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Understanding the second quantization of fermions in Clifford and in Grassmann space -- New way of second quantization of fermions, Part I

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 نشر من قبل Norma Susana Mankoc Borstnik
 تاريخ النشر 2020
  مجال البحث فيزياء
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Both algebras, Clifford and Grassmann, offer basis vectors for describing the internal degrees of freedom of fermions. The oddness of the basis vectors, transferred to the creation operators, which are tensor products of the finite number of basis vectors and the infinite number of momentum basis, and to their Hermitian conjugated partners annihilation operators, offers the second quantization of fermions without postulating the conditions proposed by Dirac, enabling the explanation of the Diracs postulates. But while the Clifford fermions manifest the half integer spins -- in agreement with the observed properties of quarks and leptons and antiquarks and antileptons -- the Grassmann fermions manifest the integer spins. In Part I properties of the creation and annihilation operators of integer spins Grassmann fermions are presented and the proposed equations of motion solved. The anticommutation relations of second quantized integer spin fermions are shown when applying on the vacuum state as well as when applying on the Hilbert space of the infinite number of Slater determinants with all the possibilities of empty and occupied fermion states. In Part II the conditions are discussed under which the Clifford algebras offer the appearance of the second quantized fermions, enabling as well the appearance of families. In both parts, Part I and Part II, the relation between the Dirac way and our way of the second quantization of fermions is presented.



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We present in Part II the description of the internal degrees of freedom of fermions by the superposition of odd products of the Clifford algebra elements, either $gamma^a$s or $tilde{gamma}^a$s, which determine with their oddness the anticommuting p roperties of the creation and annihilation operators of the second quantized fermion fields in even $d$-dimensional space-time, as we do in Part I of this paper by the Grassmann algebra elements $theta^a$s and $frac{partial}{partial theta_a}$s. We discuss: {bf i.} The properties of the two kinds of the odd Clifford algebras, forming two independent spaces, both expressible with the Grassmann algebra of $theta^{a}$s and $frac{partial}{partial theta_{a}}$s. {bf ii.} The freezing out procedure of one of the two kinds of the odd Clifford objects, enabling that the remaining Clifford objects determine with their oddness in the tensor products of the finite number of the Clifford basis vectors and the infinite number of momentum basis, the creation and annihilation operators carrying the family quantum numbers and fulfilling the anticommutation relations of the second quantized fermions: on the vacuum state, and on the whole Hilbert space defined by the sum of infinite number of Slater determinants of empty and occupied single fermion states. {bf iii.} The relation between the second quantized fermions as postulated by Dirac and the ones following from our Clifford algebra creation and annihilation operators, what offers the explanation for the Dirac postulates.
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