Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the energy-momentum tensor in Moyal space   We study the properties of the energy-momentum tensor of gauge fields coupled
to matter in non-commutative (Moyal) space. In general, the non-commutativity
affects the usual conservation law of the tensor as well as its transformation
properties (gauge covariance instead of gauge invariance). It is known that the
conservation of the energy-momentum tensor can be achieved by a redefinition
involving another star-product. Furthermore, for a pure gauge theory it is
always possible to define a gauge invariant energy-momentum tensor by means of
a Wilson line. We show that the latter two procedures are incompatible with
each other if couplings of gauge fields to matter fields (scalars or fermions)
are considered: The gauge invariant tensor (constructed via Wilson line) does
not allow for a redefinition assuring its conservation, and vice-versa the
introduction of another star-product does not allow for gauge invariance by
means of a Wilson line.

18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci