Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angular distribution of radiation by relativistic electrons in a thin
  crystal   The results of theoretical investigation of angular distributions of
radiation from a relativistic electron passing through a thin crystal at a
small angle to the crystal axis are presented. The electron trajectories in
crystal were simulated using the binary collision model which takes into
account both coherent and incoherent effects at scattering. The angular
distribution of radiation was calculated as a sum of radiation from each
electron. It is shown that there are nontrivial angular distributions of the
emitted photons, which is connected to the superposition of the coherent
scattering of electrons by atomic rows (doughnut scattering effect) and the
suppression of the radiation due to the multiple scattering effect (similar to
the Landau-Pomeranchuk-Migdal effect in an amorphous matter). The orientation
dependence of angular distribution of radiation is also analyzed.

25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th