A celebrated result of Farahat and Higman constructs an algebra FH which "interpolates" the centres Z(ZSn) of group algebras of the symmetric groups Sn
Nearby in the stack
. We extend these results from symmetric group algebras to type
A
Iwahori-Hecke algebras,
Hn(q)
. In particular, we explain how to construct an algebra
FHq
"interpolating" the centres
Z(Hn(q))
. We prove that
FHq
is isomorphic to
R[q,q−1]⊗ZΛ
(where
R
is the ring of integer-valued polynomials, and
Λ
is the ring of symmetric functions). The isomorphism can be described as "evaluation at Jucys-Murphy elements", leading to a proof of a conjecture of Francis and Wang. This yields character formulae for the Geck-Rouquier basis of
Z(Hn(q))
when acting on Specht modules.
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