**Date & Time:** Thursday, October 22, 2009, 16:00-17:00.

**Venue:** Ramanujan Hall

**Title:** On the Basis Problem for Elliptic Modular Forms

**Speaker:** Siegfried Böcherer, Universität Mannheim

**Abstract:** Here we discuss, for a given genus of positive definite quadratic forms of squarefree level, which modular forms of squarefree level *N* can be represented by theta series from that genus; the case of newforms is well-known, but for the oldforms some surprising phenomenon arises, which is also interesting to compare with the representation theoretic theta correspondence (recent work of mine).