Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spatial contraction of the Poincare group and Maxwell's equations in the
  electric limit   The contraction of the Poincare group with respect to the space trans-
lations subgroup gives rise to a group that bears a certain duality relation to
the Galilei group, that is, the contraction limit of the Poincare group with
respect to the time translations subgroup. In view of this duality, we call the
former the dual Galilei group. A rather remarkable feature of the dual Galilei
group is that the time translations constitute a central subgroup. Therewith,
in unitary irreducible representations (UIR) of the group, the Hamiltonian
appears as a Casimir operator proportional to the identity H = EI, with E (and
a spin value s) uniquely characterizing the representation. Hence, a physical
system characterized by a UIR of the dual Galilei group displays no non-trivial
time evolution. Moreover, the combined U(1) gauge group and the dual Galilei
group underlie a non- relativistic limit of Maxwell's equations known as the
electric limit. The analysis presented here shows that only electrostatics is
possible for the electric limit, wholly in harmony with the trivial nature of
time evolution governed by the dual Galilei group.

16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn