Special Lectures in Real & Complex Geometry

Thursday, 5.3.2009, 17:00-17:40, place: Schreiber 309

Note special day and time!

Hannah Markwig, Georg-August-University Göttingen

Counting tropical plane elliptic curves with fixed j-invariant


Abstract
             
In tropical geometry, algebraic curves are replaced by piece-wise linear degenerations called tropical curves. Even though we "lose a lot of information" with this degeneration, many properties of the algebraic curve can be read off the tropical curve, and many theorems that hold for algebraic curves can be shown on the tropical side. One of the fields in which tropical geometry has had a lot of successrecently is enumerative geometry. In this talk, we present an enumerativeinvariant - namely the number of plane elliptic curves of a given degree d with fixed j-invariant through 3d-1 points in general position - that can be read off the tropical side. We present a tropical way to determine these numbers. This talk follows a talk given by Thomas Markwig who shows how the j-invariant of a curve is reflected in the tropical  world. Joint work with Michael Kerber.