Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superfluidity of Light and its Break-Down in Optical Mesh Lattices   Hydrodynamic phenomena can be observed with light thanks to the analogy
between quantum gases and nonlinear optics. In this Letter, we report an
experimental study of the superfluid-like properties of light in a
(1+1)-dimensional nonlinear optical mesh lattice, where the arrival time of
optical pulses plays the role of a synthetic spatial dimension. A spatially
narrow defect at rest is used to excite sound waves in the fluid of light and
measure the sound speed. The critical velocity for superfluidity is probed by
looking at the threshold in the deposited energy by a moving defect, above
which the apparent superfluid behaviour breaks down. Our observations establish
optical mesh lattices as a promising platform to study fluids of light in novel
regimes of interdisciplinary interest, including non-Hermitian and/or
topological physics.

2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph