**Date & Time:** Wednesday, January 07, 2015, 16:00-17:00.

**Venue:** Ramanujan Hall

**Speaker:** S. M. Srivastava, ISI Kolkota

**Title:** Ultraproduct of models and an application to algebra

**Abstract:** In this talk we shall introduce the notion of ultraproduct of models. This is a very useful notion of product of algebraic structures that should be better known to mainstream mathematicians. As an application we shall briefly sketch the proof of Ax-Kochen theorem on the field Q_p of p-adic reals.

We shall completely define all the necessary notion from logic. However, some background in algebra, particularly in valuation theory, will be assumed.