Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear optical refraction of the dye-doped E7 thermotropic liquid
  crystal at the nematic-isotropic phase transition   It is known that the doping of liquid crystal with dyes usually changes the
physical properties of the host, like the transition temperatures and the
optical absorption among others. In this work we report a study of the
nonlinear optical refraction of a dye doped sample of the E7 thermotropic
liquid crystal by the Z-scan technique. It was found that the nonlinear
refraction of the sample is higher than the undoped one, diverging at the
clearing point. Close to the N-I transition, the nonlinear birefringence is
characterized by a critical exponent that seams to confirm the tricritical
hypothesis of the nature of the N-I phase transition, being independent of the
doping.

35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph