# Faculty News Briefs

### 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.

### December 2007

On November 26, 2007, Professor Tom Braden gave a talk entitled *Category O for Hyperplane Arrangements* in the Geometry, Algebra, Singularities, and Combinatorics Seminar at Northeastern University.

During November, Visiting Assistant Professor Roman Fedorov gave a talk entitled "Deformations of Algebro-Geometric Solutions of KadomtsevñPetviashvili Equations and Frobenius Manifolds at the joint Math-Physics Seminar at the University of Pennsylvania.

During the period November 18ñ20, 2007, Professor Hans Johnston attended the Division of Fluid Dynamics meeting of the 60th annual American Physical Society meeting in Salt Lake City. At the meeting he participated in the following three activities: he gave a talk entitled *A Spectral Collocation Method for 2D Incompressible Fluids in Vorticity Formulation*; along with Charles Doering, he contributed a video to the Video Gallery of Fluid Motion entitled *Rayleigh-Benard Convection with Imposed Heat Flux*; he chaired a session entitled *Computational Fluid Dynamics.* His talk was presented at this session.

Professor Panos Kevrekidis had a busy fall. During October, Panos gave the Mathematics Colloquium at the University of Vermont on October 4, and then in the third week of October, he was one of the invited speakers at the workshop on Hamiltonian Lattice Dynamical Systems, which took place in Leiden, Netherlands. Panos was also invited to be a Visiting Fellow at the Research Excellence Centre on Optical Communications and Quantum Atom Optics at the Australian National University in Canberra, Australia, where he spent two weeks and presented an invited seminar. Finally, Panos was recently awarded a Humboldt Research Fellowship and will be spending his sabbatical from March to July 2008 at the University of Heidelberg in Germany.

On November 19, 2007, Visiting Assistant Professor Ralf Schiffler gave a talk entitled *Cluster-tilted Algebras* in the Geometry, Algebra, Singularities, and Combinatorics seminar at Northeastern University.

On November 7, 2007 Professor Jenia Tevelev gave a talk entitled *Tropical Compactifications of Subvarieties of Tori* in the Algebraic Geometry Seminar at the University of Michigan. On November 16 he gave a talk entitled "Elimination Theory for Tropical Varieties" in the Mathematics Colloquium at Cleveland State University.

### November 2007

On October 7, 2007 Professor Tom Braden gave a talk in a special session on toric varieties at the fall meeting of the American Mathematical Society, which was held at Rutgers University in New Brunswick, NJ. The talk was entitled *A Ring Structure on Intersection Cohomology of Hypertoric Varieties.*

Professor Erin Conlon gave a talk at the Third Annual Geobacter meeting, which was held in Amherst, Massachusetts on October 22, 2007. The title of her talk was *Geobacter Sulfurreducens Transcription Factor Binding Site Discovery.*

Professor Brian Emond presented a paper at the E-Learn 2007 World Conference on E-Learning in Corporate, Government, Healthcare and Higher Education, which was held in Quebec City, Quebec, Canada during the period Qctober 15ñ19. The paper was entitled *Using an Online-Supported Text Homework System in Undergraduate Precalculus Classes: A Pilot Study.* The paper reports on the preliminary results of student performance in the new precalculus curriculum and the on-line student support system that instructors are using at UMass Amherst. He also received a second grant from the Center for Teaching for the training of precalculus instructors on the use of the system.

Professor Paul Gunnells spoke about Weyl group multiple Dirichlet series at both the Explicit Methods in Number Theory meeting in Oberwolfach, Germany (July 15ñ21, 2007) and the Maine/Quebec Conference on Number Theory and Related Topics at the University of Maine (September 29ñ30, 2007). He also participated in the Workshop on L-functions and Modular Forms, which took place at the American Institute of Mathematics in Palo Alto, CA, from July 30 to August 3, 2007. Professor Gunnells was a co-organizer of the five-day workshop on Low-dimensional Topology and Number Theory, which took place at the Banff International Research Station in Banff, Alberta during the period October 21ñ26.

The Aspen Center for Physics (http://www.aspenphys.org/) has invited Professor Rob Kusner and his UMass Physics colleague Chris Santangelo to lead a workshop on the Geometry of Condensed Matter (http://people.umass.edu/csantang/geometry.html) during June and July

2008.

Visiting Assistant Professor Ralf Schiffler gave a talk at the International Conference on Representations of Algebras and Related Topics, which was held at Northeastern University during the period October 5ñ7, 2007. His talk was entitled *A Cluster Expansion Formula.* He also gave a talk at the International Meeting on Representation Theory of Algebras, which took place in Sherbrooke, Canada during the period October 12ñ14. The title of his talk was "Cluster-tilted Algebras.

During the second week of October Professor Eric Sommers co-organized a workshop at INDAM in Rome, Italy with Professor Paolo Papi of the University of Rome (La Sapienza). The title of the workshop was B-stable Ideals and Nilpotent Orbits. Among the twenty talks, graduate student Molly Fenn presented her thesis work in a talk entitled *Equivalence Classes of B-stable Ideals,* and Professor Sommers gave a talk entitled *Minimal Points in Cells.*

On October 10, 2007 Professor John Staudenmayer gave a talk in the Department of Biostatistics at Johns Hopkins University. The title of the talk was *Density Estimation in the Presence of Heteroscedastic Measurement Error.*

Professor Emeritus Floyd Williams was one of six invited speakers at the Workshop on Lie Groups, Lie Algebras, and Their Representations, which was held at the University of California Berkeley during the period October 27ñ28, 2007. The workshop was organized by Professor Joseph Wolf. Professor Williamsís talk was entitled *Harmonic Analysis on a Hyperbolic Cylinder.*

### October 2007

Professor John Buonaccorsi was an invited presenter/participant at the National Institute on Aging Workshop on Statistical Methods for Longitudinal Data on Aging held in Bethesda, MD on June 13ñ14, 2007. John gave a talk at the workshop entitled *Measurement Error in Longitudinal Studies.*

Professor Rob Kusner lectured on *Nondegeneracy for CMC Surfaces* at the Korea Institute for Advanced Study conference on Geometric Analysis (September 7ñ11, 2007) and at the conference celebrating the 60th birthdays of Professor Bill Meeks and former UMass Professor David Hoffman in Buzios, Brasil (August 20ñ25, 2007). Between these two conferences, Rob was a member of IMPA in Rio de Janiero, where he and collaborator Karsten Grosse-Brauckmann wrote a new paper on conjugate Plateau construction of minimal surfaces in the Heisenberg group Nil(3) and CMC surfaces in H^2 x R, two of the eight *Thurston geometries* on 3-manifolds.

Professor Andrea Nahmod is giving a minicourse at the NSF-sponsored 10th New Mexico Analysis Seminar held in Albuquerque on October 11ñ12, 2007. The title of her minicourse is *Bilinear Operators in Analysis and PDEs.* Full details are available at the URL http://www.math.unm.edu/conferences/10thAnalysis/.

### September 2007

On June 19, 2007 Professor Tom Braden gave a talk entitled *Hyperplane Arrangements and Hypertoric Varieties* at a workshop on combinatorics and topology held at the Institute for Advanced Studies, Hebrew University in Jerusalem. He was also awarded a two-year NSA grant totaling $61,120 for a project entitled *Equivariant Topology of Singular Varieties.*†

Professor John Buonaccorsi gave an invited talk entitled *Measurement Error/Errors-in-variables in Longitudinal Models* at a special National Institute on Aging Workshop on Statistical Methods for Longitudinal Data on Aging. The workshop was held in Bethesda, MD during the period June 13--14, 2007.

Professor Richard S. Ellis was a member of the International Advisory Committee for the workshop on Dynamics and Thermodynamics of Systems with Long Range Interactions: Theory and Experiments, held in Assisi, Italy during the period July 4--8, 2007. He gave a talk at the workshop entitled *Ginzburg-Landau Polynomials and the Asymptotic Behavior of the Magnetization in the Neighborhood of a Tricritical Point.*

Professor Paul Gunnells participated in the workshop Arithmetic Harmonic Analysis on Character and Quiver Varieties, which took place during the period June 4--8, 2007 at the American Institute of Mathematics in Palo Alto, California.

Professor Panos Kevrekidis gave a number of lectures during the past few months. In April 2007 he gave an invited talk at the 5th IMACS Meeting in Athens, GA. At the beginning of May, he visited the University of Kansas and gave a mathematics colloquium there. Panos then participated and presented an invited lecture in the first UMass-Heidelberg Workshop on Modeling and Computation in Physics, Mathematics and Biology, which took place at UMass Amherst during the period May 21ñ23. He then traveled to Snowbird, UT, where he gave another invited lecture at the SIAM Dynamical Systems Conference at the end of May. Finally, in June, he presented one of the six invited lectures at the Workshop on Analysis and its Applications, organized by the Mathematics Department of the University of Athens, Greece; Professor Markos Katsoulakis was also an invited speaker at the workshop. All of these talks focused on Panosí recent joint work with experimental and theoretical colleagues on the dynamics of Bose-Einstein condensates, optical solitary waves in photorefractive crystals, and acoustic waves in strongly nonlinear phononic crystals.

In June 2007 Professor Markos Katsoulakis co-organized the workshop Mathematical and Computational Methods for Accelerated Molecular, Stochastic and Hybrid Simulation, which was held at the Foundation for Research and Technology-Hellas (FORTH) in Crete Greece. The website and poster of the conference are available at the URL http://www.tem.uoc.gr/~workshop07/. Markos was also awarded a grant totaling $336,172 from the Division of Mathematical Sciences at the National Science Foundation for a project entitled *Multiscale Methods for Many-Particle Stochastic Systems: Coarse-Graining and Microscopic Reconstruction.* Among other activities the grant will support graduate students working on their PhDs during the period 2007--2010.

Visiting Assistant Professor Ralf Schiffler was awarded an NSF grant totaling $87,048 for the period 2007ñ2010 (DMS-0700358). He spent the period June 27--July 14, 2007 at the University of Sherbrooke, where he continued his joint research with I. Assem and T. Bruestle and gave two talks at the local algebra seminar. The titles of his talks were *Formules de Developpement dans les Algebres Amassees* and *Algebres Amassees et Surfaces Triangulees.* Ralf also attended the International Conference on Representations of Algebras (ICRA XII), which took place at the Nicolaus Copernicus University in Torun, Poland during the period August 15--24, 2007. At the conference he gave a talk entitled *Geometric Realizations of Cluster Categories.*

During July 2007 Professor John Staudenmayer became an Associate Editor of the Journal of the American Statistical Association, Theory and Methods Section.

Professor Jenia Tevelev received a grant from the National Science Foundation for his project entitled *Geometry of Compact Moduli Spaces* (DMS-0701191). He gave a talk entitled *Modular and Tropical Compactifications* during his stay at IHES in June and July 2007 and a second talk entitled *Mori-theoretic and Tropical Aspects of Terada, Naruki, and Sekiguchi Cross-ratio Varieties* during the conference Analysis and Geometry on Complex Varieties, which took place in Krasnoyarsk, Russia during the period August 15--20, 2007. Jeniaís paper entitled *Compactifications of Subvarieties of Tori* was published in the American Journal of Mathematics, 129, no. 4 (2007).

On June 25, 2007 Visiting Assistant Professor Yorghos Tripodis gave a talk at the International Symposium on Forecasting held in New York City. The title of the talk was *Forecasting in Linear Autoregressive Models with Heteroscedastic Measurement Error.* On July 30 he gave a talk entitled *Forecasting Contemporaneous Aggregated Time Series* at the Joint Statistical Meeting held in Salt Lake City.

Professor Emeritus Floyd Williams has been invited by the Mathematical Sciences Research Institute in Berkeley to organize a two-week graduate workshop in number theory and physics during the period June 16--27, 2008. Entitled *A Window into Zeta and Modular Physics,* the workshop will host up to forty students, including Floydís two Ph.D. students, Shabnam Beheshti and Jennie DíAmbroise. The lectures by Floyd and four other professors will cover the following topics: spectral and non-spectral zeta functions, heat kernel asymptotics, Bose-Einstein condensation, black holes and gravity in extra dimensions, and modular invariance in conformal field theory.