English

The Weyl groupoid in Type A, Young diagrams and Borel subalgebras

Combinatorics 2023-12-19 v1 Quantum Algebra Rings and Algebras Representation Theory

Abstract

Let k\mathtt{k} be an algebraically closed field of characteristic zero. Let go{\stackrel{{\rm o}}{{\mathfrak{g}}}} be the Lie superalgebra sl(nm){\mathfrak{sl}}(n|m) and let W\mathfrak{W} be the Weyl groupoid introduced by Sergeev and Veselov using the root system of go{\stackrel{{\rm o}}{{\mathfrak{g}}}}. An important subgroupoid Tiso\mathfrak T_{iso} of W{\mathfrak{W}} has base Δiso\Delta_{iso}, the set of all the isotropic roots. Motivated by deformed quantum Calogero-Moser problems, the same authors considered an action of W\mathfrak{W} on knm\mathtt{k}^{n|m} depending on a parameter κ\kappa. %When κ\kappa is negative special, they showed this action has infinite orbits. In the case m>nm>n, with m,nm,n relatively prime and κ=n/m\kappa=-n/m we study a particular infinite orbit of Tiso\mathfrak T_{iso} with some special properties. This orbit, thought of as a directed graph is isomorphic to the graph of an orbit for the action of Tiso\mathfrak T_{iso} on certain Borel subalgebras of the affinization L^(go){\widehat{L}(\stackrel{{\rm _o}}{{\mathfrak{g}}})} of go{\stackrel{{\rm o}}{{\mathfrak{g}}}}. %The root groupoid has a base consisting of Borel subalgebras with fixed even part, and morphisms are given by odd reflections. The underlying reason for this graph isomorphism is that both have combinatorics which can be described using Young diagrams and tableaux drawn on the surface of a rotating cylinder with circumference nn and length mm. Allowing the cylinder to rotate produces an infinite orbit. This leads to a third graph which is isomorphic to the other two.

Keywords

Cite

@article{arxiv.2312.11046,
  title  = {The Weyl groupoid in Type A, Young diagrams and Borel subalgebras},
  author = {Ian M. Musson},
  journal= {arXiv preprint arXiv:2312.11046},
  year   = {2023}
}

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