Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous shell effect in the transition from a circular to a triangular
  billiard   We apply periodic orbit theory to a two-dimensional non-integrable billiard
system whose boundary is varied smoothly from a circular to an equilateral
triangular shape. Although the classical dynamics becomes chaotic with
increasing triangular deformation, it exhibits an astonishingly pronounced
shell effect on its way through the shape transition. A semiclassical analysis
reveals that this shell effect emerges from a codimension-two bifurcation of
the triangular periodic orbit. Gutzwiller's semiclassical trace formula, using
a global uniform approximation for the bifurcation of the triangular orbit and
including the contributions of the other isolated orbits, describes very well
the coarse-grained quantum-mechanical level density of this system. We also
discuss the role of discrete symmetry for the large shell effect obtained here.

22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ