Alexei Kolesnikov : Eliminating groupoid imaginaries in first-order theories

Posted by , part of the Logic Seminar.

At

April 14, 2009, 4 p.m.

In

SEO 612

Abstract

A recent work of Hrushovski links failure of certain amalgamation properties to definability of groupoids in stable theories. In a joint work with John Goodrick, we provide an explicit construction of such groupoids, show that the groupoids can be non-trivial even in a totally categorical theory, and obtain a way to ``eliminate'', in a certain sense, such groupoids by adding additional sorts to models of the theory. I will describe the results and outline our current research problems.

seminar begins with tea.