Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discrete Hamilton-Pontryagin mechanics and generating functions on Lie
  groupoids   We present a discrete analog of the recently introduced Hamilton-Pontryagin
variational principle in Lagrangian mechanics. This unifies two, previously
disparate approaches to discrete Lagrangian mechanics: either using the
discrete Lagrangian to define a finite version of Hamilton's action principle,
or treating it as a symplectic generating function. This is demonstrated for a
discrete Lagrangian defined on an arbitrary Lie groupoid; the often encountered
special case of the pair groupoid (or Cartesian square) is also given as a
worked example.

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The categories of this paper are: astro-ph
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The categories of this paper are: stat
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
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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: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga