Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Motility-Induced Microphase and Macrophase Separation in a
  Two-Dimensional Active Brownian Particle System   As a result of nonequilibrium forces, purely repulsive self-propelled
particles undergo macrophase separation between a dense and a dilute phase. We
present a thorough study of the ordering kinetics of such motility-induced
phase separation (MIPS) in active Brownian particles in two dimensions, and we
show that it is generically accompanied by microphase separation. The growth of
the dense phase follows a law akin to the one of liquid-gas phase separation.
However, it is made of a mosaic of hexatic microdomains whose size does not
coarsen indefinitely, leaving behind a network of extended topological defects
from which microscopic dilute bubbles arise. The characteristic length of these
finite-size structures increases with activity, independently of the choice of
initial conditions.

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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc