Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Image distortion from optical scalars in non perturbative gravitational
  lensing   In a previous article concerning image distortion in non-perturbative
gravitational lensing theory we described how to introduce shape and distortion
parameters for small sources. We also showed how they could be expressed in
terms of the scalar products of the geodesic deviation vectors of the source's
pencil of rays in the past lightcone of an observer. In the present work we
give an alternative approach to the description of the shape and distortion
parameters and their evolution along the null geodesic from the source to the
observer, but now in terms of the optical scalars (the convergence and shear of
null vector field of the observer's lightcone) and the associated optical
equations, which relate the optical scalars to the curvature of the spacetime.

15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas