Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-linear electrodynamics non-minimally coupled to
  gravity:symmetric-hyperbolicity and causal structure   It is shown here that symmetric hyperbolicity, which guarantees
well-posedness, leads to a set of two inequalities for matrices whose elements
are determined by a given theory. As a part of the calculation, carried out in
a mostly-covariant formalism, the general form for the symmetrizer, valid for a
general Lagrangian theory, was obtained. When applied to nonlinear
electromagnetism linearly coupled to curvature, the inequalities lead to strong
constraints on the relevant quantities, which were illustrated with
applications to particular cases. The examples show that non-linearity leads to
constraints on the field intensities, and non-minimal coupling imposes
restrictions on quantities associated to curvature.

11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con