o</mml:mi>
                  <mml:mi>s</mml:mi>
                </mml:mrow>
              </mml:msub>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>and <inline-formula><mml:math><mml:mi> n </mml:mi></mml:math></inline-formula> , <inline-formula><mml:math><mml:mi> m </mml:mi></mml:math></inline-formula> are the number densities &amp; the masses respectively. The frequency of the toroidal Alfven mode is,</p>
        <p><inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> A </mml:mi></mml:msub><mml:mo> ≈ </mml:mo><mml:msub><mml:mi> v </mml:mi><mml:mi> A </mml:mi></mml:msub><mml:msub><mml:mi> k </mml:mi><mml:mo> ∅ </mml:mo></mml:msub></mml:mrow></mml:math></inline-formula> , where <inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> k </mml:mi><mml:mo> ∅ </mml:mo></mml:msub><mml:mo> = </mml:mo><mml:mrow><mml:mi> m </mml:mi><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow></mml:mrow></mml:math></inline-formula> is the azimuthal wave number. Thus, the toroidal Alfven frequency is, given by [<xref ref-type="bibr" rid="B10">10</xref>],</p>
        <disp-formula id="FD9">
          <label>(9)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>ω</mml:mi>
                <mml:mi>A</mml:mi>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mrow>
                <mml:mrow>
                  <mml:mi>m</mml:mi>
                  <mml:msub>
                    <mml:mi>B</mml:mi>
                    <mml:mn>0</mml:mn>
                  </mml:msub>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mi>R</mml:mi>
              </mml:mrow>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mn>4</mml:mn>
                      <mml:mi>π</mml:mi>
                      <mml:msub>
                        <mml:mi>ρ</mml:mi>
                        <mml:mrow>
                          <mml:mi>p</mml:mi>
                          <mml:mi>l</mml:mi>
                          <mml:mi>a</mml:mi>
                          <mml:mi>s</mml:mi>
                          <mml:mi>m</mml:mi>
                          <mml:mi>a</mml:mi>
                        </mml:mrow>
                      </mml:msub>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mn>2</mml:mn>
                  </mml:mrow>
                </mml:mrow>
              </mml:msup>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>however, a simplified formula for the toroidal plasma Alfven angular frequency [<xref ref-type="bibr" rid="B10">10</xref>][<xref ref-type="bibr" rid="B12">12</xref>],</p>
        <disp-formula id="FD10">
          <label>(10)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>ω</mml:mi>
                <mml:mi>A</mml:mi>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mi>l</mml:mi>
                      <mml:mrow>
                        <mml:mo>(</mml:mo>
                        <mml:mrow>
                          <mml:mi>l</mml:mi>
                          <mml:mo>+</mml:mo>
                          <mml:mn>1</mml:mn>
                        </mml:mrow>
                        <mml:mo>)</mml:mo>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mn>2</mml:mn>
                  </mml:mrow>
                </mml:mrow>
              </mml:msup>
              <mml:mrow>
                <mml:mi>c</mml:mi>
                <mml:mo>/</mml:mo>
                <mml:mi>R</mml:mi>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>is used when <italic>v</italic> approaches <italic>c</italic> and for strong magnetic field <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> B </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> . This limit can be justified if the plasma is in a force-free (charge-starved regime) leading to wave propagation near the speed of light, which is common in relativistic astrophysics plasmas such as pulsar magnetospheres (e.g. [<xref ref-type="bibr" rid="B12">12</xref>][<xref ref-type="bibr" rid="B13">13</xref>]). This simplified formula was derived in the relativistic limit of magnetohydrodynamics (MHD) when <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> v </mml:mi><mml:mi> A </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> approaches <italic>c</italic> [<xref ref-type="bibr" rid="B6">6</xref>]. This occurs when the magnetic energy density dominates over the plasma’s effective energy density, where the factor <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> l </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> l </mml:mi><mml:mo> + </mml:mo><mml:mn> 1 </mml:mn></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:mrow></mml:msup></mml:mrow><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow></mml:mrow></mml:math></inline-formula> comes from the angular wave number in spherical geometry for toroidal modes (from the spherical harmonic Laplacian eigen values) [<xref ref-type="bibr" rid="B14">14</xref>]. The extreme rotation and the interactions between the bulk and the plasma at the surface lead to hybrid modes. The plasma layer couples the bulk mode with the plasma Alfven mode via boundary conditions at the surface (<italic>r</italic>= <italic>R</italic>), where the displacement<italic>ζ</italic> must be continuous and the magnetic stress balances the fluid stress.</p>
        <p>The total frequency is then, given approximately by,</p>
        <disp-formula id="FD11">
          <label>(11)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mi>ω</mml:mi>
              <mml:mo>=</mml:mo>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:msubsup>
                        <mml:mi>ω</mml:mi>
                        <mml:mi>B</mml:mi>
                        <mml:mn>2</mml:mn>
                      </mml:msubsup>
                      <mml:mo>+</mml:mo>
                      <mml:msubsup>
                        <mml:mi>ω</mml:mi>
                        <mml:mi>A</mml:mi>
                        <mml:mn>2</mml:mn>
                      </mml:msubsup>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mn>2</mml:mn>
                  </mml:mrow>
                </mml:mrow>
              </mml:msup>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>assuming weak coupling between the bulk and the plasma. The frequency in the inertial frame is therefore, given by,</p>
        <disp-formula id="FD12">
          <label>(12)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>ω</mml:mi>
                <mml:mrow>
                  <mml:mi>i</mml:mi>
                  <mml:mi>n</mml:mi>
                  <mml:mi>e</mml:mi>
                  <mml:mi>r</mml:mi>
                </mml:mrow>
              </mml:msub>
              <mml:mo>=</mml:mo>
              <mml:mi>ω</mml:mi>
              <mml:mo>+</mml:mo>
              <mml:mrow>
                <mml:mo>|</mml:mo>
                <mml:mi>m</mml:mi>
                <mml:mo>|</mml:mo>
              </mml:mrow>
              <mml:mi>Ω</mml:mi>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>accounting for Doppler shift due to rotation.</p>
      </sec>
      <sec id="sec2dot3">
        <title>2.3. Spectrum Calculations</title>
        <p>To calculate the spectrum of toroidal oscillations for the system of the spherically compact object made of anti-hydrogen atoms, we assume the following parameters for the compact object:</p>
        <p>Mass <italic>M</italic> is 100 solar masses ≈ 1.989 × 10<sup>32</sup> kg</p>
        <p>Radius <italic>R</italic> about 300 km = 3 × 10<sup>5</sup> m.</p>
        <p>Tangential velocity at the equatorial plane of 0.99<italic>c</italic>.</p>
        <p>Angular velocity <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> Ω </mml:mi><mml:mo> = </mml:mo><mml:mrow><mml:mi> v </mml:mi><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow><mml:mo> ≈ </mml:mo><mml:mn> 0.99 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mn> 3 </mml:mn></mml:msup><mml:mrow><mml:mrow><mml:mtext> rad </mml:mtext></mml:mrow><mml:mo> / </mml:mo><mml:mtext> s </mml:mtext></mml:mrow></mml:mrow></mml:math></inline-formula> .</p>
        <p>Lorentz factor <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> γ </mml:mi><mml:mo> = </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> − </mml:mo><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mrow><mml:mi> v </mml:mi><mml:mo> / </mml:mo><mml:mi> c </mml:mi></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mn> 2 </mml:mn></mml:msup></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:mrow></mml:msup></mml:mrow></mml:mrow><mml:mo> ≈ </mml:mo><mml:mn> 7.09 </mml:mn></mml:mrow></mml:math></inline-formula></p>
        <p>Plasma layer: Composed of anti-protons (<inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> m </mml:mi><mml:mrow><mml:mi> a </mml:mi><mml:mi> n </mml:mi><mml:mi> t </mml:mi><mml:mi> i </mml:mi><mml:mtext> - </mml:mtext><mml:mi> p </mml:mi></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:mn> 1.673 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 27 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> kg </mml:mtext></mml:mrow></mml:math></inline-formula> ), and positrons (<inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> m </mml:mi><mml:mrow><mml:mi> p </mml:mi><mml:mi> o </mml:mi><mml:mi> s </mml:mi></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:mn> 9.1 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 31 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> kg </mml:mtext></mml:mrow></mml:math></inline-formula> ), a charge-neutral plasma with equal number densities <inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> n </mml:mi><mml:mrow><mml:mi> a </mml:mi><mml:mi> n </mml:mi><mml:mi> t </mml:mi><mml:mi> i </mml:mi><mml:mtext> - </mml:mtext><mml:mi> p </mml:mi></mml:mrow></mml:msub><mml:mo> = </mml:mo><mml:msub><mml:mi> n </mml:mi><mml:mrow><mml:mi> p </mml:mi><mml:mi> o </mml:mi><mml:mi> s </mml:mi></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mn> 20 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:msup><mml:mtext> m </mml:mtext><mml:mrow><mml:mo> − </mml:mo><mml:mn> 3 </mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> , yielding plasma density <inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> ρ </mml:mi><mml:mrow><mml:mi> p </mml:mi><mml:mi> l </mml:mi><mml:mi> a </mml:mi><mml:mi> s </mml:mi><mml:mi> m </mml:mi><mml:mi> a </mml:mi></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:mn> 1.67 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 7 </mml:mn></mml:mrow></mml:msup><mml:mrow><mml:mrow><mml:mtext> kg </mml:mtext></mml:mrow><mml:mo> / </mml:mo><mml:mrow><mml:msup><mml:mtext> m </mml:mtext><mml:mn> 3 </mml:mn></mml:msup></mml:mrow></mml:mrow></mml:mrow></mml:math></inline-formula> .</p>
        <p>A toroidal magnetic field <inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> B </mml:mi><mml:mn> 0 </mml:mn></mml:msub><mml:mo> = </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mn> 6 </mml:mn></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> T </mml:mtext></mml:mrow></mml:math></inline-formula> .</p>
        <p>Bulk density: Average density <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> ρ </mml:mi><mml:mo> = </mml:mo><mml:mrow><mml:mi> M </mml:mi><mml:mo> / </mml:mo><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mrow><mml:mn> 4 </mml:mn><mml:mo> / </mml:mo><mml:mn> 3 </mml:mn></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow><mml:mi> π </mml:mi><mml:msup><mml:mi> R </mml:mi><mml:mn> 3 </mml:mn></mml:msup></mml:mrow></mml:mrow><mml:mo> ≈ </mml:mo><mml:mn> 1.7 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mn> 15 </mml:mn></mml:mrow></mml:msup><mml:mrow><mml:mrow><mml:mtext> kg </mml:mtext></mml:mrow><mml:mo> / </mml:mo><mml:mrow><mml:msup><mml:mtext> m </mml:mtext><mml:mn> 3 </mml:mn></mml:msup></mml:mrow></mml:mrow></mml:mrow></mml:math></inline-formula> .</p>
        <p>The results of the spectrum calculations are listed in <bold>Table 1</bold>, for <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:math></inline-formula> to 3 and <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mo> − </mml:mo><mml:mn> 2 </mml:mn><mml:mo> , </mml:mo><mml:mo> − </mml:mo><mml:mn> 1 </mml:mn><mml:mo> , </mml:mo><mml:mn> 0 </mml:mn><mml:mo> , </mml:mo><mml:mn> 1 </mml:mn><mml:mo> , </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> .</p>
        <p>The table contains the calculated frequencies of the toroidal bulk, Alfven, hybrid modes, to provide insights into the oscillatory behavior of the relativistic rotating compact anti-universe. The model assumes a uniform density, simplified</p>
        <p><bold>Table 1.</bold>The values of toroidal oscillation frequencies in (rad/s), the bulk modes <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> B </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> , plasma Alfven modes <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> A </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> , and hybrid modes <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> ω </mml:mi><mml:mi> H </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> , for <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:math></inline-formula> to 3 and <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mo> − </mml:mo><mml:mn> 2 </mml:mn><mml:mo> , </mml:mo><mml:mo> − </mml:mo><mml:mn> 1 </mml:mn><mml:mo> , </mml:mo><mml:mn> 0 </mml:mn><mml:mo> , </mml:mo><mml:mn> 1 </mml:mn><mml:mo> , </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> .</p>
        <table-wrap id="tbl1">
          <label>Table 1</label>
          <table>
            <tbody>
              <tr>
                <td>
                  <inline-formula>
                    <mml:math>
                      <mml:mi>l</mml:mi>
                    </mml:math>
                  </inline-formula>
                </td>
                <td>
                  <inline-formula>
                    <mml:math>
                      <mml:mi>m</mml:mi>
                    </mml:math>
                  </inline-formula>
                </td>
                <td>
                  <inline-formula>
                    <mml:math>
                      <mml:mrow>
                        <mml:msub>
                          <mml:mi>ω</mml:mi>
                          <mml:mi>B</mml:mi>
                        </mml:msub>
                      </mml:mrow>
                    </mml:math>
                  </inline-formula>
                </td>
                <td>
                  <inline-formula>
                    <mml:math>
                      <mml:mrow>
                        <mml:msub>
                          <mml:mi>ω</mml:mi>
                          <mml:mi>A</mml:mi>
                        </mml:msub>
                      </mml:mrow>
                    </mml:math>
                  </inline-formula>
                </td>
                <td>
                  <inline-formula>
                    <mml:math>
                      <mml:mrow>
                        <mml:msub>
                          <mml:mi>ω</mml:mi>
                          <mml:mi>H</mml:mi>
                        </mml:msub>
                      </mml:mrow>
                    </mml:math>
                  </inline-formula>
                </td>
              </tr>
              <tr>
                <td>1</td>
                <td>−1</td>
                <td>850</td>
                <td>1414</td>
                <td>1650</td>
              </tr>
              <tr>
                <td>1</td>
                <td>0</td>
                <td>0</td>
                <td>1414</td>
                <td>1414</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>850</td>
                <td>1414</td>
                <td>1650</td>
              </tr>
              <tr>
                <td>2</td>
                <td>−2</td>
                <td>1887</td>
                <td>2450</td>
                <td>3092</td>
              </tr>
              <tr>
                <td>2</td>
                <td>−1</td>
                <td>943</td>
                <td>2450</td>
                <td>2625</td>
              </tr>
              <tr>
                <td>2</td>
                <td>0</td>
                <td>0</td>
                <td>2450</td>
                <td>2450</td>
              </tr>
              <tr>
                <td>2</td>
                <td>1</td>
                <td>943</td>
                <td>2450</td>
                <td>2625</td>
              </tr>
              <tr>
                <td>2</td>
                <td>2</td>
                <td>1887</td>
                <td>2450</td>
                <td>3092</td>
              </tr>
              <tr>
                <td>3</td>
                <td>−2</td>
                <td>1933</td>
                <td>3464</td>
                <td>3967</td>
              </tr>
              <tr>
                <td>3</td>
                <td>−1</td>
                <td>296</td>
                <td>3464</td>
                <td>3597</td>
              </tr>
              <tr>
                <td>3</td>
                <td>0</td>
                <td>0</td>
                <td>3464</td>
                <td>3464</td>
              </tr>
              <tr>
                <td>3</td>
                <td>1</td>
                <td>967</td>
                <td>3464</td>
                <td>3597</td>
              </tr>
              <tr>
                <td>3</td>
                <td>2</td>
                <td>1933</td>
                <td>3464</td>
                <td>3967</td>
              </tr>
            </tbody>
          </table>
        </table-wrap>
        <p>by weak coupling via the thin plasma layer, and relativistic modification through the Lorentz factor <inline-formula><mml:math><mml:mi> γ </mml:mi></mml:math></inline-formula> , which effectively boosts the inertial effects in the co-rotating frame. The bulk modes are like r-modes in neutron stars, driven by rotation and Coriolis forces. The Alfven modes arise from strong magnetic field tensions in the plasma layer, leading to near-light-speed wave propagation. The hybrid mode is dominated by the stronger component.</p>
        <p>The bulk modes depend strongly on the azimuthal number <inline-formula><mml:math><mml:mi> m </mml:mi></mml:math></inline-formula> and the rotational angular velocity Ω, while frequencies increase with the absolute value of <inline-formula><mml:math><mml:mi> m </mml:mi></mml:math></inline-formula> for a given <inline-formula><mml:math><mml:mi> l </mml:mi></mml:math></inline-formula> reflecting stronger restoring Coriolis force for higher azimuthal orders. The Alfven modes are independent of <inline-formula><mml:math><mml:mi> m </mml:mi></mml:math></inline-formula> (due to the assumed axisymmetric magnetic field) and scale with <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo> [ </mml:mo><mml:mrow><mml:mi> l </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mi> l </mml:mi><mml:mo> + </mml:mo><mml:mn> 1 </mml:mn></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mo> ] </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:mrow></mml:msup></mml:mrow><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow></mml:mrow></mml:math></inline-formula> , yielding higher frequencies for larger <inline-formula><mml:math><mml:mi> l </mml:mi></mml:math></inline-formula> (e.g., 1414 rad/s at <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:math></inline-formula> to 3464 rad/s at <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 3 </mml:mn></mml:mrow></mml:math></inline-formula> ). With <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> v </mml:mi><mml:mi> A </mml:mi></mml:msub><mml:mo> ≈ </mml:mo><mml:mi> c </mml:mi></mml:mrow></mml:math></inline-formula> in this high-<inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> B </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> , low-density plasma, these modes propagate rapidly, resulting in short periods (between 4.4 × 10<sup>−</sup><sup>3</sup> s and 1.8 × 10<sup>−</sup><sup>3</sup> s), consistent with strong-field compact objects like magnetars [<xref ref-type="bibr" rid="B15">15</xref>], and compactness <inline-formula><mml:math><mml:mrow><mml:mi> C </mml:mi><mml:mo> = </mml:mo><mml:mrow><mml:mrow><mml:mi> G </mml:mi><mml:mi> M </mml:mi></mml:mrow><mml:mo> / </mml:mo><mml:mrow><mml:mi> R </mml:mi><mml:msup><mml:mi> c </mml:mi><mml:mn> 2 </mml:mn></mml:msup></mml:mrow></mml:mrow><mml:mo> ≈ </mml:mo><mml:mn> 0.493 </mml:mn></mml:mrow></mml:math></inline-formula> . The hybrid modes have always higher frequencies than both the individual bulk and Alphen modes. </p>
        <p><bold>Table 1</bold> shows that the toroidal oscillation angular velocities vary from 850 to 3967 in rad/s corresponding to approximate frequencies between ~135 Hz to ~632 Hz.</p>
        <p>In general, the frequencies range from ~ 135Hz to ~632Hz, corresponding to periods of ~0.0016 - 0.0074 s <italic>i.e.</italic>, in the millisecond timescales typical for compact object dynamics. </p>
        <p>There are several relevant observatories (ground-based GW interferometers), sensitive to the detection of GW in our range of frequencies, namely: Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) in USA; VIRGO in Italy, collaborating with LIGO for triangulation; KAGRA in Japan; GEO600 in Germany, often used for testing and continuous wave searches.</p>
        <p>Based on astrophysical literature for similar oscillations as in our compact object model, the most prominent toroidal mode for GW emission is typically the <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo></mml:mo><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , <inline-formula><mml:math><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> inertial (r-mode-like) mode. It is the primary channel for the Chandrasekhar-Friedman-Schutz (CFS) instability [<xref ref-type="bibr" rid="B6">6</xref>][<xref ref-type="bibr" rid="B16">16</xref>], leading to potentially strong GW radiation in rotating systems. In our model, this corresponds to the bulk mode at <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo></mml:mo><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , <inline-formula><mml:math><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , with <inline-formula><mml:math><mml:mrow><mml:mi> f </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 300 </mml:mn><mml:mtext>   </mml:mtext><mml:mtext> Hz </mml:mtext></mml:mrow></mml:math></inline-formula> (<inline-formula><mml:math><mml:mrow><mml:mi> ω </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 1887 </mml:mn></mml:mrow></mml:math></inline-formula> rad/s), as it aligns with the frequency range where such modes are expected to saturate and emit continuously if excited (e.g., via accretion or spin-up). This mode is likely more detectable than higher-frequency hybrids (e.g., 492 Hz) because LIGO/Virgo/KAGRA sensitivity is better at ~100 - 300 Hz, where seismic and thermal noise is lower. Alfven modes may couple weakly to GWs due to their magnetic nature, but the hybrid could enhance emission with increasing coupling. However, the bulk mode remains the baseline for prominence in relativistic rotating objects. </p>
      </sec>
    </sec>
    <sec id="sec3">
      <title>3. The Radiated Power and the Gravitational Wave Strain</title>
      <p>For a rotating compact object with toroidal oscillations, GWs are primarily generated by time varying mass quadrupole moments [<xref ref-type="bibr" rid="B17">17</xref>] (or higher multipoles) induced by the oscillations. Since, the spectrum of the toroidal modes computed in Section (2) are non-radial and shear-like, their GW emission is weaker than the spheroidal modes [<xref ref-type="bibr" rid="B18">18</xref>], however, the fast rotation and the relativistic effects largely enhance the GWs signals. As the r-mode discussed in the previous section grows and evolves with time, it emits a continuous gravitational radiation. In this section we shall calculate the order of magnitude of the power radiated. Then, the amplitude of the wave strain <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> h </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> , of the most prominent mode for gravitational wave emission in <bold>Table 1</bold>, will be evaluated, namely, <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo></mml:mo><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> (which was the primary channel for Chandrasekhar-Friedman-Schutz (CFS) instability) that leads to potentially strong GW radiation in rotating systems. This will be followed by the discussion of the possibility of measuring and detecting the GWs with the available devices.</p>
      <sec id="sec3dot1">
        <title>3.1. Power Radiated from the Toroidal R-Mode</title>
        <p>The power radiated by the GWs is given by the mass quadrupole formula [<xref ref-type="bibr" rid="B17">17</xref>] in general relativity overall directions. However, for the r-modes in a rotating celestial object, the quadrupole moment perturbation is driven by the mode displacement equation, given by [<xref ref-type="bibr" rid="B8">8</xref>],</p>
        <disp-formula id="FD13">
          <label>(13)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mi>ζ</mml:mi>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mi>t</mml:mi>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mo>=</mml:mo>
              <mml:mi>α</mml:mi>
              <mml:mi>R</mml:mi>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mi>r</mml:mi>
                        <mml:mo>/</mml:mo>
                        <mml:mi>R</mml:mi>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mi>l</mml:mi>
              </mml:msup>
              <mml:msubsup>
                <mml:mi>Y</mml:mi>
                <mml:mi>l</mml:mi>
                <mml:mi>m</mml:mi>
              </mml:msubsup>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mi>ϑ</mml:mi>
                  <mml:mo>,</mml:mo>
                  <mml:mi>ϕ</mml:mi>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mstyle mathvariant="bold" mathsize="normal">
                <mml:mi>r</mml:mi>
              </mml:mstyle>
              <mml:mo>×</mml:mo>
              <mml:mo>∇</mml:mo>
              <mml:msubsup>
                <mml:mi>Y</mml:mi>
                <mml:mi>l</mml:mi>
                <mml:mi>m</mml:mi>
              </mml:msubsup>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mi>ϑ</mml:mi>
                  <mml:mo>,</mml:mo>
                  <mml:mi>ϕ</mml:mi>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:msup>
                <mml:mtext>e</mml:mtext>
                <mml:mrow>
                  <mml:mo>−</mml:mo>
                  <mml:mi>i</mml:mi>
                  <mml:mi>ω</mml:mi>
                  <mml:mi>t</mml:mi>
                </mml:mrow>
              </mml:msup>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math><mml:mi> α </mml:mi></mml:math></inline-formula> is the dimensionless amplitude of the mode, and <inline-formula><mml:math><mml:mi> ω </mml:mi></mml:math></inline-formula> is the mode frequency. The r-mode instability grows and radiates gravitational waves away from the bulk of the angular momentum of the rapidly rotating compact object [<xref ref-type="bibr" rid="B5">5</xref>]. They are generally defined as solutions of the perturbed fluid equations having, Eulerian-velocity perturbations [<xref ref-type="bibr" rid="B10">10</xref>]. The r-modes evolve with time dependence <inline-formula><mml:math><mml:mrow><mml:msup><mml:mtext> e </mml:mtext><mml:mrow><mml:mi> i </mml:mi><mml:mi> ω </mml:mi><mml:mi> t </mml:mi><mml:mo> − </mml:mo><mml:mrow><mml:mi> t </mml:mi><mml:mo> / </mml:mo><mml:mi> τ </mml:mi></mml:mrow></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> , according to the equations of hydrodynamics [<xref ref-type="bibr" rid="B5">5</xref>][<xref ref-type="bibr" rid="B10">10</xref>] together with the effects of dissipative processes such as shear and bulk viscosities. In our model we ignore these dissipative processes, since they have minor influence on the oscillations, and we consider only the effect of the gravitational radiation of the compact core <inline-formula><mml:math><mml:mrow><mml:mi> τ </mml:mi><mml:mo> ≈ </mml:mo><mml:msub><mml:mi> τ </mml:mi><mml:mi> G </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> . Hence, we express the power as the time derivative of the average energy <inline-formula><mml:math><mml:mover accent="true"><mml:mi> E </mml:mi><mml:mo> ¯ </mml:mo></mml:mover></mml:math></inline-formula> of the mode (as measured in the rotating frame), and is given approximately by [<xref ref-type="bibr" rid="B5">5</xref>],</p>
        <disp-formula id="FD14">
          <label>(14)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mrow>
                <mml:mrow>
                  <mml:mtext>d</mml:mtext>
                  <mml:mover accent="true">
                    <mml:mi>E</mml:mi>
                    <mml:mo>¯</mml:mo>
                  </mml:mover>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:mtext>d</mml:mtext>
                  <mml:mi>t</mml:mi>
                </mml:mrow>
              </mml:mrow>
              <mml:mo>≈</mml:mo>
              <mml:mo>−</mml:mo>
              <mml:mrow>
                <mml:mrow>
                  <mml:mn>2</mml:mn>
                  <mml:mover accent="true">
                    <mml:mi>E</mml:mi>
                    <mml:mo>¯</mml:mo>
                  </mml:mover>
                </mml:mrow>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:msub>
                    <mml:mi>τ</mml:mi>
                    <mml:mi>G</mml:mi>
                  </mml:msub>
                </mml:mrow>
              </mml:mrow>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math display="inline"><mml:mover accent="true"><mml:mi> E </mml:mi><mml:mo> ¯ </mml:mo></mml:mover></mml:math></inline-formula> for <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , is given by (Owen <italic>et al.</italic> 1998),</p>
        <disp-formula id="FD15">
          <label>(15)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mover accent="true">
                <mml:mi>E</mml:mi>
                <mml:mo>¯</mml:mo>
              </mml:mover>
              <mml:mo>=</mml:mo>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mn>2</mml:mn>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:msup>
                <mml:mi>α</mml:mi>
                <mml:mn>2</mml:mn>
              </mml:msup>
              <mml:msup>
                <mml:mtext>Ω</mml:mtext>
                <mml:mn>2</mml:mn>
              </mml:msup>
              <mml:mi>M</mml:mi>
              <mml:msup>
                <mml:mi>R</mml:mi>
                <mml:mn>2</mml:mn>
              </mml:msup>
              <mml:mover accent="true">
                <mml:mi>j</mml:mi>
                <mml:mo>^</mml:mo>
              </mml:mover>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math display="inline"><mml:mover accent="true"><mml:mi> j </mml:mi><mml:mo> ^ </mml:mo></mml:mover></mml:math></inline-formula> is the average angular momentum of the r-mode, which is defined for <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> by [<xref ref-type="bibr" rid="B5">5</xref>],</p>
        <disp-formula id="FD16">
          <label>(16)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mover accent="true">
                <mml:mi>j</mml:mi>
                <mml:mo>^</mml:mo>
              </mml:mover>
              <mml:mo>=</mml:mo>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:mi>M</mml:mi>
                      <mml:msup>
                        <mml:mi>R</mml:mi>
                        <mml:mn>4</mml:mn>
                      </mml:msup>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mstyle displaystyle="true">
                <mml:mrow>
                  <mml:msubsup>
                    <mml:mo>∫</mml:mo>
                    <mml:mn>0</mml:mn>
                    <mml:mi>R</mml:mi>
                  </mml:msubsup>
                  <mml:mrow>
                    <mml:mi>ρ</mml:mi>
                    <mml:msup>
                      <mml:mi>r</mml:mi>
                      <mml:mn>6</mml:mn>
                    </mml:msup>
                    <mml:mtext>d</mml:mtext>
                    <mml:mi>r</mml:mi>
                  </mml:mrow>
                </mml:mrow>
              </mml:mstyle>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>therefore, <inline-formula><mml:math display="inline"><mml:mrow><mml:mover accent="true"><mml:mi> j </mml:mi><mml:mo> ^ </mml:mo></mml:mover><mml:mo> ≈ </mml:mo><mml:mrow><mml:mn> 3 </mml:mn><mml:mo> / </mml:mo><mml:mrow><mml:mn> 28 </mml:mn></mml:mrow></mml:mrow><mml:mi> π </mml:mi></mml:mrow></mml:math></inline-formula> and hence, <inline-formula><mml:math display="inline"><mml:mrow><mml:mover accent="true"><mml:mi> E </mml:mi><mml:mo> ¯ </mml:mo></mml:mover><mml:mo> ≈ </mml:mo><mml:mn> 3 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mn> 35 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> J </mml:mtext></mml:mrow></mml:math></inline-formula>. For the gravitational radiation emission of the r-mode and <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , we use Equation (17) of Ref. [<xref ref-type="bibr" rid="B19">19</xref>], which gives <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mrow><mml:msub><mml:mi> τ </mml:mi><mml:mi> G </mml:mi></mml:msub></mml:mrow></mml:mrow></mml:mrow></mml:math></inline-formula> by,</p>
        <disp-formula id="FD17">
          <label>(17)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mrow>
                <mml:mn>1</mml:mn>
                <mml:mo>/</mml:mo>
                <mml:mrow>
                  <mml:msub>
                    <mml:mi>τ</mml:mi>
                    <mml:mi>G</mml:mi>
                  </mml:msub>
                </mml:mrow>
              </mml:mrow>
              <mml:mo>=</mml:mo>
              <mml:mo>−</mml:mo>
              <mml:mrow>
                <mml:mo>[</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mrow>
                          <mml:mn>32</mml:mn>
                          <mml:mi>π</mml:mi>
                          <mml:mi>G</mml:mi>
                          <mml:msup>
                            <mml:mi>Ω</mml:mi>
                            <mml:mn>6</mml:mn>
                          </mml:msup>
                        </mml:mrow>
                        <mml:mo>/</mml:mo>
                        <mml:mrow>
                          <mml:msup>
                            <mml:mi>c</mml:mi>
                            <mml:mn>7</mml:mn>
                          </mml:msup>
                        </mml:mrow>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                  <mml:mo>×</mml:mo>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mn>1</mml:mn>
                        <mml:mo>/</mml:mo>
                        <mml:mrow>
                          <mml:msup>
                            <mml:mrow>
                              <mml:mrow>
                                <mml:mo>(</mml:mo>
                                <mml:mrow>
                                  <mml:mn>5</mml:mn>
                                  <mml:mo>!</mml:mo>
                                  <mml:mo>!</mml:mo>
                                </mml:mrow>
                                <mml:mo>)</mml:mo>
                              </mml:mrow>
                            </mml:mrow>
                            <mml:mn>2</mml:mn>
                          </mml:msup>
                        </mml:mrow>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                  <mml:mo>×</mml:mo>
                  <mml:msup>
                    <mml:mrow>
                      <mml:mrow>
                        <mml:mo>(</mml:mo>
                        <mml:mrow>
                          <mml:mrow>
                            <mml:mn>4</mml:mn>
                            <mml:mo>/</mml:mo>
                            <mml:mn>3</mml:mn>
                          </mml:mrow>
                        </mml:mrow>
                        <mml:mo>)</mml:mo>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mn>6</mml:mn>
                  </mml:msup>
                </mml:mrow>
                <mml:mo>]</mml:mo>
              </mml:mrow>
              <mml:mstyle displaystyle="true">
                <mml:mrow>
                  <mml:msubsup>
                    <mml:mo>∫</mml:mo>
                    <mml:mn>0</mml:mn>
                    <mml:mi>R</mml:mi>
                  </mml:msubsup>
                  <mml:mrow>
                    <mml:mi>ρ</mml:mi>
                    <mml:msup>
                      <mml:mi>r</mml:mi>
                      <mml:mn>6</mml:mn>
                    </mml:msup>
                    <mml:mtext>d</mml:mtext>
                    <mml:mi>r</mml:mi>
                  </mml:mrow>
                </mml:mrow>
              </mml:mstyle>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>For <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> , <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> / </mml:mo><mml:mrow><mml:msub><mml:mi> τ </mml:mi><mml:mi> G </mml:mi></mml:msub></mml:mrow></mml:mrow><mml:mo> ≈ </mml:mo><mml:mo> − </mml:mo><mml:mn> 38 </mml:mn><mml:mtext>   </mml:mtext><mml:mtext> Hz </mml:mtext></mml:mrow></mml:math></inline-formula> . Substituting in Equation (14), we get,</p>
        <p><inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mi> P </mml:mi><mml:mrow><mml:mn> 22 </mml:mn></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:mo> − </mml:mo><mml:mrow><mml:mrow><mml:mn> 2 </mml:mn><mml:mover accent="true"><mml:mi> E </mml:mi><mml:mo> ¯ </mml:mo></mml:mover></mml:mrow><mml:mo> / </mml:mo><mml:mrow><mml:msub><mml:mi> τ </mml:mi><mml:mi> G </mml:mi></mml:msub></mml:mrow></mml:mrow><mml:mo> ≈ </mml:mo><mml:mo> − </mml:mo><mml:mn> 2 </mml:mn><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mn> 3 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mn> 35 </mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mo> ) </mml:mo></mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mo> − </mml:mo><mml:mn> 38 </mml:mn></mml:mrow><mml:mo> ) </mml:mo></mml:mrow><mml:mo> = </mml:mo><mml:mn> 2.3 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mn> 37 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> W </mml:mtext></mml:mrow></mml:math></inline-formula>. If we include general relativistic (GR) effects (frame dragging correction), <inline-formula><mml:math display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> − </mml:mo><mml:mrow><mml:mrow><mml:msub><mml:mi> R </mml:mi><mml:mi> s </mml:mi></mml:msub></mml:mrow><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:msup><mml:mo> ≈ </mml:mo><mml:mn> 60 </mml:mn></mml:mrow></mml:math></inline-formula> , we get,</p>
        <disp-formula id="FD18">
          <label>(18)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>P</mml:mi>
                <mml:mrow>
                  <mml:mn>22</mml:mn>
                </mml:mrow>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mn>60</mml:mn>
              <mml:mo>×</mml:mo>
              <mml:mn>2.3</mml:mn>
              <mml:mo>×</mml:mo>
              <mml:msup>
                <mml:mrow>
                  <mml:mn>10</mml:mn>
                </mml:mrow>
                <mml:mrow>
                  <mml:mn>37</mml:mn>
                </mml:mrow>
              </mml:msup>
              <mml:mo>≈</mml:mo>
              <mml:mn>1.4</mml:mn>
              <mml:mo>×</mml:mo>
              <mml:msup>
                <mml:mrow>
                  <mml:mn>10</mml:mn>
                </mml:mrow>
                <mml:mrow>
                  <mml:mn>39</mml:mn>
                </mml:mrow>
              </mml:msup>
              <mml:mtext>
                 
              </mml:mtext>
              <mml:mtext>W</mml:mtext>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>This is the gravitational wave power for an r-mode with angular degree <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> and azimuthal number <inline-formula><mml:math><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mi> l </mml:mi></mml:mrow></mml:math></inline-formula> .</p>
      </sec>
      <sec id="sec3dot2">
        <title>3.2. Gravitational Wave Strain for R-Modes</title>
        <p>The spacetime is distorted by the passage of GWs, therefore, it is important to measure the strain caused by the wave for studying celestial objects in the universe (gravitational wave astronomy). The gravitational wave strain <italic>h</italic> is given by <inline-formula><mml:math><mml:mrow><mml:mrow><mml:mrow><mml:mi> Δ </mml:mi><mml:mi> L </mml:mi></mml:mrow><mml:mo> / </mml:mo><mml:mi> L </mml:mi></mml:mrow></mml:mrow></mml:math></inline-formula> , where, <italic>L</italic> is the distance between two test masses and ∆<italic>L</italic> is the change in separation <italic>L</italic> caused by the GW. The r-mode oscillations which are known to produce GWs from rapidly rotating, celestial compact objects, has a displacement given by Equation (13). The GW strain has the form<inline-formula><mml:math><mml:mrow><mml:mi> h </mml:mi><mml:mrow><mml:mo> ( </mml:mo><mml:mi> t </mml:mi><mml:mo> ) </mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> that, represents the strain as function of time. However, the strain amplitude <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> h </mml:mi><mml:mn> 0 </mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> is calculated using the quadrupole formula adjusted for r-modes which is given approximately by [<xref ref-type="bibr" rid="B5">5</xref>],</p>
        <disp-formula id="FD19">
          <label>(19)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>h</mml:mi>
                <mml:mn>0</mml:mn>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mi>G</mml:mi>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:msup>
                        <mml:mi>c</mml:mi>
                        <mml:mn>4</mml:mn>
                      </mml:msup>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mrow>
                      <mml:msup>
                        <mml:mi>R</mml:mi>
                        <mml:mn>3</mml:mn>
                      </mml:msup>
                      <mml:mi>M</mml:mi>
                      <mml:msup>
                        <mml:mi>Ω</mml:mi>
                        <mml:mn>2</mml:mn>
                      </mml:msup>
                    </mml:mrow>
                    <mml:mo>/</mml:mo>
                    <mml:mi>d</mml:mi>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:mi>α</mml:mi>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mfrac>
                        <mml:mi>ω</mml:mi>
                        <mml:mi>Ω</mml:mi>
                      </mml:mfrac>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mn>2</mml:mn>
              </mml:msup>
              <mml:msub>
                <mml:mi>J</mml:mi>
                <mml:mrow>
                  <mml:mi>l</mml:mi>
                  <mml:mi>m</mml:mi>
                </mml:mrow>
              </mml:msub>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where, <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> J </mml:mi><mml:mrow><mml:mi> l </mml:mi><mml:mi> m </mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> is a dimensionless angular integral approximately ≈ 1 for the <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> r-mode. General relativity (GR) strain correction is calculated by modifying the r-mode frequencies for space-time curvature. For a Kerr-like object, the inertial-frame frequency is approximated as,</p>
        <disp-formula id="FD20">
          <label>(20)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:mi>ω</mml:mi>
              <mml:mo>≈</mml:mo>
              <mml:mrow>
                <mml:mo>(</mml:mo>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mrow>
                      <mml:mn>2</mml:mn>
                      <mml:mi>m</mml:mi>
                      <mml:mi>Ω</mml:mi>
                    </mml:mrow>
                    <mml:mo>/</mml:mo>
                    <mml:mrow>
                      <mml:mi>γ</mml:mi>
                      <mml:mi>l</mml:mi>
                      <mml:mrow>
                        <mml:mo>(</mml:mo>
                        <mml:mrow>
                          <mml:mi>l</mml:mi>
                          <mml:mo>+</mml:mo>
                          <mml:mn>1</mml:mn>
                        </mml:mrow>
                        <mml:mo>)</mml:mo>
                      </mml:mrow>
                    </mml:mrow>
                  </mml:mrow>
                </mml:mrow>
                <mml:mo>)</mml:mo>
              </mml:mrow>
              <mml:msup>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mo>(</mml:mo>
                    <mml:mrow>
                      <mml:mn>1</mml:mn>
                      <mml:mo>−</mml:mo>
                      <mml:mrow>
                        <mml:mrow>
                          <mml:msub>
                            <mml:mi>R</mml:mi>
                            <mml:mi>s</mml:mi>
                          </mml:msub>
                        </mml:mrow>
                        <mml:mo>/</mml:mo>
                        <mml:mi>R</mml:mi>
                      </mml:mrow>
                    </mml:mrow>
                    <mml:mo>)</mml:mo>
                  </mml:mrow>
                </mml:mrow>
                <mml:mrow>
                  <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>/</mml:mo>
                    <mml:mn>2</mml:mn>
                  </mml:mrow>
                </mml:mrow>
              </mml:msup>
              <mml:mo>+</mml:mo>
              <mml:mi>m</mml:mi>
              <mml:mi>Ω</mml:mi>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>where <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> R </mml:mi><mml:mi> s </mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> is the Schwarzschild radius given by, <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> R </mml:mi><mml:mi> s </mml:mi></mml:msub><mml:mo> = </mml:mo><mml:mrow><mml:mrow><mml:mn> 2 </mml:mn><mml:mi> G </mml:mi><mml:mi> M </mml:mi></mml:mrow><mml:mo> / </mml:mo><mml:mrow><mml:msup><mml:mi> c </mml:mi><mml:mn> 2 </mml:mn></mml:msup></mml:mrow></mml:mrow></mml:mrow></mml:math></inline-formula> . The frequency is reduced while the GW amplitude is enhanced by GR effects due to “frame dragging”, approximately with the factor <inline-formula><mml:math display="inline"><mml:mrow><mml:mo> ~ </mml:mo><mml:msup><mml:mrow><mml:mrow><mml:mo> ( </mml:mo><mml:mrow><mml:mn> 1 </mml:mn><mml:mo> − </mml:mo><mml:mrow><mml:mrow><mml:msub><mml:mi> R </mml:mi><mml:mi> s </mml:mi></mml:msub></mml:mrow><mml:mo> / </mml:mo><mml:mi> R </mml:mi></mml:mrow></mml:mrow><mml:mo> ) </mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> . </p>
        <p>We calculate the strain amplitude for the <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> toroidal r-mode, by substituting in Equation (19), the following values are assigned to our compact model: <inline-formula><mml:math><mml:mrow><mml:mi> ω </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 1887 </mml:mn></mml:mrow></mml:math></inline-formula> rad/s with <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> f </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 300 </mml:mn><mml:mtext>   </mml:mtext><mml:mtext> Hz </mml:mtext></mml:mrow></mml:math></inline-formula> (from <bold>Table 1</bold>), <inline-formula><mml:math><mml:mrow><mml:mi> α </mml:mi><mml:mo> ≈ </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 6 </mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> (mode amplitude depends on r-mode excitation), <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> J </mml:mi><mml:mrow><mml:mi> l </mml:mi><mml:mi> m </mml:mi></mml:mrow></mml:msub><mml:mo> ≈ </mml:mo><mml:mn> 1 </mml:mn></mml:mrow></mml:math></inline-formula> (angular integral for <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> ), <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> c </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 3 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mn> 8 </mml:mn></mml:msup><mml:mrow><mml:mtext> m </mml:mtext><mml:mo> / </mml:mo><mml:mtext> s </mml:mtext></mml:mrow></mml:mrow></mml:math></inline-formula> , <italic>G</italic> (gravitational constant) ≈ 6.67 × 10<sup>−</sup><sup>11</sup> m<sup>3</sup>∙Kg<sup>−</sup><sup>1</sup>∙s<sup>−</sup><sup>2</sup>, estimating the distance d between the antimatter universe and the observer to be of the order of magnitude of the radius of our observable universe which is approximately 46.5 billion light years (4.4 × 10<sup>36</sup> m). After substituting in Equations. (19, 20) we get: <inline-formula><mml:math display="inline"><mml:mrow><mml:mi> ω </mml:mi><mml:mo> ≈ </mml:mo><mml:mn> 1992 </mml:mn></mml:mrow></mml:math></inline-formula> rad/s, <inline-formula><mml:math><mml:mrow><mml:msub><mml:mi> h </mml:mi><mml:mn> 0 </mml:mn></mml:msub><mml:mo> ≈ </mml:mo><mml:mn> 0.4 </mml:mn><mml:mo> × </mml:mo><mml:msup><mml:mrow><mml:mn> 10 </mml:mn></mml:mrow><mml:mrow><mml:mo> − </mml:mo><mml:mn> 31 </mml:mn></mml:mrow></mml:msup><mml:mtext>   </mml:mtext><mml:mtext> m </mml:mtext></mml:mrow></mml:math></inline-formula> , and for the strain amplitude after incorporating GR frame dragging (Lense Thirring effect) correction, we get:</p>
        <disp-formula id="FD21">
          <label>(21)</label>
          <mml:math display="inline">
            <mml:mrow>
              <mml:msub>
                <mml:mi>h</mml:mi>
                <mml:mn>0</mml:mn>
              </mml:msub>
              <mml:mo>≈</mml:mo>
              <mml:mn>0.42</mml:mn>
              <mml:mo>×</mml:mo>
              <mml:msup>
                <mml:mrow>
                  <mml:mn>10</mml:mn>
                </mml:mrow>
                <mml:mrow>
                  <mml:mo>−</mml:mo>
                  <mml:mn>29</mml:mn>
                </mml:mrow>
              </mml:msup>
            </mml:mrow>
          </mml:math>
        </disp-formula>
        <p>This strain amplitude is too weak to be readily observed by any currently operating gravitational wave detector. However, the high sensitivity cryogenic LIGO/ VIRGO detectors or the future planned laser interferometer space antenna (LISA) (e.g. [<xref ref-type="bibr" rid="B20">20</xref>]), could plausibly detect the continuous emitted gravitational waves from the antimatter universe. In addition, this ultra-high precision interferometric detection of GWs, could provide the definitive test for general relativity, and whether it is the only theory of relativity, see the illuminating article [<xref ref-type="bibr" rid="B21">21</xref>].</p>
      </sec>
    </sec>
    <sec id="sec4">
      <title>4. Conclusions</title>
      <p>In this article, we have presented the possibility of gravitational wave radiation from the proposed antimatter-universe [<xref ref-type="bibr" rid="B3">3</xref>]. The radiation is emitted from the anti-hydrogen compact core and its relativistic rotating outer-plasma layer. The radiation resulted from the r-modes instability, which is referred to as (CFS) instabilities [<xref ref-type="bibr" rid="B16">16</xref>], that grows and radiates the angular momentum of the compact core [<xref ref-type="bibr" rid="B5">5</xref>] as gravitational waves. The eigen frequencies of the radiation modes were calculated and given in <bold>Table 1</bold>, where the most prominent toroidal bulk mode for the continuous GW emission [<xref ref-type="bibr" rid="B22">22</xref>][<xref ref-type="bibr" rid="B23">23</xref>] was found to be the <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> mode which is likely detectable by LIGO/ VIRGO detectors. The GW-power emitted from the <inline-formula><mml:math><mml:mrow><mml:mi> l </mml:mi><mml:mo> = </mml:mo><mml:mi> m </mml:mi><mml:mo> = </mml:mo><mml:mn> 2 </mml:mn></mml:mrow></mml:math></inline-formula> r-mode adapted for the rapidly rotating compact core of the anti-universe, with compactness parameter of ≈0.49, was found to be ≈1.4 × 10<sup>39</sup> W. This continuous emitted radiation might cause tiny background space fluctuations that fill our universe and would confirm the existence of the dual anti-universe.</p>
      <p>The GW-strain amplitude is evaluated to be about 0.24 × 10<sup>−</sup><sup>29</sup>, which might be too weak to be observed by currently operated gravitational wave detectors. However, the Laser Interferometer Space Antenna (LISA), having flexible 2.5 million Km length arms, which is expected to be launched in space at the beginning of 2030s [<xref ref-type="bibr" rid="B20">20</xref>], would provide even higher sensitivities and is much more suitable for longer wavelength detection. This will enable measuring space disturbances with longer wavelengths caused by gravitational or anti-gravitational waves and could potentially provide more information about the constant-continuous disturbances in the spacetime fabric from the dual antimatter universe, and further determine the distance between our universe and its dual antimatter counterpart. </p>
    </sec>
    <sec id="sec5">
      <title>Acknowledgements</title>
      <p>I would like to express my deepest appreciation to Dr. Ashraf Abul Seoud at the Physics Department of the Faculty of Science—Cairo University for the invaluable feedback and fruitful discussions during the course of this endeavor.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <title>References</title>
      <ref id="B1">
        <label>1.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Blinnikov, S.I., Dolgov, A.D. and Postnov, K.A. (2015) Antimatter and Antistars in the Universe and in the Galaxy. <italic>Physical</italic><italic>Review</italic><italic>D</italic>, 92, Article ID: 023516. https://doi.org/10.1103/physrevd.92.023516 <pub-id pub-id-type="doi">10.1103/physrevd.92.023516</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1103/physrevd.92.023516">https://doi.org/10.1103/physrevd.92.023516</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Blinnikov, S.I.</string-name>
              <string-name>Dolgov, A.D.</string-name>
              <string-name>Postnov, K.A.</string-name>
            </person-group>
            <year>2015</year>
            <article-title>Antimatter and Antistars in the Universe and in the Galaxy</article-title>
            <source>Physical Review D</source>
            <volume>92</volume>
            <fpage>023516</fpage>
            <elocation-id>ID</elocation-id>
            <pub-id pub-id-type="doi">10.1103/physrevd.92.023516</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B2">
        <label>2.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Cohen, A.G., De Rújula, A. and Glashow, S.L. (1998) A Matter-Antimatter Universe? <italic>The</italic><italic>Astrophysical</italic><italic>Journal</italic>, 495, 539-549. https://doi.org/10.1086/305328 <pub-id pub-id-type="doi">10.1086/305328</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1086/305328">https://doi.org/10.1086/305328</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Cohen, A.G.</string-name>
              <string-name>Glashow, S.L.</string-name>
            </person-group>
            <year>1998</year>
            <article-title>A Matter-Antimatter Universe? The Astrophysical Journal, 495, 539-549</article-title>
            <pub-id pub-id-type="doi">10.1086/305328</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B3">
        <label>3.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">El-Sherbini, T.M. (2025) Electromagnetic Radiation from the Antimatter Universe: A Kerr Metric Approach. <italic>Journal</italic><italic>of</italic><italic>High</italic><italic>Energy</italic><italic>Physics</italic>, <italic>Gravitation</italic><italic>and</italic><italic>Cosmology</italic>, 11, 1352-1363. https://doi.org/10.4236/jhepgc.2025.114084 <pub-id pub-id-type="doi">10.4236/jhepgc.2025.114084</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.4236/jhepgc.2025.114084">https://doi.org/10.4236/jhepgc.2025.114084</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>El-Sherbini, T.M.</string-name>
              <string-name>Physics, G</string-name>
            </person-group>
            <year>2025</year>
            <article-title>Electromagnetic Radiation from the Antimatter Universe: A Kerr Metric Approach</article-title>
            <source>Journal of High Energy Physics</source>
            <volume>11</volume>
            <pub-id pub-id-type="doi">10.4236/jhepgc.2025.114084</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B4">
        <label>4.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">El-Sherbini, T.M. (2024) A Model for a Dual Universe. <italic>Journal</italic><italic>of</italic><italic>High</italic><italic>Energy</italic><italic>Physics</italic>, <italic>Gravitation</italic><italic>and</italic><italic>Cosmology</italic>, 10, 52-66. https://doi.org/10.4236/jhepgc.2024.101005 <pub-id pub-id-type="doi">10.4236/jhepgc.2024.101005</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.4236/jhepgc.2024.101005">https://doi.org/10.4236/jhepgc.2024.101005</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>El-Sherbini, T.M.</string-name>
              <string-name>Physics, G</string-name>
            </person-group>
            <year>2024</year>
            <article-title>A Model for a Dual Universe</article-title>
            <source>Journal of High Energy Physics</source>
            <volume>10</volume>
            <pub-id pub-id-type="doi">10.4236/jhepgc.2024.101005</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B5">
        <label>5.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Owen, B.J., Lindblom, L., Cutler, C., Schutz, B.F., Vecchio, A. and Andersson, N. (1998) Gravitational Waves from Hot Young Rapidly Rotating Neutron Stars. <italic>Physical</italic><italic>Review</italic><italic>D</italic>, 58, Article ID: 084020. https://doi.org/10.1103/physrevd.58.084020 <pub-id pub-id-type="doi">10.1103/physrevd.58.084020</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1103/physrevd.58.084020">https://doi.org/10.1103/physrevd.58.084020</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Owen, B.J.</string-name>
              <string-name>Lindblom, L.</string-name>
              <string-name>Cutler, C.</string-name>
              <string-name>Schutz, B.F.</string-name>
              <string-name>Vecchio, A.</string-name>
              <string-name>Andersson, N.</string-name>
            </person-group>
            <year>1998</year>
            <article-title>Gravitational Waves from Hot Young Rapidly Rotating Neutron Stars</article-title>
            <source>Physical Review D</source>
            <volume>58</volume>
            <fpage>084020</fpage>
            <elocation-id>ID</elocation-id>
            <pub-id pub-id-type="doi">10.1103/physrevd.58.084020</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B6">
        <label>6.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Andersson, N. and Kokkotas, K.D. (2001) The R-Mode Instability in Rotating Neutron Stars. <italic>Inter</italic><italic>national</italic><italic>Journal</italic><italic>of</italic><italic>Modern</italic><italic>Physics</italic><italic>D</italic>, 10, 381-441. https://doi.org/10.1142/s0218271801001062 <pub-id pub-id-type="doi">10.1142/s0218271801001062</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1142/s0218271801001062">https://doi.org/10.1142/s0218271801001062</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Andersson, N.</string-name>
              <string-name>Kokkotas, K.D.</string-name>
            </person-group>
            <year>2001</year>
            <article-title>The R-Mode Instability in Rotating Neutron Stars</article-title>
            <source>International Journal of Modern Physics D</source>
            <volume>10</volume>
            <pub-id pub-id-type="doi">10.1142/s0218271801001062</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B7">
        <label>7.</label>
        <citation-alternatives>
          <mixed-citation publication-type="book">Merzbacher, E. (1998) Quantum Mechanics. 3rd Edition, John Wiley &amp; Sons.</mixed-citation>
          <element-citation publication-type="book">
            <person-group person-group-type="author">
              <string-name>Merzbacher, E.</string-name>
              <string-name>Edition, J</string-name>
            </person-group>
            <year>1998</year>
            <article-title>Quantum Mechanics</article-title>
            <source>3rd Edition</source>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B8">
        <label>8.</label>
        <citation-alternatives>
          <mixed-citation publication-type="web">Christensen-Dalsgaard, J. (2014) Lecture Notes on Steller Oscillations. Institute for Fysik og Astronomi. https://users-phys.au.dk/jcd/oscilnotes/Lecture_Notes_on_Stellar_Oscillations.pdf</mixed-citation>
          <element-citation publication-type="web">
            <person-group person-group-type="author">
              <string-name>Christensen-Dalsgaard, J.</string-name>
            </person-group>
            <year>2014</year>
            <article-title>Lecture Notes on Steller Oscillations</article-title>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B9">
        <label>9.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Sotani, H. (2010) Toroidal Oscillations of a Slowly Rotating Relativistic Star in Tensor-Vector-Scalar Theory. <italic>Physical</italic><italic>Review</italic><italic>D</italic>, 82, Article ID: 124061. https://doi.org/10.1103/physrevd.82.124061 <pub-id pub-id-type="doi">10.1103/physrevd.82.124061</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1103/physrevd.82.124061">https://doi.org/10.1103/physrevd.82.124061</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Sotani, H.</string-name>
            </person-group>
            <year>2010</year>
            <article-title>Toroidal Oscillations of a Slowly Rotating Relativistic Star in Tensor-Vector-Scalar Theory</article-title>
            <source>Physical Review D</source>
            <volume>82</volume>
            <fpage>124061</fpage>
            <elocation-id>ID</elocation-id>
            <pub-id pub-id-type="doi">10.1103/physrevd.82.124061</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B10">
        <label>10.</label>
        <citation-alternatives>
          <mixed-citation publication-type="book">Choudhuri, A.R. (2004) The Physics of Fluids and Plasmas: An Introduction for Astrophysicists. Cambridge University Press.</mixed-citation>
          <element-citation publication-type="book">
            <person-group person-group-type="author">
              <string-name>Choudhuri, A.R.</string-name>
            </person-group>
            <year>2004</year>
            <article-title>The Physics of Fluids and Plasmas: An Introduction for Astrophysicists</article-title>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B11">
        <label>11.</label>
        <citation-alternatives>
          <mixed-citation publication-type="book">Summers, H.P. and Mc Whirter, R.W.P. (1984) Applied Atomic Collision Physics, In: Barnett, C.F. and Harrison, M.F.A., Eds., <italic>Volume</italic> 2: <italic>Plasmas</italic>, Academic Press, New York, p. 52. https://www.semanticscholar.org/paper/Lecture-Notes-on-Stellar-Oscillations-Christensen-Dalsgaard/edce6ad17e3c7308ed54413b813f256a411e3782</mixed-citation>
          <element-citation publication-type="book">
            <person-group person-group-type="author">
              <string-name>Summers, H.P.</string-name>
              <string-name>Whirter, R.W.P.</string-name>
              <string-name>Physics, I</string-name>
              <string-name>Barnett, C.F.</string-name>
              <string-name>Harrison, M.F.A.</string-name>
              <string-name>Plasmas, A</string-name>
              <string-name>Press, N</string-name>
            </person-group>
            <year>1984</year>
            <article-title>Applied Atomic Collision Physics, In: Barnett, C</article-title>
            <source>F. and Harrison</source>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B12">
        <label>12.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Gralla, S.E., Lupsasca, A. and Philippov, A. (2016) Pulsar Magnetospheres: Beyond the Flat Spacetime Dipole. <italic>The</italic><italic>Astrophysical</italic><italic>Journal</italic>, 833, Article 258. https://doi.org/10.3847/1538-4357/833/2/258 <pub-id pub-id-type="doi">10.3847/1538-4357/833/2/258</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.3847/1538-4357/833/2/258">https://doi.org/10.3847/1538-4357/833/2/258</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Gralla, S.E.</string-name>
              <string-name>Lupsasca, A.</string-name>
              <string-name>Philippov, A.</string-name>
            </person-group>
            <year>2016</year>
            <article-title>Pulsar Magnetospheres: Beyond the Flat Spacetime Dipole</article-title>
            <source>The Astrophysical Journal</source>
            <volume>833</volume>
            <elocation-id>258</elocation-id>
            <pub-id pub-id-type="doi">10.3847/1538-4357/833/2/258</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B13">
        <label>13.</label>
        <citation-alternatives>
          <mixed-citation publication-type="other">Philippov, A. and Kramer, M. (2022) Pulsar Magnetospheres and Their Radiation. <italic>Annual</italic><italic>Review</italic><italic>of</italic><italic>Astronomy</italic><italic>and</italic><italic>Astrophysics</italic>, 60, 495-558. https://doi.org/10.1146/annurev-astro-052920-112338 <pub-id pub-id-type="doi">10.1146/annurev-astro-052920-112338</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1146/annurev-astro-052920-112338">https://doi.org/10.1146/annurev-astro-052920-112338</ext-link></mixed-citation>
          <element-citation publication-type="other">
            <person-group person-group-type="author">
              <string-name>Philippov, A.</string-name>
              <string-name>Kramer, M.</string-name>
            </person-group>
            <year>2022</year>
            <article-title>Pulsar Magnetospheres and Their Radiation</article-title>
            <source>Annual Review of Astronomy and Astrophysics</source>
            <volume>60</volume>
            <pub-id pub-id-type="doi">10.1146/annurev-astro-052920-112338</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B14">
        <label>14.</label>
        <citation-alternatives>
          <mixed-citation publication-type="book">Jackson, J. (1975) Classical Electrodynamics. 2nd Edition, John Wiley &amp; Sons.</mixed-citation>
          <element-citation publication-type="book">
            <person-group person-group-type="author">
              <string-name>Jackson, J.</string-name>
              <string-name>Edition, J</string-name>
            </person-group>
            <year>1975</year>
            <article-title>Classical Electrodynamics</article-title>
            <source>2nd Edition</source>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B15">
        <label>15.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Rea, N. and De Grandis, D. (2025) Magnetars. arXiv: 2503.04442.v2.</mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Rea, N.</string-name>
              <string-name>Grandis, D.</string-name>
            </person-group>
            <year>2025</year>
            <article-title>Magnetars</article-title>
            <fpage>2503</fpage>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B16">
        <label>16.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Zink, B., Korobkin, O., Schnetter, E. and Stergioulas, N. (2010) Frequency Band of Thef-Mode Chandrasekhar-Friedman-Schutz Instability. <italic>Physical</italic><italic>Review</italic><italic>D</italic>, 81, Article ID: 084055. https://doi.org/10.1103/physrevd.81.084055 <pub-id pub-id-type="doi">10.1103/physrevd.81.084055</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1103/physrevd.81.084055">https://doi.org/10.1103/physrevd.81.084055</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Zink, B.</string-name>
              <string-name>Korobkin, O.</string-name>
              <string-name>Schnetter, E.</string-name>
              <string-name>Stergioulas, N.</string-name>
            </person-group>
            <year>2010</year>
            <article-title>Frequency Band of Thef-Mode Chandrasekhar-Friedman-Schutz Instability</article-title>
            <source>Physical Review D</source>
            <volume>81</volume>
            <fpage>084055</fpage>
            <elocation-id>ID</elocation-id>
            <pub-id pub-id-type="doi">10.1103/physrevd.81.084055</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B17">
        <label>17.</label>
        <citation-alternatives>
          <mixed-citation publication-type="book">Schutz, B.F. (1990) General Relativity. Cambridge University Press.</mixed-citation>
          <element-citation publication-type="book">
            <person-group person-group-type="author">
              <string-name>Schutz, B.F.</string-name>
            </person-group>
            <year>1990</year>
            <article-title>General Relativity</article-title>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B18">
        <label>18.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Torres-Orjuela, A. (2024) How the Spherical Modes of Gravitational Waves Can Be Detected Despite Only Seeing One Ray. <italic>Classical</italic><italic>and</italic><italic>Quantum</italic><italic>Gravity</italic>, 41, Article ID: 117001. https://doi.org/10.1088/1361-6382/ad41b0 <pub-id pub-id-type="doi">10.1088/1361-6382/ad41b0</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1088/1361-6382/ad41b0">https://doi.org/10.1088/1361-6382/ad41b0</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Torres-Orjuela, A.</string-name>
            </person-group>
            <year>2024</year>
            <article-title>How the Spherical Modes of Gravitational Waves Can Be Detected Despite Only Seeing One Ray</article-title>
            <source>Classical and Quantum Gravity</source>
            <volume>41</volume>
            <fpage>117001</fpage>
            <elocation-id>ID</elocation-id>
            <pub-id pub-id-type="doi">10.1088/1361-6382/ad41b0</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B19">
        <label>19.</label>
        <citation-alternatives>
          <mixed-citation publication-type="other">Lindblom, L., Owen, B.J. and Morsink, S.M. (1998) Gravitational Radiation Instability in Hot Young Neutron Stars. <italic>Physical</italic><italic>Review</italic><italic>Letters</italic>, 80, 4843-4846. https://doi.org/10.1103/physrevlett.80.4843 <pub-id pub-id-type="doi">10.1103/physrevlett.80.4843</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1103/physrevlett.80.4843">https://doi.org/10.1103/physrevlett.80.4843</ext-link></mixed-citation>
          <element-citation publication-type="other">
            <person-group person-group-type="author">
              <string-name>Lindblom, L.</string-name>
              <string-name>Owen, B.J.</string-name>
              <string-name>Morsink, S.M.</string-name>
            </person-group>
            <year>1998</year>
            <article-title>Gravitational Radiation Instability in Hot Young Neutron Stars</article-title>
            <source>Physical Review Letters</source>
            <volume>80</volume>
            <pub-id pub-id-type="doi">10.1103/physrevlett.80.4843</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B20">
        <label>20.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Barausse, E., Berti, E., Hertog, T., <italic>et</italic><italic>al</italic>. (2020) Prospects for Fundamental Physics with LISA. arXiv: 2001.09793.</mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Barausse, E.</string-name>
              <string-name>Berti, E.</string-name>
              <string-name>Hertog, T.</string-name>
            </person-group>
            <year>2020</year>
            <article-title>Prospects for Fundamental Physics with LISA</article-title>
            <fpage>2001</fpage>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B21">
        <label>21.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Corda, C. (2009) Interferometric Detection of Gravitational Waves: The Definitive Test for General Relativity. <italic>Inter</italic><italic>national</italic><italic>Journal</italic><italic>of</italic><italic>Modern</italic><italic>Physics</italic><italic>D</italic>, 18, 2275-2282. https://doi.org/10.1142/s0218271809015904 <pub-id pub-id-type="doi">10.1142/s0218271809015904</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1142/s0218271809015904">https://doi.org/10.1142/s0218271809015904</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Corda, C.</string-name>
            </person-group>
            <year>2009</year>
            <article-title>Interferometric Detection of Gravitational Waves: The Definitive Test for General Relativity</article-title>
            <source>International Journal of Modern Physics D</source>
            <volume>18</volume>
            <pub-id pub-id-type="doi">10.1142/s0218271809015904</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B22">
        <label>22.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Ghosh, S., Pathak, D. and Chatterjee, D. (2023) Relativistic Correction to the R-Mode Frequency in Light of Multimessenger Constraints. <italic>The</italic><italic>Astrophysical</italic><italic>Journal</italic>, 944, Article 53. https://doi.org/10.3847/1538-4357/acb0d3 <pub-id pub-id-type="doi">10.3847/1538-4357/acb0d3</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.3847/1538-4357/acb0d3">https://doi.org/10.3847/1538-4357/acb0d3</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Ghosh, S.</string-name>
              <string-name>Pathak, D.</string-name>
              <string-name>Chatterjee, D.</string-name>
            </person-group>
            <year>2023</year>
            <article-title>Relativistic Correction to the R-Mode Frequency in Light of Multimessenger Constraints</article-title>
            <source>The Astrophysical Journal</source>
            <volume>944</volume>
            <elocation-id>53</elocation-id>
            <pub-id pub-id-type="doi">10.3847/1538-4357/acb0d3</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
      <ref id="B23">
        <label>23.</label>
        <citation-alternatives>
          <mixed-citation publication-type="journal">Covas, P.B., Papa, M.A., Prix, R. and Owen, B.J. (2022) Constraints on R-Modes and Mountains on Millisecond Neutron Stars in Binary Systems. <italic>The</italic><italic>Astrophysical</italic><italic>Journal</italic><italic>Letters</italic>, 929, L19. https://doi.org/10.3847/2041-8213/ac62d7 <pub-id pub-id-type="doi">10.3847/2041-8213/ac62d7</pub-id><ext-link ext-link-type="uri" xlink:href="https://doi.org/10.3847/2041-8213/ac62d7">https://doi.org/10.3847/2041-8213/ac62d7</ext-link></mixed-citation>
          <element-citation publication-type="journal">
            <person-group person-group-type="author">
              <string-name>Covas, P.B.</string-name>
              <string-name>Papa, M.A.</string-name>
              <string-name>Prix, R.</string-name>
              <string-name>Owen, B.J.</string-name>
            </person-group>
            <year>2022</year>
            <article-title>Constraints on R-Modes and Mountains on Millisecond Neutron Stars in Binary Systems</article-title>
            <source>The Astrophysical Journal Letters</source>
            <volume>929</volume>
            <pub-id pub-id-type="doi">10.3847/2041-8213/ac62d7</pub-id>
          </element-citation>
        </citation-alternatives>
      </ref>
    </ref-list>
  </back>
</article>