Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermorefringent noise in crystalline optical materials   Any material in thermal equilibrium exhibits fundamental thermodynamic
fluctuations of its mechanical and optical properties. Such thermodynamic
fluctuations of length, elastic constants, and refractive index of amorphous
materials -- like dielectric mirror coatings and substrates -- limit the
performance of today's most precise optical instruments. Crystalline materials
are increasingly employed in optical systems because of their reduced
mechanical dissipation, which implies a reduction of thermo-mechanical
fluctuations. However, the anisotropy of the crystalline state implies a
fundamental source of thermal noise: depolarization induced by thermal
fluctuations of its birefringence. We establish the theory of this effect,
elucidate its consequences, discuss its relevance for precision optical
experiments with crystalline materials, and hint at the conditions under which
it can be evaded.

17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph