Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum Physics, Relativity, and Complex Spacetime: Towards a New
  Synthesis   The positivity of the energy in relativistic quantum mechanics implies that
wave functions can be continued analytically to the forward tube T in complex
spacetime. For Klein-Gordon particles, we interpret T as an extended (8D)
classical phase space containing all 6D classical phase spaces as symplectic
submanifolds. The evaluation maps $e_z: f\to f(z)$ of wave functions on T are
relativistic coherent states reducing to the Gaussian coherent states in the
nonrelativistic limit. It is known that no covariant probability interpretation
exists for Klein-Gordon particles in real spacetime because the time component
of the conserved "probability current" can attain negative values even for
positive-energy solutions. We show that this problem is solved very naturally
in complex spacetime, where $|f(x-iy)|^2$ is interpreted as a probability
density on all 6D phase spaces in T which, when integrated over the "momentum"
variables y, gives a conserved spacetime probability current whose time
component is a positive regularization of the usual one. Similar results are
obtained for Dirac particles, where the evaluation maps $e_z$ are spinor-valued
relativistic coherent states. For free quantized Klein-Gordon and Dirac fields,
the above formalism extends to n-particle/antiparticle coherent states whose
scalar products are Wightman functions. The 2-point function plays the role of
a reproducing kernel for the one-particle and antiparticle subspaces.

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The categories of this paper are: physics
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The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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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: bayes-an
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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg