# Tour dates

In A-infinity, Conferencing, Mathematics, PhD, Topology, Travel.

*Edited to add Galway*

I'll be doing a "US tour" in March / April. For the people who might be interested - here are my whereabouts, and my speaking engagements.

I'm booked at several different seminars to do the following:

For a ring R, the Ext algebra [tex]Ext_R^*(k,k)[/tex] carries rich information about the ring and its module category. The algebra [tex]Ext_R^*(k,k)[/tex] is a finitely presented k-algebra for most nice enough rings. Computation of this ring is done by constructing a projective resolution P of k and either constructing the complex [tex]Hom(P_n,k)[/tex] or equivalently constructing the complex [tex]Hom(P,P)[/tex]. By diligent choice of computational route, the computation can be framed as essentially computing the homology of the differential graded algebra [tex]Hom(P,P)[/tex].

Being the homology of a dg-algebra, [tex]Ext_R^*(k,k)[/tex] has an induced A-infinity structure. This structure, has been shown by Keller and by Lu-Palmieri-Wu-Zhang, can be used to reconstruct R from[tex]Ext_R^{\leq 2}(k,k)[/tex].In this talk, we shall discuss the computation of [tex]Ext_R^*(k,k)[/tex] and methods for computing an A-infinity structure on the Ext algebra. Examples will be drawn from group cohomology, where the computation of the Ext algebra has conditions from Benson and Carlson for recognizing whether a partial computation has the entire structure.

I will be in Millersville, with occasional visits to UPenn during March 25-28 and April 10-20. I'll be somewhere in Illinois most of March 28, and at UIUC for the GSTC 29-30. I'll be at MSRI March 31-April 4, and then at Stanford April 4-10.