Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rigid actions have zero entropy   Rigid actions have zero Rokhlin entropy and nonpositive sofic entropy.
Because rigidity is a stable orbit-equivalence invariant, this provides the
first example of an essentially free, ergodic, probability-measure-preserving
action of the free group that has nonpositive sofic entropy and any essentially
free action stably-orbit-equivalent to it also has nonpositive sofic entropy.

17
The categories of this paper are: q-fin
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The categories of this paper are: eess
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys