Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological exceptional surfaces in non-Hermitian systems with
  parity-time and parity-particle-hole symmetries   We study a topological band degeneracy in non-Hermitian systems with
parity-time ($PT$) and parity-particle-hole ($CP$) symmetries. In
$d$-dimensional non-Hermitian systems, it is shown that $(d-1)$-dimensional
exceptional surfaces can appear from band touching thanks to $PT$ or $CP$
symmetry. We investigate the topological stability and zero-gap quasiparticles
for the exceptional surfaces due to the band degeneracy. We also demonstrate
the band degeneracy by using lattice models of a topological semimetal and a
superconductor.

15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph