<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">JMP</journal-id><journal-title-group><journal-title>Journal of Modern Physics</journal-title></journal-title-group><issn pub-type="epub">2153-1196</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/jmp.2024.156035</article-id><article-id pub-id-type="publisher-id">JMP-133242</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Physics&amp;Mathematics</subject></subj-group></article-categories><title-group><article-title>
 
 
  Standard Model Fermion Masses and Charges from Holographic Analysis
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>T.</surname><given-names>R. Mongan</given-names></name><xref ref-type="aff" rid="aff1"><sub>1</sub></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Sausalito, CA, USA</addr-line></aff><pub-date pub-type="epub"><day>17</day><month>05</month><year>2024</year></pub-date><volume>15</volume><issue>06</issue><fpage>796</fpage><lpage>803</lpage><history><date date-type="received"><day>18,</day>	<month>April</month>	<year>2024</year></date><date date-type="rev-recd"><day>19,</day>	<month>May</month>	<year>2024</year>	</date><date date-type="accepted"><day>22,</day>	<month>May</month>	<year>2024</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  The Standard Model of particle physics involves twelve fundamental fermions, treated as point particles, in four charge states. However, the Standard Model does not explain why only three fermions are in each charge state or account for neutrino mass. This holographic analysis treats charged Standard Model fermions as spheres with mass 0.187 g/cm&lt;sup&gt;2&lt;/sup&gt; times their surface area, using the proportionality constant in the holographic relation between mass of the observable universe and event horizon radius. The analysis requires three Standard Model fermions per charge state and relates up quark and down quark masses to electron mass. Holographic analysis specifies electron mass, to six significant figures, in terms of fundamental constants &lt;math display='inline' xmlns='http://www.w3.org/1998/Math/MathML'&gt; &lt;mrow&gt; &lt;mi&gt;&amp;#x03B1;&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;&amp;#x210F;&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;&amp;#x039B;&lt;/mi&gt;&lt;/mrow&gt; &lt;/math&gt; and &lt;math display='inline' xmlns='http://www.w3.org/1998/Math/MathML'&gt; &lt;mrow&gt; &lt;msub&gt; &lt;mi&gt;&amp;#x03A9;&lt;/mi&gt; &lt;mi&gt;&amp;#x039B;&lt;/mi&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;/math&gt;. Treating neutrinos as spheres and equating electron neutrino energy density with cosmic vacuum energy density predicts neutrino masses consistent with experiment.
 
</p></abstract><kwd-group><kwd>Electron Mass</kwd><kwd> Up Quark Mass</kwd><kwd> Down Quark Mass</kwd><kwd> Neutrino Masses</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>This holographic analysis</p><p>1) Explains why three Standard Model fermions are in each charge state e , 2 3 e and − 1 3 e ;</p><p>2) Relates electron mass to up and down quarks masses;</p><p>3) Specifies electron mass in terms of fine structure constant α, Planck’s constant ℏ , gravitational constant G, cosmological constant Λ, and vacuum energy fraction Ω Λ .</p></sec><sec id="s2"><title>2. Background for Holographic Analysis</title><p>Holographic analysis is based on quantum mechanics, general relativity, thermodynamics, and Shannon information theory. Bousso’s [<xref ref-type="bibr" rid="scirp.133242-ref1">1</xref>] review of holographic analysis indicates only about 5 &#215; 10<sup>122</sup> of bits of information on the event horizon will ever be available to describe physics in our universe where the cosmological constant [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] is Λ = 1.088 &#215; 10 − 56   cm 2 .</p><p>The radius of the event horizon is R H = 3 / Λ = 1.66 &#215; 10 28   cm . With Hubble constant [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] H 0 = 67.4   km / ( sec ⋅ Mpc ) , critical energy density ρ c r i t = 3 H 0 2 8 π G , gravitational constant [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] G = 6.67430 &#215; 10 − 8 cm 3 / ( g ⋅ sec 2 ) , and vacuum energy fraction [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] Ω Λ = 0.685 , the mass of the observable universe within the event horizon is M H = 4 3 π ( 1 − Ω Λ ) ρ c r i t R H 3 = ( 0.187   g / cm 2 ) R H 2 . So M H is the total mass of the bits of information necessary to describe all physics within the event horizon, indicating the bits of information describing a particle with definite mass m within the universe are available on a spherical surface around the particle with radius r = m M H R H .</p></sec><sec id="s3"><title>3. Input Data</title><p>Discussion of charged Standard Model fermion masses must begin with PDG [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] 2023 experimental data on those masses. PDG [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] 2023 lists electron mass m e = 0.511   MeV / c 2 = 9.11 &#215; 10 − 28   g , up quark mass m u p = 2.16 − .26 + .49   MeV / c 2 , and down quark mass m d o w n = 4.67 − .26 + .49   MeV / c 2 where c is the speed of light. Up and down quark holographic radii r u p = 2 r e , r d o w n = 3 r e and quark masses m u p = 4 m e , m d o w n = 9 m e used in this analysis are consistent with PDG data. <xref ref-type="table" rid="table1">Table 1</xref> then lists masses and holographic radii of the nine charged Standard Model fermions as used in this analysis.</p><table-wrap id="table1" ><label><xref ref-type="table" rid="table1">Table 1</xref></label><caption><title> Charged standard model fermion masses and holographic radii</title></caption><table><tbody><thead><tr><th align="center" valign="middle" >Fermion</th><th align="center" valign="middle" >Charge</th><th align="center" valign="middle" >Mass (MeV/c<sup>2</sup>)</th><th align="center" valign="middle" >Holographic radius r (fm)</th></tr></thead><tr><td align="center" valign="middle" >electron</td><td align="center" valign="middle" >−e</td><td align="center" valign="middle" >0.510999</td><td align="center" valign="middle" >0.698031</td></tr><tr><td align="center" valign="middle" >muon</td><td align="center" valign="middle" >−e</td><td align="center" valign="middle" >105.7</td><td align="center" valign="middle" >10.04</td></tr><tr><td align="center" valign="middle" >tau</td><td align="center" valign="middle" >−e</td><td align="center" valign="middle" >1777</td><td align="center" valign="middle" >41.16</td></tr><tr><td align="center" valign="middle" >up quark</td><td align="center" valign="middle" >2e/3</td><td align="center" valign="middle" >2.04340</td><td align="center" valign="middle" >1.39606</td></tr><tr><td align="center" valign="middle" >charm quark</td><td align="center" valign="middle" >2e/3</td><td align="center" valign="middle" >1270</td><td align="center" valign="middle" >34.80</td></tr><tr><td align="center" valign="middle" >top quark</td><td align="center" valign="middle" >2e/3</td><td align="center" valign="middle" >173,000</td><td align="center" valign="middle" >406</td></tr><tr><td align="center" valign="middle" >down quark</td><td align="center" valign="middle" >−e/3</td><td align="center" valign="middle" >4.59899</td><td align="center" valign="middle" >2.09409</td></tr><tr><td align="center" valign="middle" >strange quark</td><td align="center" valign="middle" >−e/3</td><td align="center" valign="middle" >93.4</td><td align="center" valign="middle" >9.44</td></tr><tr><td align="center" valign="middle" >bottom quark</td><td align="center" valign="middle" >−e/3</td><td align="center" valign="middle" >4180</td><td align="center" valign="middle" >6.31</td></tr></tbody></table></table-wrap></sec><sec id="s4"><title>4. Charged Standard Model Fermion Structure and Masses</title><p>Standard Model fermions described as spheres with holographic radius r, mass m = ( 0.187   g / cm 2 ) r 2 , and matter density ρ = m / ( 4 3 π r 3 ) have a surface mass component and an axial mass component along their rotation axis. Holographic analysis is based in part on general relativity, and general relativity is not valid at distances less than the Planck length</p><p>l P = ℏ G c 3 = 1.61625 &#215; 10 − 33   cm = 1.61625 &#215; 10 − 20   fm , so fermion surface mass components are treated as spherical shells with mass m S , thickness l P , and matter density ρ S l P per unit area, while axial mass components with mass m A are treated as cylinders with diameter l P and matter density ρ A l P 2 per unit length. A cubic equation for fermion holographic radius in each charge state is</p><p>4 3 π ρ r 3 = m S + m A = ρ S l P 4 π r 2 + ρ A π l P 2 ( 2 r )</p><p>or</p><p>ρ r 3 − 3 ρ S l P r 2 − 3 2 ρ A l P 2 r = a r 3 + b r 2 + c r = 0</p><p>with a = ρ , b = − 3 ρ S l P and c = − 3 2 ρ A l P 2 . Discriminant b 2 c 2 − 4 a c 3 of the cubic is positive and three real roots of the equation correspond to holographic radii of three fermions per charge state. Parameters ρ S and ρ A (determined by holographic radii r<sub>1</sub>, r<sub>2</sub>, and r<sub>3</sub>) using Nickalls’ solutions [<xref ref-type="bibr" rid="scirp.133242-ref3">3</xref>] to cubic equations involving</p><p>r N = r 1 + r 2 + r 3 3 and δ 2 = ( r 1 − r N ) 2 4 + ( r 2 − r 3 ) 2 12</p><p>are ρ S l P = r N ρ , from r N = − b / 3 , and ρ A l P 2 = 2 ρ ( r N 2 − δ 2 ) , from δ 2 = b 2 − 3 a c 9 a 2 .</p><p>Tangential velocity v T of points on fermion surfaces are found from I ω = ℏ / 2 , where fermion moment of inertia I = I S + I A , with shell moment of inertia I S = 2 3 m S r 2 , axial moment of inertia I A = m A 2 ( l P 2 ) 2 , and I S ≫ I A . The electron is the only Standard Model fermion with v T = ℏ 4 m r N &gt; c , but points on the electron surface are not particles and cannot send signals, so no particle or signal travels with speed &gt;c.</p></sec><sec id="s5"><title>5. Electron, Up Quark, and Down Quark Masses</title><p>All persistent structures in the universe are composed of electrons, protons, and neutrons. Protons and neutrons are composed of up and down quarks. So the lowest mass Standard Model fermions in each charge state (electrons, up quarks, and down quarks) are constituents of all persistent structures in the universe. Holographic analysis then provides succinct explanations relating lowest mass Standard Model fermions in each charge state.</p><p>Electrons, the only Standard Model fermions that can persist in isolation in the universe, have the smallest mass and holographic radius of the nine charged Standard Model fermions. Up quarks, with twice the electron holographic radius, have four times the electron mass. Down quarks, with three times the electron holographic radius, have nine times the electron holographic mass.</p><p>Protons are composed of two up quarks and one down quark, and neutrons are composed of two down quarks and one up quark. Isolated neutrons decay to protons, so up quarks must have lower mass than down quarks, consistent with experimental data.</p></sec><sec id="s6"><title>6. Electron Mass from α , ℏ , G , Λ and Ω Λ</title><p>Using electron holographic radius r e = m e M H R H , holographic analysis specifies electron mass to six significant figures in terms of fundamental constants α , ℏ , G , Λ and Ω Λ .</p><p>Our universe is so large it is almost flat, and Friedmann’s equation H 0 2 = 8 π G 3 ρ c r i t + Λ c 2 3 identifies Ω Λ = Λ c 2 3 H 0 2 . Since M H = 4 3 π ( 1 − Ω Λ ) ρ c r i t R H 3 , M H = ( 1 − Ω Λ ) c 2 2 G Ω Λ 3 Λ is constant in time.</p><p>Electrostatic potential energy of electron charge e and positron charge −e separated by 2 r e is V = − e 2 2 r e = − α ℏ c 2 r e , with Planck’s constant [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] ℏ = 1.05457 &#215; 10 − 27 g ⋅ cm 2 / sec . Adjacent spheres with holographic radii r e , a precursor for electron-positron pair production, have total energy E = 2 m e c 2 − α ℏ c 2 r e = 0 when r e = α ℏ c 4 m e c 2 .</p><p>Two equations for r e give α ℏ c 4 m e c 2 = m e M H R H and electron mass m e = [ ( α ℏ 2 32 ) ( 1 − Ω Λ G Ω Λ Λ 3 ) ] 1 / 3 .</p><p>If Λ = 1.08800 &#215; 10 − 56   cm 2 and Ω Λ = 0.6853855 (within PDG [<xref ref-type="bibr" rid="scirp.133242-ref2">2</xref>] 2023 error bars) electron mass is specified to six significant figures, since gravitational constant G is only known to six significant figures.</p></sec><sec id="s7"><title>7. Neutrino Masses</title><p>Each lepton has a corresponding neutrino, but neutrinos oscillate between mass states when propagating through space and are not persistent structures in the universe. So neutrinos are not consistently related to holographic radii. Characteristic lengths of neutrinos are Compton wavelengths λ = ℏ m c . Electron neutrinos with radius 1 4 ℏ m c and the lowest energy density in the universe (cosmic vacuum energy density ρ v = 5.83 &#215; 10 − 30 g / cm 3 ) have mass m 1 = [ π 6 ρ v ( ℏ c ) 3 ] 1 4 = 2.02 &#215; 10 − 36   g = 0.0013   eV . Neutrino oscillation data [<xref ref-type="bibr" rid="scirp.133242-ref4">4</xref>] predict m 2 = m 1 2 + 7.37 &#215; 10 − 5   eV 2 = 0.00866   eV and m 3 = 0.5 ( m 1 + m 2 ) 2 + 2.5 &#215; 10 − 3   eV 2 = 0.0505   eV . Neutrino mass sum 0.0603 eV is then 50% of Vagnozzi’s [<xref ref-type="bibr" rid="scirp.133242-ref5">5</xref>] experimental upper limit of 0.12 eV on neutrino mass sum.</p></sec><sec id="s8"><title>8. Results</title><p>This holographic analysis based on quantum mechanics, general relativity, thermodynamics, and Shannon information theory:</p><p>1) Requires three Standard Model fermions in each charge state e , 2 3 e , and − 1 3 e ;</p><p>2) Relates masses of the electron, up quark, and down quark constituents of all permanent structures in the universe to electron mass;</p><p>3) Specifies electron mass in terms of fundamental constants α , ℏ , G , Λ and Ω Λ ;</p><p>4) Accounts for observed matter dominance in the universe, if the universe is closed.</p></sec><sec id="s9"><title>9. Conclusion</title><p>This analysis, specifying electron, up quark, down quark, and three neutrino masses, reduces by six the number of free parameters in the Standard Model of particle physics. These results can provide insight to develop physical theories to supplement the Standard Model.</p></sec><sec id="s10"><title>Conflicts of Interest</title><p>The author declares no conflicts of interest regarding the publication of this paper.</p></sec><sec id="s11"><title>Cite this paper</title><p>Mongan, T.R. (2024) Standard Model Fermion Masses and Charges from Holographic Analysis. Journal of Modern Physics, 15, 796-803. https://doi.org/10.4236/jmp.2024.156035</p></sec><sec id="s12"><title>Appendix: Matter Dominance in a Closed Universe</title><p>Charged bits on Standard Model fermion surfaces must be at the rotation axis, to avoid radiation from accelerated charge. Bits of information on the horizon can indicate presence of a charged Standard Model fermion somewhere along the axis between diametrically opposed bits of information on opposite hemispheres of the horizon, so charge &#177;e/6 must be associated with each bit of information. One, two, or three bit pairs on opposite surfaces of spherical Standard Model fermions at their rotation axis specify charge −e/3 or 2e/3 quarks, or charge e leptons.</p><p>A closed universe beginning by a quantum fluctuation from nothing [<xref ref-type="bibr" rid="scirp.133242-ref6">6</xref>] must be charge neutral, with equal numbers of e/6 and −e/6 bits. Regardless of details of how bits of information specify protons or anti-protons, configurations specifying protons differ in 6 bits from configurations specifying anti-protons. In any physical system, energy is transferred to change bits from one state to another, and e/6 bits with lower energy than −e/6 bits result in more matter than anti-matter in a closed universe, as discussed below.</p><p>Temperature at time of baryon formation was T B = 2 m p c 2 k = 2.18 &#215; 10 3   K , with</p><p>Boltzmann constant k = 1.38 &#215; 10 − 16 ( g ⋅ cm 2 / sec 2 ) / K and proton mass m p = 1.67 &#215; 10 − 24   g . Radius of the universe at baryogenesis was [<xref ref-type="bibr" rid="scirp.133242-ref7">7</xref>]</p><p>R B = ( 2.725 2.18 &#215; 10 3 ) R 0 ≈ 10 15   cm , where 2.725 K is today’s microwave background</p><p>temperature and radius of the universe today is R 0 ≈ 10 28   cm . Baryogenesis time t B in seconds after the end of inflation is determined by Friedmann’s equation</p><p>( d R d t ) 2 − ( 8 π G 3 ) ε ( R ) ( R c ) 2 = − κ c 2 . After inflation, in a closed universe so large</p><p>it is almost flat, curvature parameter κ ≈ 0 . Energy density</p><p>ε ( R ) = ε r ( R 0 R ) 4 + ε m ( R 0 R ) 3 + ε v , where ε r , ε m and ε v are today’s radiation,</p><p>matter, and vacuum energy densities. Matter energy density</p><p>ε m ≈ 9 &#215; 10 − 9 ( g ⋅ cm 2 ⋅ sec − 2 / cm 3 ) , and vacuum energy density was negligible in the early universe, so radiation dominated when R ≪ 10 − 5 R 0 before radiation/</p><p>matter equality. Integrating ( d R d t ) 2 − ( 8 π G 3 c 2 ) ε r R 0 4 R 2 = ( d R d t ) 2 − A 2 R 2 = 0 where A = 8 π G ε r R 0 4 3 c 2 , from the end of inflation at t = 0 to t, determines A t = 1 2 ( R ( t ) 2 − R i 2 ) , where R i is radius of the universe at the end of inflation and R B ≫ R i . So t B = R B 2 − R i 2 2 A ≈ R B 2 2 A ≈ 10 − 7 seconds. Distance from any point in the universe at baryogenesis to the horizon for that point [<xref ref-type="bibr" rid="scirp.133242-ref8">8</xref>] is d B = c ∫ 0 t B d t ′ R ( t ′ ) = c R B A [ R i 2 + 2 A t B − R i ] ≈ c R B 2 A ≈ 10 4   cm .</p><p>Surface gravity on the horizon at baryogenesis is</p><p>g H B = G 4 π 3 ε ( R B ) c 2 d B ≈ 4 π G 3 c ε r R 0 4 A R B 2 , and associated horizon temperature [<xref ref-type="bibr" rid="scirp.133242-ref9">9</xref>] is T H B = ℏ 2 π c k g H B ≈ 6 &#215; 10 − 7   K . Occupation probabilities of bits on the horizon at</p><p>baryogenesis are proportional to their Boltzmann factors. If energy of e/6 bits is E − Δ and energy of −e/6 bits is E + Δ , proton-antiproton ratio at baryogenesis</p><p>is ( e − E − Δ k T H B / e − E + Δ k T H B ) 6 = e 12 Δ k T H B ≈ 1 + 12 Δ k T H B and proton excess is 12 Δ k T H B . Energy released when a −e/6 bit on the horizon changes to an e/6 bit raises another bit from e/6 to −e/6, ensuring charge conservation. Energy to change the state of bits on the horizon must be transferred by massless quanta with wavelength related to the scale of the horizon, and the only macroscopic length characteristic of the horizon at baryogenesis is the circumference 2 π R B . If energy 2Δ to change the state of bits on the horizon (and corresponding bits within the universe) is energy of massless quanta with wavelength characteristic of a closed Friedmann universe with radius R B at baryogenesis, 2 Δ = ℏ c R B . Substituting from above, proton excess at baryogenesis is 12 Δ k T H B = ( 24 π c 2 R 0 ) ( 2.725 T B ) 3 8 π G ε r ≈ 1.8 &#215; 10 − 9 .</p><p>WMAP [<xref ref-type="bibr" rid="scirp.133242-ref10">10</xref>] found (baryon density)/(microwave background photon density) = 6.1 &#215; 10<sup>−10</sup>. At baryogenesis, the number of protons, anti-protons, and photons were approximately equal. When almost all protons and anti-protons annihilated to two photons, the baryon to photon ratio became 1 3 ( 1.8 &#215; 10 − 9 ) = 6 &#215; 10 − 10 , in agreement with WMAP results.</p></sec></body><back><ref-list><title>References</title><ref id="scirp.133242-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">Bousso, R. (2002) &lt;i&gt;Reviews of Modern Physics&lt;/i&gt;, 74, 825.&lt;br&gt;https://doi.org/10.1103/RevModPhys.74.825 </mixed-citation></ref><ref id="scirp.133242-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">Workman, R., &lt;i&gt;et al&lt;/i&gt;&lt;i&gt;.&lt;/i&gt;&lt;i&gt; &lt;/i&gt;[Particle Data Group] (2022) Reviews, Tables &amp; Plots. &lt;br&gt;https://www.pdg.lbl.gov/2023/listings/contents_listings.html </mixed-citation></ref><ref id="scirp.133242-ref3"><label>3</label><mixed-citation publication-type="other" xlink:type="simple">Nickalls, R. (1993) &lt;i&gt;The Mathematical Gazette&lt;/i&gt;, 77, 354-359. &lt;br&gt;https://doi.org/10.2307/3619777</mixed-citation></ref><ref id="scirp.133242-ref4"><label>4</label><mixed-citation publication-type="other" xlink:type="simple">Capozzi, F., Lisi, E., Marrone, A., Montanino, D. and Palazzo, A. (2016) &lt;i&gt;Nuclear Physics B&lt;/i&gt;, 908, 218-234. &lt;br&gt;https://doi.org/10.1016/j.nuclphysb.2016.02.016</mixed-citation></ref><ref id="scirp.133242-ref5"><label>5</label><mixed-citation publication-type="other" xlink:type="simple">Vagnozzi, S. (2019) Cosmological Searches for the Neutrino Mass Scale and Mass Ordering. Ph.D. Thesis, Stockholm University, Stockholm.</mixed-citation></ref><ref id="scirp.133242-ref6"><label>6</label><mixed-citation publication-type="other" xlink:type="simple">Mongan, T. (2001) &lt;i&gt;General Relativity and Gravitation&lt;/i&gt;, 33, 1415-1424. &lt;br&gt;https://doi.org/10.1023/A:1012065826750</mixed-citation></ref><ref id="scirp.133242-ref7"><label>7</label><mixed-citation publication-type="other" xlink:type="simple">Dodelson, S. (2003) Modern Cosmology. Academic Press, San Diego, 4.</mixed-citation></ref><ref id="scirp.133242-ref8"><label>8</label><mixed-citation publication-type="other" xlink:type="simple">Islam, J. (2002) An Introduction to Mathematical Cosmology. 2nd Edition, Cambridge University Press, Cambridge, 73.</mixed-citation></ref><ref id="scirp.133242-ref9"><label>9</label><mixed-citation publication-type="other" xlink:type="simple">Padmanabhan, T. (2010) A Physical Interpretation of Gravitational Field Equations. &lt;i&gt;AIP Conference Proceedings&lt;/i&gt;, 1241, 93-108. &lt;br&gt;https://doi.org/10.1063/1.3462738</mixed-citation></ref><ref id="scirp.133242-ref10"><label>10</label><mixed-citation publication-type="other" xlink:type="simple">Bennet, C., &lt;i&gt;et al&lt;/i&gt;. (2003) &lt;i&gt;The Astrophysical Journal Supplement Series&lt;/i&gt;, 148, 1-27.</mixed-citation></ref></ref-list></back></article>