# Model theory of difference fields, part II

## Alice Medvedev

### City College -- CUNY

This talk is a continuation of last week’s Logic Workshop. The necessary background will be summarized briefly at the beginning of this talk.

**ACFA**, the theory of difference closed fields, is a rich source of explicit examples of forking independence and nonorthogonality, the distinction between stable and simple theories, and the distinction between one-based and locally-modular groups. To present these examples, I will introduce “difference varieties”, which are the basic building blocks of definable sets in **ACFA**, and “sigma-varieties”, a more tractable special case of these.

Prof. Medvedev is a model theorist, teaching at City College in the CUNY system. She received her doctorate from the University of California-Berkeley, under the supervision of Tom Scanlon, and subsequently held postdoctoral positions at Berkeley and at the University of Illinois-Chicago.