Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Characterisation of First-Order Constraint Satisfaction Problems   We describe simple algebraic and combinatorial characterisations of finite
relational core structures admitting finitely many obstructions. As a
consequence, we show that it is decidable to determine whether a constraint
satisfaction problem is first-order definable: we show the general problem to
be NP-complete, and give a polynomial-time algorithm in the case of cores. A
slight modification of this algorithm provides, for first-order definable
CSP's, a simple poly-time algorithm to produce a solution when one exists. As
an application of our algebraic characterisation of first order CSP's, we
describe a large family of L-complete CSP's.

15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
2
The categories of this paper are: math
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The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: atom-ph