Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral isoperimetric inequality for the $\delta'$-interaction on a
  contour   We consider the problem of geometric optimization for the lowest eigenvalue
of the two-dimensional Schr\"odinger operator with an attractive
$\delta'$-interaction of a fixed strength, the support of which is a
$C^2$-smooth contour. Under the constraint of a fixed length of the contour, we
prove that the lowest eigenvalue is maximized by the circle. The proof relies
on the min-max principle and the method of parallel coordinates.

19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an