Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Regular electrically charged structures in Nonlinear Electrodynamics
  coupled to General Relativity   We address the question of existence of regular spherically symmetric
electrically charged solutions in Nonlinear Electrodynamics coupled to General
Relativity. Stress-energy tensor of the electromagnetic field has the algebraic
structure $T_0^0=T_1^1$. In this case the Weak Energy Condition leads to the de
Sitter asymptotic at approaching a regular center. In de Sitter center of an
electrically charged NED structure, electric field, geometry and stress-energy
tensor are regular without Maxwell limit which is replaced by de Sitter limit:
energy density of a field is maximal and gives an effective cut-off on
self-energy density, produced by NED coupled to gravity and related to
cosmological constant $\Lambda$. Regular electric solutions satisfying WEC,
suffer from one cusp in the Lagrangian ${\cal L}(F)$, which creates the problem
in an effective geometry whose geodesics are world lines of NED photons. We
investigate propagation of photons and show that their world lines never
terminate which suggests absence of singularities in the effective geometry. To
illustrate these results we present the new exact analytic spherically
symmetric electric solution with the de Sitter center.

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The categories of this paper are: physics
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
2
The categories of this paper are: math