Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Patterns of Lorentz symmetry breaking in QED by CPT-odd interaction   A tiny Lorentz symmetry breaking can be mediated in Electrodynamics by means
of the Chern-Simons (CS) interaction polarized along a constant CS vector. Its
presence makes the vacuum optically active that has been recently estimated
from astrophysical data. We examine two possibilities for the CS vector to be
time-like or space-like, under the assumption that it originates from v.e.v. of
some pseudoscalar matter. It is shown that: a) a time-like CS vector makes the
vacuum unstable under pairs creation of tachyonic photon modes with the finite
vacuum decay rate, i.e. it is unlikely realized at macroscopic time scales; b)
on the contrary, the space-like CS vector does not yield any tachyonic modes
and, moreover, if its dynamical counterpart is substantially described by a
scale invariant interaction, then the QED radiation effects induce the
dynamical breaking of Lorentz symmetry, i.e. the occurrence of space-like CS
vector appears to be rather natural.

28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph