Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solutions of Podolsky's Electrodynamics Equation in the First-Order
  Formalism   The Podolsky generalized electrodynamics with higher derivatives is
formulated in the first-order formalism. The first-order relativistic wave
equation in the 20-dimensional matrix form is derived. We prove that the
matrices of the equation obey the Petiau-Duffin-Kemmer algebra. The
Hermitianizing matrix and Lagrangian in the first-order formalism are given.
The projection operators extracting solutions of field equations for states
with definite energy-momentum and spin projections are obtained, and we find
the density matrix for the massive state. The $13\times 13$-matrix Schrodinger
form of the equation is derived, and the Hamiltonian is obtained. Projection
operators extracting the physical eigenvalues of the Hamiltonian are found.

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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci