On Families of Filtered phi Modules and Crystalline Representations

Eugen Hellmann
University of Bonn
December 8, 2010

We study families of filtered phi-modules associated to families of p-adic Galois representations as considered by Berger and Colmez. We show that the weakly admissible locus in a family of filtered phi-modules is open and that the groupoid of weakly admissible modules is in fact an Artin stack. Working in the category of adic spaces instead of the category of rigid analytic spaces one can show that there is an open substack of the weakly admissible locus over which the filtered phi-modules is induced from a family of crystalline representations.

Introduction to the Coq Proof Assistant

Andrew Appel
Princeton University
December 7, 2010

A "proof assistant" is a software package comprising a validity checker for proofs in a particular logic, accompanied by semi-decision procedures called "tactics" that assist the mathematician in filling in the easy parts of the proofs. I will demonstrate the use of the Coq proof assistant in doing simple proofs about inductive structures such as natural numbers, sequences, and trees.

Constructive Type Theory and Homotopy

Steve Awodey
Institute for Advanced Study
December 3, 2010

In recent research it has become clear that there are fascinating connections between constructive mathematics, especially as formulated in the type theory of Martin-Löf, and homotopy theory, especially in the modern treatment in terms of Quillen model categories and higher-dimensional categories. This talk will survey some of these developments.

A Reidemeister-Singer Conjecture for Surface Diagrams

Jonathan Williams
University of California, Berkeley
December 3, 2010

There is a way to specify any smooth, closed oriented four-manifold using a surface decorated with simple closed curves, something I call a surface diagram. In this talk I will describe three moves on these objects, two of which are reminiscent of Heegaard diagrams for three-manifolds. These may form part of a uniqueness theorem for such diagrams that is likely to be useful for understanding Floer theories for non-symplectic four-manifolds.