Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Noiseless limit of a ferrofluid ratchet   The noiseless limit of a thermal ratchet device using ferrofluids is studied
in detail. Contrary to previous claims it is proved that no directed transport
can occur in this model in the absence of fluctuations.

29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
18
The categories of this paper are: econ
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg