Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hawking-like radiation does not require a trapped region   We discuss the issue of quasi-particle production by ``analogue black holes''
with particular attention to the possibility of reproducing Hawking radiation
in a laboratory. By constructing simple geometric acoustic models, we obtain a
somewhat unexpected result: We show that in order to obtain a stationary and
Planckian emission of quasi-particles, it is not necessary to create a trapped
region in the acoustic spacetime (corresponding to a supersonic regime in the
fluid flow). It is sufficient to set up a dynamically changing flow
asymptotically approaching a sonic regime with sufficient rapidity in
laboratory time.

13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an