Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonreciprocal localization of ultrasound in a viscous medium with
  asymmetric scatterers   A two-dimensional phononic crystal with asymmetric scatterers is used for the
study of Anderson localization of sound along one-dimensional disorder produced
by random orientation of metallic rods. An exponentially weak transmission of
ultrasound is demonstrated for the waves propagating along the direction of
disorder. In the perpendicular direction where the scatterers are ordered,
sound propagates as extended wave. The {\it PT}-symmetry of the system is
broken by dissipative viscous losses and asymmetric shape of the scatterers.
Nonreciprocal transmission of sound is observed for both, ordered and
disordered, directions. In the localized regime, the nonreciprocity is
manifested through different values of localization length for sound
propagating in the opposite directions.

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The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex