Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermal noise and mechanical loss of SiO$_2$/Ta$_2$O$_5$ optical
  coatings at cryogenic temperatures   Mechanical loss of dielectric mirror coatings sets fundamental limits for
both gravitational wave detectors and cavity-stabilized optical local
oscillators for atomic clocks. Two approaches are used to determine the
mechanical loss: ringdown measurements of the coating quality factor and direct
measurement of the coating thermal noise. Here we report a systematic study of
the mirror thermal noise from room temperature to 4 K by operating reference
cavities at these temperatures. The directly measured thermal noise is used to
extract the corresponding mechanical loss for SiO$_2$/Ta$_2$O$_5$ coatings,
which are compared with previously reported values.

5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
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The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
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The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th