## EVENT DETAILS AND ABSTRACT

**Geometry/Physics Seminar**
**Title:** Enumerative invariants of simple antibirational involutions on symplectic\r\n4-manifolds

**Speaker:** Professor Jean-Yves Welschinger

**Speaker Info:** MSRI, École normale supérieure de Lyon

**Brief Description:**

**Special Note**:

**Abstract:**

I will first construct invariants under deformation of real symplectic
4-manifolds, following the approach of Gromov and Witten. These invariants
are obtained via an algebraic count of the number of real
rational J-holomorphic curves which realize a given homology class and
pass through the
appropriate number of points, with respect to some sign that we first
define. These invariants provide lower bounds in real enumerative
geometry, namely for the total number of such real rational curves.
Then, I will introduce the notion of antibirational involutions on
symplectic 4-manifolds and show how these results can be extended to
simple ones. The latter part is still in progress.

**Date:** Thursday, April 29, 2004

**Time:** 4:00pm

**Where:** Lunt 104

**Contact Person:** Prof. Cheolhyun Cho

**Contact email:** cho@math.northwestern.edu

**Contact Phone:** 847-467-1634

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