Usually I give talks at the blackboard with no slides, so typically I have no materials to distribute. Occasionally, however, there are some.

Slides from a (very old) 2000 talk about toric varieties and modular forms.

2003 TWIGS talk about modular forms. This was an introductory lecture for our graduate students about modular forms and their applications.

2003 TWIGS talk about stratified spaces. This was an introductory lecture for our graduate students about stratified spaces, with some examples.

Slides from a lecture on crytography I gave at the UMass 2004 Mathematics Contest Banquet. A brief introduction to the mathematics behind public-key cryptography

A lecture to the 2004 PROMYS program about the ABC conjecture. This talk was for advanced high-school students, and discussed certain Diophantine equations and the analogy between integers and complex polynomials in one variable.

Here are some tips for graduate students who think they might want to write a dissertation under Bob MacPherson. These were delivered as part of a roast at the banquet at his 60th birthday celebration conference, held at IAS in the fall of 2004.

A talk about Weyl group multiple Dirichlet series given at Maryland in Fall 2006.

A talk about the cohomology of congruence subgroups of SL(4,Z) delivered at the RIMS conference Automorphic representations, automorphic L-functions and arithmetic held in Winter 2009.

A talk about testing a modularity conjecture for elliptic curves over the field of fifth roots of unity, given at the 2009 Oberwolfach meeting Explicit methods in number theory.

A talk about computing Hecke operators and cohomology given at the 2009 GTEM meeting in Warwick (UK).

Some illustrations that accompanied a lecture to the 2010 PROMYS program about expander graphs.

A talk about Kazhdan–Lusztig cells showing that affine cells are regular (meaning the set of reduced expressions of the elements of a KL cell is a regular language in the sense of formal language theory). From a 2010 AMS meeting in Hoboken.

A talk about Weyl group multiple Dirichlet series given at the workshop

*Durham Days on Modular Forms*, Durham (UK), Summer 2010.A talk about computationally investigating modularity of elliptic curves over number fields given at a birthday conference in honor of Jeff Hoffstein, Thessaloniki (GR), 2014. Includes multiple pictures of pugs celebrating their birthdays (apparently this was an internet thing) and the only time I attempted a meme.

A talk about computing Hecke operators on Sp(4) given at

*Explicit methods in number theory*in Oberwolfach in 2018. Joint work with Mathieu Dutour Sikiric.Slides to accompany a talk about the growth of torsion in the cohomology of arithmetic groups. Given at the Clay Research Workshop

*Patterns in cohomology of moduli spaces*, Oxford (UK), Fall 2019. These might not make any sense without the context of the talk, but at least one can look at them. Also the slides don’t say it, but this is joint work with Avner Ash, Mark McConnell, and Dan Yasaki.