Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: General properties of fidelity in non-Hermitian quantum systems with PT
  symmetry   The fidelity susceptibility is a tool for studying quantum phase transitions
in the Hermitian condensed matter systems. Recently, it has been generalized
with the biorthogonal basis for the non-Hermitian quantum systems. From the
general perturbation description with the constrain of parity-time (PT)
symmetry, we show that the fidelity $\mathcal{F}$ is always real for the
PT-symmetric states. For the PT-broken states, the real part of the fidelity
susceptibility equals to one half of the sum of the fidelity susceptibility of
the PT-broken and the PT-partner states, $\mathrm{Re}[\mathcal{X}_F] =
\frac{1}{2}(\mathcal{X}_F +\bar{\mathcal{X}}_F)$. The negative infinity of the
fidelity susceptibility is explored by the perturbation theory when the
parameter approaches the exceptional point (EP). Moreover, at the second-order
EP where two eigenstates and eigenenergies coalesce, we prove that the real
part of the fidelity between PT-symmetric and PT-broken states is
$\mathrm{Re}\mathcal{F}=\frac{1}{2}$. We demonstrate these general properties
for non-interacting and interacting systems by two examples: the two-legged
non-Hermitian Su-Schrieffer-Heeger (SSH) model and the non-Hermitian XXZ spin
chain.

23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex