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arXiv · 1708.06663

K-orbit closures and Barbasch-Evens-Magyar varieties

Laura Escobar·Benjamin J. Wyser·Alexander Yong
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Abstract

We define the Barbasch-Evens-Magyar varieties. We show they are isomorphic to the smooth varieties defined in [D.~Barbasch-S.~Evens '94] that map generically finitely to symmetric orbit closures, thereby giving resolutions of singularities in certain cases. Our definition parallels [P.~Magyar '98]'s construction of the Bott-Samelson varieties [H.~C.~Hansen '73, M.~Demazure '74]. From this alternative viewpoint, one deduces a graphical description in type $A$, stratification into closed subvarieties of the same kind, and determination of the torus-fixed points. Moreover, we explain how these manifolds inherit a natural symplectic structure with Hamiltonian torus action. We then express the moment polytope in terms of the moment polytope of a Bott-Samelson variety.

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Laura Escobar, Benjamin J. Wyser, Alexander Yong. 2017-08-22. K-orbit closures and Barbasch-Evens-Magyar varieties. https://doi.org/10.2140/pjm.2022.320.103

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