Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermat's principle in quantum gravitational optics   Interactions incorporating the vacuum polarization effects in curved
backgrounds modify the null cone structure in such a way that the photon
trajectories would not be the space-time geodesics anymore. The gravitational
birefringence introduced as a direct consequence of these effects, will allow
shifts in the photon velocities leading to polarization dependent superluminal
propagation. Taking these effects into account we study Fermat's principle in
the context of the 1+3 (threading) formulation of the space-time decomposition.
We find an expression for the modified spacetime refractive index and show it
is proportional to the light cone correction to the first order. Consequences
of this modification on polarization sum rules and spatial light paths are
considered.

14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
3
The categories of this paper are: physics
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph