Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Boundary time crystals   In this work we introduce {\it boundary time-crystals}. Here {\it continuous}
time-translation symmetry breaking occurs only in a macroscopic fraction of a
many-body quantum system. After introducing their definition and properties, we
analyse in detail a solvable model where an accurate scaling analysis can be
performed. The existence of the boundary time crystals is intimately connected
to the emergence of a time-periodic steady state in the thermodynamic limit of
a many-body open quantum system. We also discuss connections to quantum
synchronisation.

11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin