nLab Hecke category




Generally, for XYX \longrightarrow Y a suitable map of schemes or algebraic stacks, then the corresponding Hecke category is the category (derived category, (infinity,1)-category) 𝒟(X× YX)\mathcal{D}(X \times_Y X) of D-modules on the (homotopy) fiber product, regarded as a monoidal category by regarding its objects as specifying integral transforms in Fun 𝒟(Y)(𝒟(X),𝒟(X))Fun_{\mathcal{D}(Y)}(\mathcal{D}(X), \mathcal{D}(X)) (Ben-Zvi & Nadler 09, section 5.1).

For XYX\to Y the inclusion BBBG\mathbf{B}B \to \mathbf{B}G of the delooping of a Borel subgroup of a complex reductive group, then (generally for maps of delooped groups like this, see here at homotopy limit) the homotopy fiber product is X× YXB\\G//BX \times_Y X \simeq B \backslash \backslash G // B . The Hecke category for this case is the default case of Hecke categories used in geometric representation theory.

The concept of Hecke category is a categorification of that of Hecke algebra.


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