Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The charmed string: self-supporting loops through air drag   The string shooter experiment uses counter-rotating pulleys to propel a
closed string forward. Its steady state exhibits a transition from a gravity
dominated regime at low velocity towards a high velocity regime where the
string takes the form of a self-supporting loop. Here we show that this loop of
light string is not suspended in the air due to inertia, but through the
hydrodynamic drag exerted by the surrounding fluid, namely air. We investigate
this drag experimentally and theoretically for a smooth long cylinder moving
along its axis. We then derive the equations describing the shape of the string
loop in the limit of vanishing string radius. The solutions present a critical
point, analogous to a hydraulic jump, separating a supercritical zone where the
wave velocity is smaller than the rope velocity, from a subcritical zone where
waves propagate faster than the rope velocity. This property could be leveraged
to create a white hole analogue similar to what has been demonstrated using
surface waves on a flowing fluid. Loop solutions that are regular at the
critical point are derived, discussed and compared to the experiment. In the
general case, however, the critical point turns out to be the locus of a sharp
turn of the string, which is modelled theoretically as a discontinuity. The
hydrodynamic regularisation of this geometrical singularity, which involves
non-local and added mass effects, is discussed based on dimensional analysis.

12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph