The semi-infinite Goresky-MacPherson extension conjecture

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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, n∈Zn\in\mathbb{Z}, Gn={g∈G\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)∣Gn≃qn⋅i(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.

References

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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