**SMS scnews item created by John Enyang at Mon 22 Oct 2012 1024**

Type: Seminar

Distribution: World

Expiry: 27 Oct 2012

**Calendar1: 26 Oct 2012 1205-1255**

**CalLoc1: Carslaw 175**

Auth: enyang@penyang.pc (assumed)

### Algebra Seminar

# Euler characteristic of Hecke algebras

### Terragni

###### Friday 26th October, 12:05--12:55pm, Carslaw 175

###### Speaker:

Tommaso Terragni (University of Sydney)

###### Title:

Euler characteristic of Hecke algebras

###### Abstract:

By an old result of Serre, (finitely generated) Coxeter groups admit an Euler characteristic, and this can be computed by evaluating the inverse of the Poincaré series at 1. The Poincaré series itself can be computed through a recursive, alternating-sum formula (Steinberg, Solomon), which is in general meaningless for the corresponding evaluation.

Thus, the Poincaré series looks like an Euler character, much more than its evaluation does.

In this talk we show that it is indeed the case: the Poincaré series of the Coxeter system appears as the (suitably defined) Euler characteristic of a (suitably defined) Hecke algebra.

---------------------------------------------------------------------------------------

After the seminar we will take the speaker to lunch.

See the Algebra Seminar web page for information about other seminars in the series.

John Enyang John.Enyang@sydney.edu.au