Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Three-dimensional higher-order topological acoustic system with
  multidimensional topological states   Topologically protected gapless edge/surface states are phases of quantum
matter which behave as massless Dirac fermions, immunizing against disorders
and continuous perturbations. Recently, a new class of topological insulators
(TIs) with gapped edge states and in-gap corner states have been theoretically
predicted in electric systems 1,2, and experimentally realized in
two-dimensional (2D) mechanical and electromagnetic systems 3,4, electrical
circuits 5, optical and sonic crystals 6-11, and elastic phononic plates 12.
Here, we elaborately design a strong three-dimensional (3D) topological
acoustic system, by arranging acoustic meta-atoms in a simple cubic lattice.
Under the direct field measurements, besides of the 2D surface propagations on
all of the six surfaces, the 1D hinge propagations behaving as robust acoustic
fibers along the twelve hinges and the 0D corner modes working as robust
localized resonances at the eight corners are experimentally confirmed. As
these multidimensional topological states are activated in different
frequencies and independent spaces, our works pave feasible ways for
applications in the topological acoustic cavities, communications and
signal-processing.

25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat