Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discrete Lagrangian reduction, discrete Euler-Poincare equations, and
  semidirect products   A discrete version of Lagrangian reduction is developed in the context of
discrete time Lagrangian systems on $G\times G$, where $G$ is a Lie group. We
consider the case when the Lagrange function is invariant with respect to the
action of an isotropy subgroup of a fixed element in the representation space
of $G$. In this context the reduction of the discrete Euler-Lagrange equations
is shown to lead to the so called discrete Euler-Poincar\'e equations. A
constrained variational principle is derived. The Legendre transformation of
the discrete Euler-Poincar\'e equations leads to discrete Hamiltonian
(Lie-Poisson) systems on a dual space to a semiproduct Lie algebra.

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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
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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: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: cs
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin