Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Charge Conjugation, Heavy Ions, e^+ e^- pairs: Was there a better way to
  add potentials to Dirac's free electrons?   This is a study of a possible alternative procedure for adding a potential
energy to the free electron Dirac equation. When Dirac added potentials to his
free electron equation, there were two alternatives (here called D1 and D2). He
chose D1 and lost charge conjugation symmetry, found Ehrenfest equations that
depended on the sign of the energy of the state determining the expectation
value, encountered Klein tunneling, zitterbewegung and the Klein paradox. The
D1 alternative also predicted that deep potentials should pull positive energy
states down into the negative energy continuum, possibly creating an unstable
vacuum. Extensive experiments (1975-1997) found no evidence for this
instability, but did find low energy electron-positron pairs with sharply
defined energies and unusually low counting statistics. These pairs tended to
disappear with higher beam currents. This paper explores the other alternative,
here called D2 and finds charge conjugation symmetry preserved, Ehrenfest
equations are classical, Klein tunneling is not present, unstable vacuua are
forbidden, zitterbewegung is absent in the charge current density, new
excitations of bound electron-positron pairs are possible in atoms, and the
energies at which low energy electron-positron pair production in heavy ion
scattering occurs is well described. Also all of the positive energy
calculations, including those with the Coulomb potential, the hydrogen-like
atom, are retained exactly the same as found in alternative D1. It might have
been better if Dirac had chosen alternative D2.

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The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
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The categories of this paper are: stat
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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: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: eess