Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The continuum limit of a 4-dimensional causal set scalar d'Alembertian   The continuum limit of a 4-dimensional, discrete d'Alembertian operator for
scalar fields on causal sets is studied. The continuum limit of the mean of
this operator in the Poisson point process in 4-dimensional Minkowski spacetime
is shown to be the usual continuum scalar d'Alembertian $\Box$. It is shown
that the mean is close to the limit when there exists a frame in which the
scalar field is slowly varying on a scale set by the density of the Poisson
process. The continuum limit of the mean of the causal set d'Alembertian in
4-dimensional curved spacetime is shown to equal $\Box - \frac{1}{2}R$, where
$R$ is the Ricci scalar, under certain conditions on the spacetime and the
scalar field.

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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
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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: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph