A Fourier transform for the quantum Toda lattice

Abstract

Abstract We answer a question of V. Drinfeld by constructing an ‘algebraic Fourier transform’ for the quantum Toda lattice of a complex reductive algebraic group G, which extends the classical ‘algebraic Fourier transform’ for its subalgebra

$$D(T)^W$$

D

( T )

W

of Weyl group invariant differential operators on a maximal torus. The proof is contained in Sect. 2 and relies on a result of Bezrukavnikov–Finkelberg realizing the quantum Toda lattice as the equivariant homology of the dual affine Grassmannian; the Fourier transform boils down to nothing more than the duality between homology and cohomology. In Sect. 3, we compare our result with a related result of V. Ginzburg, and explain the apparent discrepancy by showing that W-equivariant quasicoherent sheaves on

$${{\mathrm{\mathfrak {t}}}}^*$$

t

∗

descend to

$${{\mathrm{\mathfrak {t}}}}^*//W$$

t

∗

/ / W

if they descend to

$${{\mathrm{\mathfrak {t}}}}^*/\langle s_i\rangle $$

t

∗

/

⟨

s i

⟩

for every simple reflection

$$s_i$$

s i

of W.