Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Discrete Analog of the Malgrange-Ehrenpreis Theorem   One of the landmarks of the modern theory of partial differential equations
is the Malgrange- Ehrenpreis theorem that states that every non-zero linear
partial differential operator with constant coefficients has a Green function
(alias fundamental solution). In this short note I state the discrete analog,
and give two proofs. The first one is Ehrenpreis- style, using duality, and the
second one is constructive, using formal Laurent series.
  This article is accompanied by the Maple package LEON available from:
http://www.math.rutgers.edu/~zeilberg/tokhniot/LEON .

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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas