Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Salpeter equation and probability current in the relativistic
  Hamiltonian quantum mechanics   The probablity current for a quantum spinless relativistic particle is
introduced based on the Hamiltonian dynamics approach utilizing the Salpeter
equation as an alternative of the Klein-Gordon equation. The correctness of the
presented formalism is illustrated by examples of exact solutions to the
Salpeter equation including the new ones introduced in this work.

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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas