Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: O(d+1,d+n+1)--invariant Formulation of Stationary Heterotic String
  Theory   We present a pair of symmetric formulations of the matter sector of the
stationary effective action of heterotic string theory that arises after the
toroidal compactification of d dimensions. The first formulation is written in
terms of a pair of matrix potentials Z_1 and Z_2 which exhibits a clear
symmetry between them and can be used to generate new families of solutions on
the basis of either Z_1 or Z_2; the second one is an O(d+1,d+n+1)-invariant
formulation which is written in terms of a matrix vector W endowed with an
O(d+1,d+n+1)-invariant scalar product which linearizes the action of the
O(d+1,d+n+1) symmetry group on the coset space O(d+1,d+n+1)/[O(d+1)XO(d+n+1)];
this fact opens as well a simple solution--generating technique which can be
applied on the basis of known solutions. A special class of extremal solutions
is indicated by asuming a simple ansatz for the matrix vector W that reduces
the equation of motion to the Laplace equation for a real scalar function.

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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: physics
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The categories of this paper are: funct-an
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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: math
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The categories of this paper are: cs
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The categories of this paper are: bayes-an