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The Springer variety is the set of flags stabilized by a nilpotent operator. In 1976, T.A. Springer observed that this variety's cohomology ring carries a symmetric group action, and he offered a deep geometric construction of this action. Sixteen years later, Garsia and Procesi made Springer's work more transparent and accessible by presenting the(More)
Nilpotent Hessenberg varieties are a family of subvarieties of the flag variety, which include the Springer varieties, the Peterson variety, and the whole flag variety. In this thesis I give a geometric proof that the cohomology of the flag variety surjects onto the cohomology of the Peterson variety; I provide a combinatorial criterion for determing the(More)
1. Cohomology of nilpotent Hessenberg varieties The Springer variety S X is defined to be the set of flags stabilized by a nilpotent operator X. Springer varieties can be generalized to a two-parameter family of varieties called Hessenberg varieties H(X, h), defined by a nilpotent operator X and a certain step function h (or equivalently, a Dyck path). In(More)
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