<?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.2012.39120</article-id><article-id pub-id-type="publisher-id">JMP-22613</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>
 
 
  Algebras of Hamieh and Abbas Used in the Dirac Equation
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>regory</surname><given-names>Peter Wene</given-names></name><xref ref-type="aff" rid="aff1"><sub>1</sub></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Department of Mathematics, The University of Texas at San Antonio, San Antonio, USA</addr-line></aff><author-notes><corresp id="cor1">* E-mail:<email>gwene@utsa.edu</email></corresp></author-notes><pub-date pub-type="epub"><day>24</day><month>09</month><year>2012</year></pub-date><volume>03</volume><issue>09</issue><fpage>923</fpage><lpage>926</lpage><history><date date-type="received"><day>June</day>	<month>16,</month>	<year>2012</year></date><date date-type="rev-recd"><day>July</day>	<month>26,</month>	<year>2012</year>	</date><date date-type="accepted"><day>August</day>	<month>3,</month>	<year>2012</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>
 
 
  Hamieh and Abbas [1] propose using a 3-dimensional real algebra in a solution of the Dirac equation. We show that this algebra, denoted by , belongs to a large class of quadratic Jordan algebras with subalgebras isomorphic to the complex numbers and that the spinor matrices associated with the solution of the Dirac equation generate a six-dimensional real noncommutative Jordan algebra.
 
</p></abstract><kwd-group><kwd>Dirac Equation; Jordan Algebra; Quadratic Algebra</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>Let <img src="5-7500717\3dd00c0c-d6a5-4913-b531-65731e4195f2.jpg" /> be an algebra over a field F not of characteristic two. The associator is a trilinear mapping</p><p><img src="5-7500717\44456e06-a926-473b-aec1-c2d5f57b469e.jpg" /></p><p>of <img src="5-7500717\4136fb4e-5435-40ee-b3a5-21257af431ea.jpg" /> into <img src="5-7500717\ca9e75d6-be57-474d-9af1-c3d5787e38fc.jpg" /> that measures the lack of associativity in<img src="5-7500717\6906becd-75c7-457d-9a0b-ff83ecd476b0.jpg" />.</p><p>One scheme of classifying nonassociative algebras involves placing conditions on the associator of certain sets of elements. Some of the better known algebras are:</p><p>1) Alternative algebras. In this variety of algebras, all elements x and y satisfy</p><p><img src="5-7500717\7523f0ab-12c4-4d0f-92a8-443d754f23e8.jpg" /></p><p>for all elements x and y. The octonion division ring is an alternative algebra. An interesting variation is psuedooctonion algebra (Okubo [5,9]).</p><p>2) Jordan algebras. These are commutative algebras in which all x and y satisfy</p><p><img src="5-7500717\c1185bc0-9d89-45fb-af76-1544d6aecab7.jpg" /></p><p>A Type D Jordan algebra is the Jordan algebra of the symmetric bilinear form q on a vector space<img src="5-7500717\7b080f65-befd-4fdd-a1ba-7ee230264933.jpg" />. Albert [<xref ref-type="bibr" rid="scirp.22613-ref3">3</xref>] has shown that any algebra of Type D has a basis <img src="5-7500717\65e3eeeb-954e-46a3-bb7d-22f31934f31b.jpg" /> with multiplication given by</p><p><img src="5-7500717\2d9f8ce7-77fa-42e8-953a-d2aff56f5654.jpg" /></p><p><img src="5-7500717\cd262f25-54fe-449e-b7fa-1e98bd428023.jpg" /></p><p>The algebra will be semisimple if <img src="5-7500717\df711898-9584-4f1f-85ee-8b5fe1bfd5e3.jpg" /> for all<img src="5-7500717\8132c5f4-cb92-4c6f-ab4e-2b4d19cccd27.jpg" />.</p><p>3) Noncommutative Jordan algebras. A generalization of the alternative and Jordan algebras that requires all x and y satisfy a generalization of the commutative law</p><p><img src="5-7500717\02ce1ed3-7db9-44a6-80a9-9305ad630cf3.jpg" /></p><p>that is, the algebras are flexible, and</p><p><img src="5-7500717\35ccb197-d215-4ade-a065-d845ef6639a1.jpg" /></p><p>The book by Zhevlakov, Slin’ko, Shestakov and Shirshov [<xref ref-type="bibr" rid="scirp.22613-ref10">10</xref>] provides a detailed analysis of the alternative and Jordan rings.</p><p>The above algebras are all power associative since each element a generates an associative subalgebra; equivalently, <img src="5-7500717\e84a39c2-013a-49b5-a496-0b00856618f3.jpg" />for positive integers<img src="5-7500717\5069b40b-f400-4e75-9042-b77b8399c0a8.jpg" />. In any power associative algebra <img src="5-7500717\a7506d83-8800-40a2-950a-2dd791315a0b.jpg" /> with unit element we can introduce the series</p><p><img src="5-7500717\076ff8f0-16c5-4498-b535-2e502e01db3e.jpg" /></p><p>for <img src="5-7500717\d0f4d9ca-5918-47f8-9a18-fa19a1e0f64d.jpg" /> ignoring the question of convergence.</p><p>An algebra <img src="5-7500717\39639aeb-47e6-48db-90f3-fa4aa90cb1ed.jpg" /> over a field F is called quadratic if, for every x in <img src="5-7500717\cc3d6e30-5262-406e-a27c-cbd86f4d53ff.jpg" /></p><p><img src="5-7500717\d9a8430a-b23c-49cd-b86e-9b9d5a33091a.jpg" /></p><p>where <img src="5-7500717\b5dd1385-5734-4da1-b577-384fb639cac2.jpg" /> are in F and e is the identity of<img src="5-7500717\e2d51c04-6d71-4e7f-ad92-46269517e361.jpg" />. The quantities <img src="5-7500717\39a4a6d8-85fb-4ba0-9af2-53f7172a4ae6.jpg" /> and <img src="5-7500717\f49ab9ad-5747-413c-86c4-369c5bb01e42.jpg" /> are called the trace and norm of the element x, respectively. The trace is a linear functional on <img src="5-7500717\58641c0d-3836-4623-8c08-1cc829db7fd9.jpg" /> see Schafer [<xref ref-type="bibr" rid="scirp.22613-ref7">7</xref>]. The norm <img src="5-7500717\0ba0b43c-3e87-45c3-99d6-ff7af9d0795f.jpg" /> defines a symmetric bilinear form <img src="5-7500717\be74619e-f01a-49c4-9e48-94c47f6d9b63.jpg" /> on <img src="5-7500717\75d3ae47-604c-4bee-8a54-997f85321c47.jpg" /> via</p><p><img src="5-7500717\2f16e001-8997-4cc3-b8e7-4d3c2e349d8e.jpg" /></p><p>Say <img src="5-7500717\3febe827-03e8-4276-afc9-af08b3f1ab9e.jpg" /> is nondegenerate if <img src="5-7500717\96838636-2155-49a5-8472-e1c9ea2846ad.jpg" /> is. Any quadratic algebra is power associative and any flexible, quadratic algebra is a noncommutative Jordan algebra.</p><p>A quadratic algebra <img src="5-7500717\c4db3a4b-11ae-4d87-8788-ffe42d1dcf3b.jpg" /> is flexible if and only if the trace is associative; that is, <img src="5-7500717\f5ada10d-5aa8-423b-b05d-e718fbbe5198.jpg" />for all <img src="5-7500717\6e9f1dfa-a211-4fef-9f33-4d6f96999525.jpg" /> in<img src="5-7500717\d3c08e94-5ada-487b-95f2-d4213248bb6c.jpg" />. If <img src="5-7500717\86bf1214-9dca-410a-8948-8428563ae387.jpg" /> is flexible then the mapping <img src="5-7500717\cb472556-b961-469a-9808-1ec71cd792cf.jpg" /> is an involution in <img src="5-7500717\4ed60ad9-267e-4889-a033-be5562c15fa4.jpg" /> (see Braun and Koecher [<xref ref-type="bibr" rid="scirp.22613-ref11">11</xref>], p. 216).</p><p>Lemma 1. The Hamiltonian division ring is a quadratic algebra.</p><p>Proof. Let <img src="5-7500717\91679e2e-4e80-4520-ac43-46625679d20f.jpg" /> be an element of the Hamitonian division ring. Direct computation shows that</p><p><img src="5-7500717\b5f969ba-2396-474c-9a9a-1913efff2cfe.jpg" />.</p><p>Example 1. The octonion division ring is a quadratic algebras.</p><p>Example 2. Domokos and K&#246;vesi-Domokos [<xref ref-type="bibr" rid="scirp.22613-ref12">12</xref>] propose a quadratic algebra, the “algebra of color” as a candidate for the algebra obeyed by a quantized field describing quarks and leptons (see also Wene [13,14], and Schafer [<xref ref-type="bibr" rid="scirp.22613-ref15">15</xref>]).</p></sec><sec id="s2"><title>2. Construction of the Algebras</title><p>The elements of the algebra <img src="5-7500717\769ddaf1-ab28-4592-9f65-3ba8724073a6.jpg" /> are the elements of the real vector space with basis<img src="5-7500717\77e404f3-ca08-413a-ba74-8d3ce0e8d555.jpg" />. The addition is the vector space addition and multiplication is defined by<img src="5-7500717\97b64950-9f02-4bf4-b1d4-ac73cfcb31d8.jpg" />, <img src="5-7500717\88a65c3b-8470-4522-97b3-2643b85edc10.jpg" />, <img src="5-7500717\9aba27bb-21a3-4f70-ae0a-0f270b116154.jpg" />is the identity and the distributive laws. We note that the algebra is commutative and has divisors of zero.</p><p>An immediate generalization of this algebra has a basis<img src="5-7500717\02b3c4bd-3ccc-4ce9-8a77-3b28b922e26c.jpg" />, <img src="5-7500717\c5e69867-d52f-4569-94a1-9cf3eb0666ba.jpg" />over the field <img src="5-7500717\98ff42b8-937a-4f06-8358-34c5790396cc.jpg" /> of real numbers and multiplication defined by <img src="5-7500717\02f2ab0c-d5f5-4b7d-8047-abe1be6f76b8.jpg" /> where <img src="5-7500717\dc088bf9-74f1-4001-b790-6d6f6bb0f31f.jpg" /> is the identity. For want of a better name called these the Abbas algebras. As noted above, these algebras are Type D Jordan algebras. Note that the <img src="5-7500717\414ab11f-4afa-4ba1-8c20-028e08b9d6ef.jpg" /> algebra is the construction for<img src="5-7500717\6c0ee8e3-f228-4757-84eb-67a408adb612.jpg" />; the results for the Abbas algebras apply to the<img src="5-7500717\3e6707a2-3e6a-419c-acd3-c2a36e5d85b9.jpg" />. Each Abbas algebra contains a copy of the complex numbers.</p><p>Lemma 2. The Abbas algebras are quadratic algebras.</p><p>Proof. Let H denote a Abbas algebra. Then if<img src="5-7500717\c4c30cca-14ad-47bf-b147-d6e82df12d53.jpg" />, <img src="5-7500717\9f88f86f-9614-4c56-b391-b1e95f859893.jpg" />, Einstein summation convention where <img src="5-7500717\b0d80bc6-941d-42fc-aa97-d2a16837d140.jpg" /> Then</p><p><img src="5-7500717\1e929fb9-273f-4459-91e9-de704d625f60.jpg" /></p><p><img src="5-7500717\cbd564a5-aaf8-468b-b982-fbb7e6c5dc70.jpg" /></p><p>Adding both sides gives</p><p><img src="5-7500717\cc10f7f9-d4df-4d55-87f6-a12b21289609.jpg" /></p><p>and we see that <img src="5-7500717\c4880dff-2269-479c-971d-9c341620e054.jpg" /> and<img src="5-7500717\dc565f00-d82f-4e4f-9dfb-488442db3194.jpg" />.</p><p>A commutative quadratic algebra will be a Jordan algebra.</p><p>Since the algebra is commutative the trace is associative; the norm is symmetric.</p><p>Lemma 3. The norm of a Abbas algebra is nondegenerate.</p><p>Proof. Let H denote a Abbas algebra. Then if<img src="5-7500717\65f24eaa-202f-439c-9e25-1c7793c887e8.jpg" />, <img src="5-7500717\7e3d5c8f-86c1-4bb8-ad8c-66ed40c1d63e.jpg" />is arbitrary and <img src="5-7500717\b936ce95-b621-4792-ba13-8aa27456c4d4.jpg" /> is fixed, then</p><p><img src="5-7500717\eb944e5c-a87e-4ffd-9f5c-c258a8c89169.jpg" /></p><p><img src="5-7500717\39e9b81c-3d85-4fc7-8413-a80890af0962.jpg" /></p></sec><sec id="s3"><title>3. Special <img src="5-7500717\f304c25b-1fab-422a-bd8c-80f0cfc6600c.jpg" /> Algebras</title><p>Hamieh and Abbas [<xref ref-type="bibr" rid="scirp.22613-ref1">1</xref>] pass to a representation of the point <img src="5-7500717\673f964e-a15b-4b29-86f5-86aeb8c3756d.jpg" /> of the algebra <img src="5-7500717\7d21a79c-57e8-4941-b719-f3d7847ca8c0.jpg" /> in spherical coordinates, <img src="5-7500717\dd85a737-5aa4-4d74-ac97-ab1fe4ff9172.jpg" />and <img src="5-7500717\c6b53303-71e6-4c9f-8e46-1b5c91002f18.jpg" />. The subalgebras, called special <img src="5-7500717\8e3003fc-be30-4f65-b959-47e468205a7c.jpg" /> algebras and denoted by <img src="5-7500717\887bfd58-6143-47ff-ba0b-3f6f0e78737c.jpg" /> are the subalgebras spanned by all elements in which the “azimutal phase angle <img src="5-7500717\d0241e00-ec23-426a-885b-0221f9fc643e.jpg" /> is constant”. Each of these subalgebras is (isomorphic to) the complex numbers.</p><p>Lemma 4. The algebra <img src="5-7500717\147fdd94-1b1b-4789-95ce-791e40e0a78e.jpg" /> is isomorphic to an algebra of two by two matrices</p><p><img src="5-7500717\e95abff7-5ff3-4395-aa61-4e244e6f23ee.jpg" /></p><p>under the usual matrix operation of addition and multiplication.</p><p>Proof. The straight forward verification that the mapping <img src="5-7500717\e96bd96f-6b20-4f4c-b129-07b2b05ab565.jpg" /> is an isomorphism is left to the reader.</p><p>Lemma 5. Each of the algebras <img src="5-7500717\2d22eb7d-4a1b-4846-9a48-098028f3e5f9.jpg" /> is isomorphic to the complex numbers.</p><p>Proof. We note that if <img src="5-7500717\ccf31621-ff7d-44ba-817a-fd8b127a260f.jpg" /> then</p><p><img src="5-7500717\bbcb6270-b99b-46b7-9961-43cd8460fc72.jpg" />if<img src="5-7500717\38ffcc5a-ea43-4a6d-a150-9d382baddde4.jpg" />. If <img src="5-7500717\1cf6b7aa-06e3-4b17-b310-c878e7b40382.jpg" /> or<img src="5-7500717\a88195ce-0561-4c30-b571-413af046484c.jpg" />, then <img src="5-7500717\92dc01c8-4dd8-4cea-aa46-4ee730ab06ba.jpg" /> and the subalgebra <img src="5-7500717\7179d77d-f96e-4a19-93ea-03812780e18b.jpg" /> is (isomorphic to) the complex numbers. Otherwise, <img src="5-7500717\2244ad94-81a7-4727-b383-094f8251ca41.jpg" />or <img src="5-7500717\d89f12d6-804c-4327-b617-10d394abac04.jpg" /> for some<img src="5-7500717\d4c4068c-f5e4-4862-83fa-9795a7362eb5.jpg" />. Let<img src="5-7500717\856c5dfb-9dd4-43d5-ae3f-ca975ad675ca.jpg" />, then</p><p><img src="5-7500717\dc10f448-0e9d-4b21-a2f1-8b5e80e25d80.jpg" /></p><p>The multiplication, using the basis <img src="5-7500717\46bc196d-d177-4c15-91d3-ad567fc68105.jpg" /> will be given by</p><p><img src="5-7500717\b75aaad0-e952-4fa6-be26-fefcbd63ba7a.jpg" /></p></sec><sec id="s4"><title>4. The Spinor Matrices</title><p>The classical reference on spinors and wave equations is the book by Corson [<xref ref-type="bibr" rid="scirp.22613-ref16">16</xref>].</p><p>The associator spinor matrices are</p><p><img src="5-7500717\294b3b51-961f-4f72-934f-787af2dcb60f.jpg" />, <img src="5-7500717\75bd2f4d-f3d4-48c3-aaef-1af9eb1ed478.jpg" />, <img src="5-7500717\4e1aa0ba-767a-4098-bb77-786dfba47c95.jpg" />, <img src="5-7500717\91597064-90af-4da2-b8ae-299f2cec2a34.jpg" /></p><p>where<img src="5-7500717\3767ae74-507a-45f1-8975-f5bbf2d12588.jpg" />. Denoting the 2 by 2 identity matrix by<img src="5-7500717\8c52d857-fc7e-441a-b084-71ec9a532dad.jpg" />, these matrices satisfy</p><p><img src="5-7500717\33d7f99a-909e-4a80-95d2-747fcc917450.jpg" /></p><p>The spinor matrices generate a 6-dimensional real algebra with elements</p><p><img src="5-7500717\8f8eaef2-feb1-439a-891c-31b96d9f1ba2.jpg" /></p><p>that contains the matrix representation of the <img src="5-7500717\cd1a8da2-1a33-4b6e-bad3-ff6021560502.jpg" /> algebra. Denote this algebra by<img src="5-7500717\67bb5c07-800c-41fd-a367-24bedbaee258.jpg" />.</p><p>Lemma 6. The algebra <img src="5-7500717\e1240509-9d52-4f93-a54c-f0e7618f37be.jpg" /> is a quadratic algebra.</p><p>Proof. If <img src="5-7500717\21b3d217-3fa0-411c-bf8c-3668ff824371.jpg" /> is an element of<img src="5-7500717\037d8b91-e85a-4a0d-8227-9ef9aa924fee.jpg" />, then</p><p><img src="5-7500717\b706373f-4d6c-418a-a3c5-1cfa61363911.jpg" /></p><p><img src="5-7500717\3adea5c1-5f9e-4de3-b574-9edfb27fd827.jpg" /></p><p>Adding the left and right sides gives</p><p><img src="5-7500717\e0fb808f-0327-4635-9736-332cad0a8d45.jpg" /></p><p>Lemma 7. The algebra <img src="5-7500717\6dc75308-fcc1-427e-91d3-fb085a5a0046.jpg" /> is flexible.</p><p>Proof. Because of the trilinearlty of the associator, we can write the elements x and y of the associator <img src="5-7500717\1dec7582-30e0-4475-a717-cc0d5cd17144.jpg" /></p><p>as <img src="5-7500717\136b65c2-2f77-4594-b299-1455243f82f9.jpg" /> and<img src="5-7500717\161d3273-4705-493d-85b1-40ea3515d6f6.jpg" />. Then</p><p><img src="5-7500717\6bc18da3-3b23-4346-aa90-b3f9b0a89357.jpg" /></p><p><img src="5-7500717\f787b88e-bb25-4bdf-949c-1219d813ebcb.jpg" /></p><p><img src="5-7500717\cd6d8104-abb6-483c-9c00-e7046599ae63.jpg" /></p><p><img src="5-7500717\7348140f-2a99-4526-9cea-74824160a164.jpg" /></p><p>Theorem 1. The algebra <img src="5-7500717\5bbc0337-0aa2-457f-9685-0c2106f698b1.jpg" /> is a quadratic noncommutative Jordan algebra.</p></sec><sec id="s5"><title>5. The Dirac Equation</title><p>We proceed as in Hamieh and Abbas [<xref ref-type="bibr" rid="scirp.22613-ref1">1</xref>]. The Dirac equation over the complex numbers is often written as</p><p><img src="5-7500717\89dce548-4d8b-413c-96bb-f9d9df93e56d.jpg" /></p><p>utilizing the Einstein summation convention for <img src="5-7500717\16283b24-7896-4ebb-9a8f-9260913433da.jpg" /> <img src="5-7500717\0af505ea-fc6a-4ef9-bb72-6fc266543b56.jpg" />. A more general form is, setting</p><p><img src="5-7500717\33209817-3847-4486-a674-6946c6f2f6e2.jpg" /></p><p><img src="5-7500717\ca578853-7225-4dfa-97a7-7fdbdc5d7008.jpg" /></p><p>where<img src="5-7500717\b2c972f1-5aee-4621-bde3-81eec638b831.jpg" />.</p><p>Upon substituting the matrices for <img src="5-7500717\ae2188fe-681e-4b23-9951-d876da73f7c4.jpg" /> and simplifying we get</p><p><img src="5-7500717\bcbe26e3-3e7e-452c-97e8-71880e91946a.jpg" /></p><p>In dimensions x and t, the solution is given by</p><p><img src="5-7500717\953b95dd-678a-467e-809a-bca229acd3f2.jpg" /></p><p>p and <img src="5-7500717\665ab003-f8a2-4392-bb35-1fa2b831586e.jpg" /> are respect the momentum and energy. N is a normalization factor.</p></sec><sec id="s6"><title>6. Conclusion</title><p>We have shown that the <img src="5-7500717\dbbdf185-6026-47ea-b2b7-5ecbda68eda0.jpg" /> algebra belongs to a large class of Jordan algebras and have examined a few of the algebraic properties of these algebras and, like the Jordan algebra and the algebra of color, there is a very rich mathematical structure to further explore.</p></sec><sec id="s7"><title>REFERENCES</title></sec><sec id="s8"><title>NOTES</title></sec></body><back><ref-list><title>References</title><ref id="scirp.22613-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">S. Hamieh and H. Abbas, “Two Dimensional Representation of the Dirac Equation in Non-Associative Algebra,” Journal of Modern Physics, Vol. 3, No. 2, 2012, pp. 184-186. doi:10.4236/jmp.2012.32025</mixed-citation></ref><ref id="scirp.22613-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">P. Jordan, J. von Neumann and E. 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