Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The fourth dimension of the nucleon structure: spacetime analysis of the
  timelike electromagnetic proton form factors   As well known, spacelike proton form factors expressed in the Breit frame may
be interpreted as the Fourier transform of static space distributions of
electric charge and current. In particular, the electric form factor is simply
the Fourier transform of the charge distribution $F(q)=\int e^{i\vec q \cdot
\vec r} \rho(r)d^3r$. We don't have an intuitive interpretation of the same
level of simplicity for the proton timelike form factor appearing in the
reactions $e^+e^-\leftrightarrow \bar{p}p$. However, one may suggest that in
the center of mass (CM) frame, where $q_\mu x^\mu =qt$, a timelike electric
form factor is the Fourier transform $F(q) =\int e^{iqt} R(t)dt$ of a function
$R(t)$ expressing how the electric properties of the forming (or annihilating)
proton-antiproton pair evolve in time. Here we analyze in depth this idea, show
that the functions $\rho(r)$ and $R(t)$ can be formally written as the time and
space integrals of a unique correlation function depending on both time and
space coordinates.

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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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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: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin