Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scaling and self-similarity in an unforced flow of inviscid fluid
  trapped inside a viscous fluid in a Hele-Shaw cell   We investigate quasi-two-dimensional relaxation, by surface tension, of a
long straight stripe of inviscid fluid trapped inside a viscous fluid in a
Hele-Shaw cell. Combining analytical and numerical solutions, we describe the
emergence of a self-similar dumbbell shape and find non-trivial dynamic
exponents that characterize scaling behavior of the dumbbell dimensions.

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The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph