Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The theory of stochastic cosmological lensing   On the scale of the light beams subtended by small sources, e.g. supernovae,
matter cannot be accurately described as a fluid, which questions the
applicability of standard cosmic lensing to those cases. In this article, we
propose a new formalism to deal with small-scale lensing as a diffusion
process: the Sachs and Jacobi equations governing the propagation of narrow
light beams are treated as Langevin equations. We derive the associated
Fokker-Planck-Kolmogorov equations, and use them to deduce general analytical
results on the mean and dispersion of the angular distance. This formalism is
applied to random Einstein-Straus Swiss-cheese models, allowing us to: (1) show
an explicit example of the involved calculations; (2) check the validity of the
method against both ray-tracing simulations and direct numerical integrations
of the Langevin equation. As a byproduct, we obtain a
post-Kantowski-Dyer-Roeder approximation, accounting for the effect of tidal
distortions on the angular distance, in excellent agreement with numerical
results. Besides, the dispersion of the angular distance is correctly
reproduced in some regimes.

14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg