Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mixing for Time-Changes of Heisenberg Nilflows   We consider reparametrizations of Heisenberg nilflows. We show that if a
Heisenberg nilflow is uniquely ergodic, all non-trivial time-changes within a
dense subspace of smooth time-changes are mixing. Equivalently, in the language
of special flows, we consider special flows over linear skew-shift extensions
of irrational rotations of the circle. Without assuming any Diophantine
condition on the frequency, we define a dense class of smooth roof functions
for which the corresponding special flows are mixing. Mixing is produced by a
mechanism known as stretching of Birkhoff sums. The complement of the set of
mixing time-changes (or, equivalently, of mixing roof functions) has countable
codimension and can be explicitely described in terms of the invariant
distributions for the nilflow (or, equivalently, for the skew-shift), allowing
to produce concrete examples of mixing time-changes.

34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg