Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An exactly solvable toy model   In an attempt to regularize a previously known exactly solvable model [Yang
and Zhang, Eur. J. Phys. \textbf{40}, 035401 (2019)], we find yet another
exactly solvable toy model. The interesting point is that while the Hamiltonian
of the model is parameterized by a function $f(x)$ defined on $[0, \infty )$,
its spectrum depends only on the end values of $f$, i.e., $f(0)$ and $f(\infty
)$. This model can serve as a good exercise in quantum mechanics at the
undergraduate level.

5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph