The semi-infinite Goresky-MacPherson extension conjecture

Let GG be a reductive group, let G\sOG_{\sO} be the positive-loop subgroup, let \CF\CF be an irreducible perverse sheaf on G\sOG_{\sO}, and let ii denote the locally closed embedding into the relevant arc-space compactification. Let fi!\CFf_{i_{!*}\CF} be the would-be Goresky-MacPherson extension function, let VV be the representation associated with ρ\rho, let aχa_{\chi} act on an irreducible representation VV by multiplication by qi(χ,V)q^{i(\chi,V)}, and let SS be the Satake isomorphism.

Semi-infinite extension conjecture. If \CF\CF is the constant sheaf on G\sOG_{\sO}, then fi!\CFf_{i_{!*}\CF} corresponds under the Satake isomorphism to S(aχ([Sym(V)]))S(a_{\chi}([\operatorname{Sym}(V)])). If (V,ρ)(V,\rho) is irreducible, nZn\in\mathbb{Z}, Gn={gG\sF:v(χ(g))=n}G_n=\{g\in G_{\sF}:v(\chi(g))=n\}, and \CF\CF is supported on G0G_0, then

(fi!\CF)Gnqni(χ,V)f\CFρ,(n).(f_{i_{!*}\CF})|_{G_n}\simeq q^{n\cdot i(\chi,V)}f_{\CF_{\rho,(n)}}.

The first assertion is known for the constant sheaf in the torus and irreducible cases, while the text presents the general formulation as conjectural.

Sources & referencesView supporting material

Primary source

Roman Bezrukavnikov, Alexander Braverman, Michael Finkelberg and David Kazhdan, “A fusion construction of local L-factors”, arXiv:2303.00913 (2024).

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