Wed, 08 Jun 2016

16:00 - 17:00
C1

Finiteness properties of subgroups of direct products of surface groups

Claudio Llosa Isenrich
(Oxford)
Abstract

We will explain a result of Bridson, Howie, Miller and Short on the finiteness properties of subgroups of direct products of surface groups. More precisely, we will show that a subgroup of a direct product of n surface groups is of finiteness type $FP_n$ if and only if there is virtually a direct product of at most n finitely generated surface groups. All relevant notions will be explained in the talk.

 

Wed, 01 Jun 2016

16:00 - 17:00
C1

Finding CAT(-1) structures on groups

Sam Brown
(UCL London)
Abstract

I will describe a method to find negatively curved structures on some groups, by manipulating metrics on piecewise hyperbolic complexes. As an example, I will prove that hyperbolic limit groups are CAT(-1).

Wed, 25 May 2016

16:00 - 17:00
C1

Simplicial Boundary of CAT(0) Cube Complexes

Kobert Ropholler
(Oxford)
Abstract

The simplicial boundary is another way to study the boundary of CAT(0) cube complexes. I will define this boundary introducing the relevant terminology from CAT(0) cube complexes along the way. There will be many examples and many pictures, hopefully to help understanding but also to improve my (not so great) drawing skills. 

Wed, 18 May 2016

16:00 - 17:00
C1

Residual properties of amalgams

Gareth Wilkes
Abstract

I will discuss the circumstances in which residual finiteness properties of an amalgamated free product $A\ast_c B$ may be deduced from the properties of $A$ and $B$, with particular regard to the pro-p residual properties.

Tue, 17 May 2016

10:00 - 11:00
C1

Number theory tools for Cryptographic Applications

Giacomo Micheli
(Oxford University)
Abstract

In this lecture we describe the effective Chebotarev Theorem for global function fields and show how this can be used to describe the statistics of a polynomial map f in terms of its monodromy groups. With this tool in hand, we will provide a strategy to remove the remaining heuristic in the quasi-polynomial time algorithm for discrete
logarithm problems over finite fields of small characteristic.

Wed, 11 May 2016

16:00 - 17:00
C1

Commutator Subgroup and Quasimorphisms

Nicolaus Heuer
(Oxford)
Abstract

Quasimorphisms (QM) of groups to the reals are well studied and are linked to stable commutator length (scl) via Bavard Duality- Theorem. The notion of QM can be generalized to yield maps  between groups such that each QM from one group pulls back to a QM in the other.

We will give both a short overview of features of scl and investigate these generalized QMs with large scale properties of the commutator group. 

Wed, 04 May 2016

16:00 - 17:00
C1

Classifying Groups up to Quasi-Isometry

Alex Margolis
Abstract

In his ICM address in 1983, Gromov proposed a program of classifying finitely generated groups up to quasi-isometry. One way of approaching this is by breaking a group down into simpler parts by means of a JSJ decomposition. I will give a survey of various JSJ theories and related quasi-isometric rigidity results, including recent work by Cashen and Martin.

Wed, 27 Apr 2016

16:00 - 17:00
C1

Random walks, harmonic functions and Poisson boundary

Vigolo Federico
(Oxford)
Abstract

in this talk I will try to introduce some key ideas and concepts about random walks on discrete spaces, with special interest on random walks on Cayley graphs.

Mon, 29 Feb 2016
16:30
C1

Torelli and Borel-Tits theorems via trichotomy

Carlos Alfonso Ruiz Guido
(Oxford University)
Abstract

Using the "trichotomy principle" by Boris Zilber I will give model theoretic proofs of appropriate versions of Torelli theorem and Borel-Tits theorem. The first one has interesting applications to anabelian geometry, I won't assume any prior knowledge in model theory.

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