Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Eighty New Invariants of N-Periodics in the Elliptic Billiard   We introduce several-dozen experimentally-found invariants of Poncelet
N-periodics in the confocal ellipse pair (Elliptic Billiard). Recall this
family is fully defined by two integrals of motion (linear and angular
momentum), so any "new" invariants are dependent upon them. Nevertheless,
proving them may require sophisticated methods. We reference some two-dozen
proofs already contributed. We hope this article will motivate contributions
for those still lacking proof.

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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc