Isotropical linear spaces and valuated Delta-matroids

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Abstract

The spinor variety is cut out by the quadratic Wick relations among the principal Pfaffians of an n×n skew-symmetric matrix. Its points correspond to n-dimensional isotropic subspaces of a 2n-dimensional vector space. In this paper we tropicalize this picture, and we develop a combinatorial theory of tropical Wick vectors and tropical linear spaces that are tropically isotropic. We characterize tropical Wick vectors in terms of subdivisions of Δ-matroid polytopes, and we examine to what extent the Wick relations form a tropical basis. Our theory generalizes several results for tropical linear spaces and valuated matroids to the class of Coxeter matroids of type D.

Keywords

Tropical linear space
Isotropic subspace
Delta matroid
Coxeter matroid
Valuated matroid
Spinor variety
Wick relations
Matroid polytope
Tropical basis

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