Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological split-ring resonator based metamaterials with $\cal PT$
  symmetry relying on gain and loss   A one-dimensional metamaterial with parity-time (${\cal PT}$) symmetry that
relies on balanced gain and loss is introduced, comprising of magnetically
coupled split-ring resonators (SRRs). A particular topology that combines a
non-trivial (topological) dimer configuration with a trivial (non-topological)
dimer configuration which are separated by a central SRR with neither gain or
loss, is investigated. By focusing on the dynamical aspects of such a
topological ${\cal PT}$ metamaterial (PTMM), the existence of {\em
topologically protected interface states} which are localized at the central
SRR is demonstrated numerically. The solution of the corresponding {\em
quadratic eigenvalue problem} reveals that the protected state is actually a
robust eigenmode of the topological PTMM, whose eigenvalue is isolated in the
middle of the gap (mid-gap state) of the two-band frequency spectrum. Direct
numerical simulations have been further used to determine the robustness and
dynamic stability of these states in the parameter space of the {\em
dimerization strength} and the {\em gain-loss coefficient}.

31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
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The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys