Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A New Mathematical Formulation for a Phase Change Problem with a Memory
  Flux   A mathematical model for a one-phase change problem (particularly a Stefan
problem) with a memory flux, is obtained. The hypothesis that the weighted sum
of fluxes back in time is proportional to the gradient of temperature is
considered. The model obtained involves fractional derivatives with respect on
time in the sense of Caputo and in the sense of Riemann--Liouville. An integral
relationship for the free boundary which is equivalent to the `fractional
Stefan condition' is also obtained.

27
The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
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The categories of this paper are: funct-an
9
The categories of this paper are: nlin
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The categories of this paper are: atom-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int