Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on ``Time-like flows of energy-momentum and particle
  trajectories for the Klein-Gordon equation''   Horton, Dewdney, and Nesteruk [quant-ph/0103114] have proposed Bohm-type
particle trajectories accompanying a Klein-Gordon wave function psi on
Minkowski space. From two vector fields on space-time, W^+ and W^-, defined in
terms of psi, they intend to construct a timelike vector field W, the integral
curves of which are the possible trajectories, by the following rule: at every
space-time point, take either W = W^+ or W = W^- depending on which is
timelike.
  This procedure, however, is ill-defined as soon as both are timelike, or both
spacelike. Indeed, they cannot both be timelike, but they can well both be
spacelike, contrary to the central claim of [quant-ph/0103114]. We point out
the gap in their proof, provide a counterexample, and argue that, even for a
rather arbitrary wave function, the points where both W^+ and W^- are spacelike
can form a set of positive measure.

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The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: econ
20
The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
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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: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: eess