Most of these links (which appear more or less in reverse chronological order) are for slide presentations from a laptop, although in a few cases I have a screen-and-audio-capture.
In May 2014 I gave a talk called Homomesy: actions and averages at the U. Washington Combinatorics Seminar. Earlier versions of this talk include one called Combinatorial ergodicity: actions and averages that I gave in February 2013 at the MIT Combinatorics Seminar (though I am moving away from using the term "combinatorial ergodicity"; "combinatorial homomesy" might have been better).
In April 2014 I gave a talk called Math, Magic, and Mystery at the University of Connecticut math department's awards ceremony. A video of the talk is available via my media webpage.
In February 2014 I presented a problem called Ehrhart theory plus cylic sieving at the Cambridge Combinatorics Coffee Club.
In May 2013 I gave a talk for newly-inducted members of the UMass Lowell chapter of Pi Mu Epsilon (the national mathematical honor society) titled Bridging the gap between the continuous and the discrete.
In November 2012 I presented a talk entitled Quasirandom processes at Dartmouth; this was fairly similar to other talks of the same name I gave at the Connecticut Valley Colloquium in November 2011 and the Pacific Institute of Mathematics in May 2010.
In September 2012 I gave a talk entitled Rotor-routing, smoothing kernels, and reduction of variance: breaking the O(1/n) barrier. This was similar to talks of the same title that I gave at UC Davis in March 2012, MSRI in January 2012, and MIT in October 2011.
In August 2012 I gave a talk on Growth, Erosion, and Competition Driven by Random and Non-Random Walk at the 2012 MathFest.
In August 2012 I gave a talk on Walks on Walks at the 2012 MathFest. (This was related to the talk on combinatorial ergodicity I'd just given at Berkeley a few months earlier.)
In May 2012 I gave a lecture on Negative Numbers in Combinatorics: Geometrical and Algebraic Perspectives for the MSRI-Up program.
In April 2012 I gave a lecture to the public as the kick-off for an evening at MSRI that I organized, entitled Wild Beauty: Postcards from Mathematical Worlds.
In April 2012 I gave a talk on De-randomizing randomness with rotor-routers for the Berkeley Mathematics Circle.
In April 2012 I gave a talk on Combinatorial Ergodicity at the UC Berkeley combinatorics seminar.
In April 2012 I gave a lecture on Rotor-Router Walk in Two Dimensions for the Combinatorics and Stochastic Processes Seminar at UC Berkeley organized by Doug Rizzolo.
In March 2012 I gave a talk entitled Bugs, Blobs, and Rotor-Routers: What happens to probability theory when you get rid of randomness? for the winners of the Bay Area Mathematical Olympiad and their families.
In February 2012, at the Tenth International Conference on Monte Carlo and Quasi-Monte Carlo Methods in Scientific Computing, I presented a talks entitled Reducing variance with averaging kernels: General theory and an application to quasirandom simulation of Markov chains.
In January 2012 I presented a talk on A not-quite-bijective enumeration of domino tilings of Aztec diamonds at the Joint Mathematical Meetings, as part of a session on Clever Counting or Beautiful Bijection?.
In April 2011 I gave a talk called Why random tilings don't look random at a meeting at Northeastern held in honor of Anatoly Vershik.
In April 2011 I gave a short talk on Farey-ish fractions from weighted mediants at the Cambridge Combinatorics Coffee Club. Since then, PRIMES student Dhroova Aiylam has made progress on these problems.
In spring 2011 I gave a talk entitled How well can you see the slope of a digital line? (and other applications of averaging kernels). It was a slight variant of an earlier talk with a slightly different title: How well can you see the slope of a digital line? (and other applications of non-uniform averaging). (One was given at UMass Lowell, the other at UMass Boston.) For those with access to Mathematica, a Mathematica version of the talk is available.)
In January 2011 I gave a talk on Self-organizing structures in rotor-router blobs at the Joint Mathematical Meetings.
In October 2010 I gave a short talk on Rotor-router types at the Cambridge Combinatorics Coffee Club. Since then, PRIMES student Xiaoyu He has made progress on these problems.
In April 2010 I presented a talk on Local-to-Global Phenomena for Rotor-Routing (describing joint work with Giuliano Giacaglia, Lionel Levine, and Linda Zayas-Palmer, now published and also available via the arXiv) at the MIT Combinatorics Seminar.
In spring 2010 I presented a talk called Rotor walks and Markov chains at the UC Berkeley probability seminar. This talk was based on my article of the same name, co-authored with Alexander Holroyd; one earlier version of the talk was given in the MIT Probability Seminar and the another at a workshop entitled New Directions in Random Spatial Processes.
In spring 2010, my student Linda Zayas-Palmer delivered a talk I wrote at the ninth Gathering for Gardner; it was entitled Why 0.999... is greater than 1.000..., and is related to my hopes of using ideas from the theory of chip-firing on infinite graphs to give some new-ish constructions of the real numbers. (I say "new-ish" because these constructions are best seen as a slight generalization of the construction of Falton, Metropolis, Rota and Stein; see Darryl McCullough's talk A sample of Rota's mathematics.)
In March 2010, I gave a talk entitled Dedekind's forgotten axiom and why we should teach it (and why we shouldn't teach mathematical induction in our calculus classes) at the 2010 annual meeting of the History and Pedagogy of Mathematics Americas section
In April 2009, I gave a talk entitled Tiling lattices with sublattices at the Northeastern Sectional Meeting of the American Mathematical Society.
In November 2008, I gave a talk entitled Derandomized random walk in one and two dimensions in the MIT Combinatorics Seminar. The preceding link is for the outline; you can also view a screen and audio capture of the lecture that includes graphics.
In July 2008, at the Eighth International Conference on Monte Carlo and Quasi-Monte Carlo Methods in Scientific Computing, I presented two talks, entitled The rotor-router mechanism for quasirandom walk and aggregation and Derandomized parallel simulation of Markov chains via P-machines.
In March 2008, at the Eighth Gathering for Gardner, I presented a short talk entitled Pi over Eight by Way of Infinity.
In March 2008, I presented a talk entitled Quasirandomness via rotor-routers at CCR - La Jolla.
In December 2007, I presented a talk entitled Chip-firing groups and fractal structures arising from graph-Laplacians at the Geometric Group Theory and Topology seminar at Tufts University
In June 2007, I presented a talk entitled A whirling tour of chip-firing and rotor-routing at a DIMACS workshop held in honor of Peter Winkler. (At this workshop I also sponsored a limerick contest in honor of Pete.)
In March, 2005 I gave a talk at the Harvard Statistics Department seminar, entitled Better than random: Quasirandomness for discrete stochastic systems. This is one in a series of talks with a good deal of overlap, such as the talk I gave at Northeastern University in January of 2006, entitled Random walk and random aggregation, derandomized, or the talk I gave at the University of Memphis in March of 2006 (as part of the 2006 Erdos Conference), entitled Discrete quasirandomness: questions and applications. (I've also given versions of this talk to undergraduates; see for instance the talk Better than random: a hands-on introduction to quasirandomness I presented to the Pi Mu Epsilon Society of U. Mass. Lowell in April 2007.)
In January, 2005 I gave a talk at the Joint Winter Meetings entitled "Gale-Robinson sequences and the cube and octahedron recurrences". I've put the abstract and slides on-line.
In April of 2005, I gave a talk in honor of Richard Brualdi entitled "Symbiosis and Reciprocity", for which slides are available. (For more on reciprocity see the talk I gave in honor of Richard Stanley in June of 2004, described below.)
In 2005, I gave a talk (at MIT, Northeastern University, the University of Washington, Microsoft Research, and Brown University) entitled "The combinatorics of Markoff numbers". The abstract and slides are available. There is also a shorter version of the talk, which was presented at the Formal Power Series and Algebraic Combinatorics (FPSAC) conference held in San Diego in 2006 (an extended abstract for that talk is also available).
In January, 2005 I gave a talk at the Boston University Dynamical Systems Seminar entitled "Rational maps, Laurent polynomials, and combinatorics". This (mostly) subsumes the talks "Laurent polynomials, dynamics, and combinatorics" and "When algebraic entropy vanishes" described below. I've put the abstract and slides on-line.
In November of 2004, I gave a talk at the University of Maryland entitled "When algebraic entropy vanishes". This talk examined algebraic recurrences in general, and the Laurent phenomenon in particular, from a dynamical-systems point of view. This was more or less a repeat of the talk by the same name that I gave at the Tufts University dynamics seminar in October of 2003.
In Fall 2004 I gave three lectures at U.C. Berkeley, discussing quasirandomness in greater detail. Click here for more information.
In June of 2004, I gave a talk at the Stanley Fest held in honor of Richard Stanley's 60th birthday; my talk was entitled "Richard Stanley and combinatorial reciprocity", and the slides are available on the web. (For more on reciprocity see the talk I gave in honor of Richard Brualdi in April of 2005, described above.)
In 2003 I gave a lecture at Microsoft Laboratories on quasi-random walk and aggregation models; the video is available on the web, and has links to other information on the topic. If that link doesn't work, try this one.
In June of 2003, I gave a talk at the IDA-sponsored symposium Alternating Sign Matrices: A Conference in Honor of David Robbins. My talk was entitled "The many faces of alternating-sign matrices". You can view the slides for my talk while listening to the audio recording kindly made by Clara Chan and the folks at IDA. (I've also written an article with the same name as the talk, covering much of the same material, published in July 2001 in "Discrete Models: Combinatorics, Computation, and Geometry", a special issue of Discrete Mathematics and Theoretical Computer Science.)
In March of 2003, I gave a talk at the Number Theory and Combinatorics in Physics Conference. My talk was entitled "q versus lambda: plane partitions, alternating sign matrices, and lattice models", and you can read the abstract or see the slides.
In November of 2002, I gave a talk at the Fellowship of the Ring seminar at Brandeis University, entitled "Laurent polynomials, dynamics, and combinatorics". The slides for this talk are somewhat similar to the slides for the talk I gave in July of 2002 (see next item), but geared towards algebraists rather than specialists in discrete models and statistical mechanics. Both talks were precursors to the talk I gave at Tufts in Fall 2003 (see above).
In July of 2002, I gave a talk at the Workshop on Combinatorics and Integrable Models held in Canberra (via phone-link, from the comfort of my kitchen table). Here are the slides from my talk. (If there's interest, I could transcribe and/or digitize the words I spoke that accompanied the transparencies, and put the transcript and/or audiofile up on the Web.)
You can check out the slides that were used in my talk Diabolo Tilings of Fortresses (presented in the MIT Combinatorics Seminar on 5/13/98). You'll need to gunzip the file and view it with gs (not ghostview) or print it out.
In 1997, I presented a talk at the AMS/MAA Joint Winter Meetings, giving a simplified proof of the main result of my 1992 paper Alternating-Sign Matrices and Domino Tilings (written with Elkies, Kuperberg, and Larsen). I've put the slides on-line.