# Faculty News Briefs

### May 2008

On April 2, 2008 Professor Tom Braden gave a talk in the *Topology et. al.* seminar at Wesleyan University entitled *Toric and Hypertoric Varieties: Topology and Combinatorics.*

On April 5, 2008 Professor Eduardo Cattani gave a talk on *Rational Hypergeometric Functions in Two Variables* at the Special Session on D-Modules of the AMS Sectional Meeting in Bloomington, Indiana. He also attended the Workshop on Hodge Theory at the Banff International Research Station (BIRS) in Banff, Canada during the period April 6ñ11. A co-organizer of this workshop was Greg Pearlstein, who received his Ph.D. in our department in 1999 under the direction of Professor Aroldo Kaplan.

Professor Paul Gunnells attended the workshop Computing Arithmetic Spectra, held March 10ñ14, 2008 at the American Institute of Mathematics in Palo Alto, California.

During March and early April 2008, Professor Rob Kusner visited TU-Berlin and TU-Darmstadt in Germany, ETH in Zurich, Switzerland, and University of Milan in Italy. He pitched a season-opening double-header (and now has a 2.718281828... ERA) in the Augsburg-Darmstadt-Frankfurt-Heidelberg-Mannheim Geometric Analysis Oberseminar on April 11 on the topic of *Holomorphic Differentials and Surface Theory.* The first game was against an old combinatorial geometric problem of triangulating tori; using sextic differentials and Abelís Theorem, one can give a quick proof that there are no such triangulations with exactly one 5-fold and one 7-fold vertex. The second opponent was the classification of complex projective structures (which, via the Schwarzian, amount to the space of quadratic differentials with polynomial growth) on C and applications of this to the moduli space of constant mean curvature surfaces; in fact, a consequence of this approach is a slick *holomorphic* proof of Stasheffís theorem about the associahedron being a cell. Earlier that week in Milan, Rob pitched a special morning game against *Knotted Ropes and Bands,* and he faced the same rival again in the joint Bryn Mawr-Haverford Colloquium on April 28. Ball four!

Professor Michael Lavine gave a talk on April 2, 2008 at the University of Connecticut and a talk on April 10 at Boston University. Both talks were entitled *The Multiset Sampler, a New MCMC Algorithm.*

Visiting Assistant Professor Ralf Schiffler gave a talk at the International Conference on Representation Theory of Algebras and Related Topics, which took place at Woods Hole during the period April 25ñ27, 2008. The title of his talk was *Cluster-Tilted Algebras and Slices.*

Professor John Staudenmayer has been invited to become an associate editor of Biometrics, a applied statistics journal that is the premier publication of the International Biometrics Society.

During April 2008 Professor Jenia Tevelev gave a talk entitled *Hypergraph Curves, Divisors, and Morphisms* at the Commutative Algebra and Algebraic Geometry Seminar at the University of California Berkeley and a talk entitled *Tropical Compactifications* at the Toric Varieties Seminar at the University of California Berkeley and at the Geometry-Algebra-Singularities-Combinatorics Seminar at Northeastern University.

On April 26ñ27, 2008 Emeritus Professor Floyd Williams was one of six speakers in the Workshop on Lie Groups, Lie Algebras, and their Representations, held at the University of California at Santa Cruz. His one-hour talk was entitled *Zeta Integrals on Higher Rank Symmetric Spaces.* Among the other speakers was Zongzhu Lin, who received his Ph.D. in our department in 1989 under the direction of Professor Jim Humphreys. Now a professor at Kansas State University, Zongzhu Lin gave a talk entitled *Frobenius Twisted Conjugacy Classes In Full Matrix Rings.*

### April 2008

On March 16, 2008 Professor Tom Braden gave a talk at the AMS meeting at New York University in a special session on algebraic combinatorial geometry. The talk was entitled *Hypertoric Varieties and Gale Duality.*

Professor Emeritus Ed Connors was appointed to a 3-year term on the Karl Menger Prize Committee. The committee will serve as the American Mathematical Society's special awards judges at this yearís Intel International Science and Engineering Fair being held in Atlanta during the period May 11ñ16, 2008.

A new book by Professor Emeritus Jim Humphreys will be published by the American Mathematical Society later this year in their series Graduate Studies in Mathematics. The title is Representations of Semisimple Lie Algebras in the BGG Category O; the upper case script letter O comes from the Russian word *osnovnoj* meaning basic or principal. BGG abbreviates the names of Joseph Bernstein, Israel Gelfand, and Sergei Gelfand.

Professors Rob Kusner and Franz Pedit and their former Ph.D. students Martin Kilian, Wayne Rossman, and Nick Schmitt, participated in a week-long meeting at Kloster Schˆntal in Germany's Odenwald during the first week of March 2008. Kilian, now a professor in Cork, Ireland, reported on his recent breakthrough on the Lawson conjecture, asserting that the Clifford torus is the only embedded minimal surface of genus 1 in the three-sphere. Rossman and Schmitt, now professors in Kobe, Japan, and T¸bingen, Germany, respectively, helped the attendees celebrate the 48th birthday of their former advisor at the meeting. As is well known, 48 is the order of the symmetry group for the cube, and so, in order to honor the occasion, Rob was given a small but perfect cubic crystal of sodium chloride.

### March 2008

On January 31, 2008 Visiting Assistant Professor Roman Fedorov gave a talk at the Boston University Geometry Seminar. The title was *Langlandís Transform and PainlevÈ Equations.*

During the week of February 18ñ25, 2008, Professor Rob Kusner visited the University of Georgia in Athens, where he collaborated and lectured on constant mean curvature surfaces.

Professor William Meeks is on sabbatical during the spring semester of 2008. As part of his sabbatical he is traveling overseas to give talks and to do joint research projects. At the beginning of the year he spent one month in Spain at the University of Granada to do joint research with Professors Ferrer and Martin and with Professors Perez and Ros. While there he solved one well known conjecture together with Perez and Ros called the *Stable Limit Leaf Conjecture.* In less than a month, Professor Meeks wrote up the paper, submitted it to the Journal of Differential Geometry for review, and the journal accepted it for publication. While there, he also gave a talk in the geometry seminar. He plans to return to Granada in March for about one month and then again at the end of May for about a month. During his May visit to Europe he will attend a geometry conference in Rome. Professor Meeks also reports on the following invitations.

In March he will be going to McGill University in Montreal in order to lecture on his recent paper, *Dynamics Theorem for CMC Surfaces,* which is based on joint research with Giuseppe Tinaglia.

At the beginning of May, he plans to attend and give a plenary talk at the Triannual Journal of Geometry Conference at Harvard University. He will then leave for a two-week visit to Korea, where he will give a series of eight research talks to geometers.

At the end of August, he will give a plenary talk at a conference on geometry and physics at Harvard University as part of the 60th birthday celebration in honor of his friend, Professor S.T. Yau of Harvard University.

Finally, in November he will be giving two plenary lectures on his research at the annual *Current Developments in Mathematics Conference* at MIT-Harvard. His invitation is considered to be a special honor. The speakers invited to this conference will speak on the most interesting recent developments in mathematics.

On February 15, 2008 Visiting Assistant Professor Ralf Schiffler gave a talk at the Colloquium on Modules and Related Topics at the UniversitÈ du QuÈbec ‡ MontrÈal. The title of his talk was *Sur la Structure Combinatoire des AlgÈbres AmassÈes.*

A paper entitled *Density Estimation in the Presence of Heteroskedastic Measurement Error* by Professors John Staudenmayer, John Buonaccorsi, and David Ruppert of Cornell University is to appear in the Journal of the American Statistical Association.

### February 2008

Professor John Buonaccorsi was a guest researcher at the Section for Biostatistics at the University of Oslo Medical School for much of January 2008, with support provided by the Norwegian Research Council. He continued his ongoing collaboration with colleagues on statistical methods for handling measurement error and misclassification in epidemiologic studies. He also presented a talk on *Measurement Error in Time Series with Applications to Population Dynamics* through the Centre for Research-based Statistical Innovation at the University of Oslo.

Professor Panos Kevrekidis has published his first book, which appeared in Springer-Verlagís Atomic, Optical, and Plasma Series. Co-edited by Panosís close collaborators Dimitri Frantzeskakis and Ricardo Carretero-Gonz·lez, the book is entitled Emergent Nonlinear Phenomena in Bose-Einstein Condensates. The book features a series of theoretical and experimental review-style chapters by experts on different nonlinear phenomena arising in the field of Bose-Einstein Condensates, which is a major thrust of Panosís work. The preface was written by Professor Wolfgang Ketterle of MIT, who won the Nobel Prize.

During January 2008 Professor Rob Kusner lectured on *Nondegeneracy of Constant Mean Curvature Surfaces* at the University of Pennsylvania, where he is spending his sabbatical this spring. Robís collaborator and former NSF postdoctoral fellow at UMass, Jason Cantarella (also on sabbatical at Penn now), also spoke about their joint work *Minimizing the Length of Curves with Curvature Bounded Above.*

### January 2008

We are happy to welcome Professor Michael Lavine to our department. His official starting date is January 27, 2008.

Visiting Assistant Professor Ralf Schiffler gave a colloquium talk at Kansas State University on December 3, 2007. The title of his talk was *Quiver Representations: Basic Facts and Some Recent Developments.*

During December 2007 Professor Jenia Tevelev gave talks at the Algebra, Geometry, and Physics Seminar at SUNY Stony Brook and at the Tropical Geometry Workshop in Oberwolfach, Germany. The talks were entitled *Tropical Compactifications of Subvarieties of Tori.* Jenia was also appointed an editor of the journal Transformation Groups.