Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Edge-following topological states   We prove that Chern insulators have topologically protected edge states which
not only propagate unidirectionally along a straight line boundary, but also
swerve around arbitrary-angled corners and geometric imperfections of the
material boundary. This is a physical manifestation of the index theory of
certain semigroup operator algebras.

17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat