Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-Tiles and Walls - A Variant on the Heesch Problem   The Heesch problem 'grades' polygons that fail to tile the plane in terms of
the number of layers (or corollas) of copies of it that can be formed around a
central unit. We study the different topology of ' walls', which we define to
be simply connected regions that divide the plane exactly into two simply
connected regions. We present preliminary results and conjectures.

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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con