Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dirac brackets from magnetic backgrounds   In symplectic mechanics, the magnetic term describing the interaction between
a charged particle and an external magnetic field has to be introduced by hand.
On the contrary, in generalised complex geometry, such magnetic terms in the
symplectic form arise naturally by means of B-transformations. Here we prove
that, regarding classical phase space as a generalised complex manifold, the
transformation law for the symplectic form under the action of a weak magnetic
field gives rise to Dirac's prescription for Poisson brackets in the presence
of constraints.

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The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: cond-mat
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg