Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Geometric multiplicity of unitary non-backtracking eigenvalues   We completely characterize the conditions under which a complex unitary
number is an eigenvalue of the non-backtracking matrix of an undirected graph.
Further, we provide a closed formula to compute its geometric multiplicity and
describe an algorithm to compute this multiplicity without making a single
matrix computation. The algorithm has time complexity that is linear in the
size of the graph.

34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat