CCNY Lecture Series :


Title: More on proofs

DR. George Havas
ARC Centre for Complex Systems and Centre for Discrete Mathematics
and Computing School of Information Technology and Electrical Engineering

The University of Queensland

Date: Tuesday, February 21, 2006
Time: 12:30 PM
Room: The CS Conference Room, NAC 8/205

Abstract

Given a finite presentation of a group $G$, proving properties of $G$ can be difficult. Indeed, many questions about finitely presented groups are unsolvable in general. Algorithms exist for answering some questions while for other questions algorithms exist for verifying the truth of positive answers. An important tool in this regard is the Todd-Coxeter coset enumeration procedure. It is possible to extract formal proofs from the internal working of coset enumerations. We give examples of how this works, and show how the proofs produced can be mechanically verified and how they can be converted to alternative forms. We discuss these automatically produced proofs in terms of their size and the insights they offer. We compare them to hand proofs and to the simplest possible proofs. We point out that this technique has been used to help solve a longstanding conjecture about an infinite class of finitely presented groups.