Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Active Matter Class with Second-Order Transition to Quasi-Long-Range
  Polar Order   We introduce and study in two dimensions a new class of dry, aligning, active
matter that exhibits a direct transition to orientational order, without the
phase-separation phenomenology usually observed in this context. Characterized
by self-propelled particles with velocity reversals and ferromagnetic alignment
of polarities, systems in this class display quasi-long-range polar order with
continuously-varying scaling exponents and yet a numerical study of the
transition leads to conclude that it does not belong to the
Berezinskii-Kosterlitz-Thouless universality class, but is best described as a
standard critical point with algebraic divergence of correlations. We
rationalize these findings by showing that the interplay between order and
density changes the role of defects.

21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
1
The categories of this paper are: cs
16
The categories of this paper are: stat
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an