# Faculty News Briefs

### March 2018

On 21 February, Visiting Assistant Professor Jeremiah Birrell spoke in the Mathematical Physics and Probability Seminar at the University of Arizona; his talk was titled "Small Mass Limit of Noisy Inertial Particle Dynamics: Homogenization, Instantaneous Equilibration, and Entropy Production."

The 2017 William Lowell Putnam exam results are in: out of 575 participating institutions in the US and Canada, UMass Amherst ranked 46th, an excellent result! (Last year we ranked 55th out of 568.) Our three team members were Alexander Fischer, James Hagborg and Artem Vysogorets. James did particularly well, placing in the top 7% of the 4638 students taking the Putnam last December; Patrick Lei also had a noteworthy individual performance. Many thanks to VAP Liubomir Chiriac for his fine job running the Putnam seminar last fall.

Assistant Professor Nestor Guillen is applying his professional expertise to the topic of Gerrymandering. On 4 February he spoke at the Austin Gerrymandering Workshop, with a presentation about optimal transport and calculus of variations perspectives on redistricting. Nestor was also a part of the “Gerrymandering Steals Elections: Learn How It’s Done and How to Stop It" panel in Northampton on 12 February; moderated by former mayor Clare Higgins, other panelists were U. S. Representative Jim McGovern, State Representative Paul Mark, and Adam Hilton of Mount Holyoke College.

Assistant Professor Alejandro Morales gave the colloquium at the Tulane University math department on 29 February (OK, 1 March). His topic was "Volume and lattice point formulas for flow polytopes."

### February 2018

The Department welcomes Professor Nathaniel Whitaker as our new Head! Nate succeeds Farshid Hajir, who was appointed late last summer as the UMass Senior Vice Provost for Academic Affairs.

Visiting Assistant Professor Eric Hall gave an invited talk about “Robust information divergences for model-form uncertainty arising from sparse data in random PDE” at the Center for Nonlinear Studies at Los Alamos National Lab on 9 January. In other news, VAP Hall has been awarded an Early Career Travel Grant from the American Mathematical Society to attend the 2018 ICM.

Professor Rob Kusner was invited to China for the first 3 weeks of January to work on the geometry of minimal surfaces in spheres with former UMass research fellow Wang Peng. On Friday the fifth, Kusner delivered a pair of lectures titled "Complex Polynomials Classifying Coplanar CMC Surfaces" at Tongji University in Shanghai; the following weekend he lectured on the same topic at a conference in Xiamen organized by Guan Bo, a former UMass Ph. D. student and postdoctoral visitor, now a professor at both Ohio State University and also Xiamen University. (Rob reports: the food was good, the math was great, and the fast intercity trains were simply amazing! :-)

At the beginning of January, a video on Alcuin numbers of graphs featuring Assistant Professor Annie Raymond was published on the Numberphile channel on YouTube.

### December 2017

On 7 December, the New York Times reported on a list of books banned by the Texas Department of Criminal Justice. The list includes novels by Dave Barry, Alice Walker, and Carl Hiassen; a 1908 Sears, Roebuck catalogue; and a popup version of A Charlie Brown Christmas. The 10,000 banned titles, compiled by staff in prison mailrooms, also includes Merriam-Webster’s Guide to Everyday Math, written by Senior Lecturer Brian Burrell. Choices were made on the basis of "graphic sexual content" – not a problem in this instance – or "material that could help inmates make a weapon, plot an escape, or stir disorder." Surprisingly, no other math books have been banned. Nor were American Psycho or Mein Kampf on the list. Whether it is a greater honor to be on the banned list or on the approved list is not clear. Burrell is happy simply to have been included on either one.

On 16 November, Professor Erin Conlon gave the Department of Mathematics and Statistics seminar at the University of Maine; her lecture was titled "Parallel Markov Chain Monte Carlo Methods for Bayesian Analysis of Big Data."

Professor Paul Hacking has been invited to deliver a lecture at the 2018 International Congress of Mathematicians (ICM) to be held on 1-9 August 2018 in Rio de Janeiro, Brazil. He will speak in the section on Algebraic and Complex Geometry, together with his collaborator Sean Keel from the University of Texas-Austin. The ICM has been held roughly every four years, starting in 1897; it is one of the premier forums for presenting and discussing significant new mathematical discoveries.

Professor Markos Katsoulakis was recently nominated to serve on the editorial board of the Society for Industrial and Applied Mathematics (SIAM) Journal of Uncertainty Quantification . While SIAM has an enviable reputation for producing high quality publications across the full range of applied mathematics, this journal holds a special place in the SIAM line-up. Established in 2013 as a joint venture with the American Statistical Association, the SIAM Journal of Uncertainty Quantification is well-positioned in an era when links between applied mathematics and statistics are of growing importance. Markos has also been an editor of the SIAM journal Math Analysis.

At Penn's Minimal Surfaces Seminar on 21 November, Professor Rob Kusner talked about the "Morse index and Willmore stability of minimal surfaces in spheres."

Professor Franz Pedit gave a talk titled "Conformal flows minimizing the elastic (Willmore) energy for curves and surfaces" at the Oberseminar of the Leibnitz University Hannover on 8 November.

News Briefs will resume in the spring semester. Have a wonderful winter solstice and a perfectly pleasant perihelion!

### November 2017

On 6 October, Visiting Assistant Professor Stathis Charalampidis talked about "Nonlinear waves in Granular Crystals” at the William E. Boeing Department of Aeronautics & Astronautics of the University of Washington in Seattle.

During the week of 9-14 October , the first ever Student Competition Using Differential Equations Modeling (SCUDEM) event was held. UMass Amherst undergraduates Jonah Chaban, Artem Vysogorets, and Jimmy Hwang worked together as a team, and they produced the top-scoring project among the seven competing teams. On the first morning, all teams received access to three different modeling scenario prompts, and chose which to work on. Meeting throughout the week outside of class time, they devised a model, analyzed its behavior, determined parameters from real-world data, and wrote up their findings. On Saturday, the teams assembled at Mount Saint Mary College in Newburg, NY, where the students were presented with a new twist to their chosen scenario. In the afternoon, all groups presented their work to peers and faculty. Faculty sponsor Matthew Dobson participated in the Saturday event; he and Professor Nathaniel Whitaker also led practice sessions with the students.

On October 19, Professor Rob Kusner lectured about the "Willmore-stability of Minimal Surfaces in Spheres" at the Princeton University Geometric Analysis Seminar.

As a sequel to the ASA’s statement on p-values, Professor Michael Lavine spoke at the ASA’s Symposium on Statistical Inference during 11-13 October. The symposium’s purpose was to foster discussion on specific approaches for improving statistical practice as it intersects with conducting, using and disseminating research in the 21st century. He remains on the editorial board of Ecology, the flagship journal of the Ecological Society of America.

VAP Jacob Matherne and Professor Tom Braden visited MSRI the week of 9-13 October for a workshop Geometric and Topological Combinatorics: Modern Techniques and Methods.

Professor Bill Meeks was invited to be a senior participant in the Institute for Advanced Study's special program Variational Methods in Geometry during the fall of 2018.

Professor Franz Pedit was a keynote speaker at the Discrete Geometry and Dynamics Conference held at the Akademiezentrum of the Technical University Munich in the Raitenhaslach Monastery during 4-6 October. He talked on "Conformal flows minimizing the bending energy for curves and surfaces" and also reports windy weather in Germany.

Marshall H. Stone VAP Luca Schaffler lectured at SUNY Stony Brook about "The KSBA compactification of the moduli space of $D_{1,6}$-polarized Enriques surfaces" on 4 October.

### October 2017

The Dean of the College of Natural Sciences, Tricia Serio, has named Associate Head and Professor George Avrunin the Acting Head for the Fall 2017 semester, following Prof. Farshid Hajir's appointment late this summer as Senior Vice Provost for Academic Affairs (see below). The Department appreciates the wealth of experience George brings to the position, as well as his willingness to step forward on such short notice. The search for a new Head is now underway.

On 24 May, Visiting Assistant Professor Eric Hall spoke about joint work with Professors Markos Katsoulakis and Luc Rey-Bellet at a special session on data-driven modeling and prediction of dynamical systems at SIAM Dynamical Systems 2017; his invited talk was titled "Uncertainty quantification for generalized Langevin dynamics.” Eric also gave an invited talk "Robust information divergences for model-form uncertainty arising from sparse data in random PDE” about joint work with Katsoulakis at the North British Probability Seminar at the University of Edinburgh on 22 August. VAP Hall received an AMS-Simons Travel Grant which will provide up to \$4,000 over the period 2017-2019 for research-related travel and also includes a small annual amount to enhance the research environment of the Department. The grant is administered by the American Mathematical Society with support provided by the Simons Foundation . He also received a Collaborate @ ICERM grant, providing a small team of researchers funding to spend five days at the Institute for Computational and Experimental Research in Mathematics (ICERM), an NSF-funded research institute in Providence, RI. The collaboration with Mattias Sandberg (KTH) and Håkon Hoel (EPFL) will take place in summer 2018 and will make use of high performance computing resources available through Brown University's Center for Computation and Visualization.

Professor Michael Lavine became chair of the Savage Award committee in September. The award, in honor of Leonard Savage, is bestowed by the International Society for Bayesian Analysis each year on two doctoral dissertations in Bayesian econometrics and statistics, one in Theory and Methods, and one in Applied Methodology. In October he joined the National Institute of Standards and Technology’s Organization of Scientific Area Committees (OSAC) for Forensic Science Subcommittee on Friction Ridge Analysis (FRA) - the term “friction ridge” refers to fingerprints. The OSAC works to strengthen the nation’s use of forensic science by facilitating the development of technically sound standards and by promoting the adoption of those standards by the forensic science community. The FRA subcommittee includes forensic scientists from the FBI, police and sheriff departments.

VAP Jacob Matherne visited the University of Oklahoma the week of 20-25 July to collaborate with Greg Muller. Jacob took part in a 3-person Sage Coding Sprint from 6 to 11 August at the University of Minnesota's Institute for Mathematics and its Applications, implementing code to handle quivers for Double Bruhat cells. Between 13-17 August, Matherne and Tom Braden visited their collaborator Nicholas Proudfoot at the University of Oregon to collaborate on a project involving Kazhdan-Lusztig polynomials of matroids. On 9 and 10 September, Jacob gave invited talks in two special sessions of the AMS Sectional Meeting in Denton, TX: "Kazhdan-Lusztig polynomials for matroids" (joint work
with Braden and Proudfoot) in the special session on Combinatorics and Representation Theory of Reflection Groups: Real and Complex; and "Derived geometric Satake equivalence, Springer correspondence, and small representations" in the special session on "Noncommutative and Homological Algebra."

Professor Ivan Mirkovic lectured at the conferences Representation Theory XV in Dubrovnik, Croatia (18-25 June), and Interactions between Representation Theory and Algebraic Geometry at University of Chicago (21-26 August). He also visited the Mathematical Institute of the University of Bonn, Germany, the week of June 24-31, and gave a talk in their Representation Theory Seminar.

During the week August 14-18, Professor Franz Pedit attended the conference Higgs fields, harmonic maps, integrable systems at the Leibnitz University in Hannover, Germany, honoring Franz on his 60th birthday. The opening speaker was Professor Rob Kusner, who noted the Platonic significance of Franz's age, and then lectured on "Willmore stability of minimal surfaces in the n-sphere" (joint work with UMass visiting research professor PengWang from Tongji University, Shanghai, China). Among the other speakers was Dr. Nicholas Schmitt (former GANG senior scientist, and also Rob's 1993 PhD student here at UMass, now at Leibniz U). Franz also delivered three lectures on "The geometry of the self duality equations" at the BMS/SFB Summer School 2017 Discrete Models in Geometry and Mathematical Physics at Technical University Berlin in September.

Professor Hongkun Zhang was invited to give a plenary talk on "Diffusion for Sinai billiards with flat points" at the 5-9 June conference Modern Trends in the Ergodic Theory of Dynamical Systems in Rome, Italy; and two seminar talks in WuHan, China, on 1-2 August: "Improved Young tower for hyperbolic systems with singularities" at Central China Normal University, and "Diffusion for Lorentz gas with flat points" at Huazhong University of Science and Technology. During the week of 8-12 August, Hongkun organized the Dynamical Systems Section at the Second USA-Uzbekistan Conference on Analysis and Mathematical Physics, at Urgench State University, Uzbekistan, where she also spoke on "Improved Young tower for hyperbolic systems with singularities." And the weekend of 22-23 September, she organized the conference on Mathematical Physics Perspective of Billiards and Dominoes at UMass Amherst with Luc Rey-Bellet and Jianyu Chen; the plenary speakers included 4 members of the National Academy of Sciences: Joel Lebowitz, Gregory Margulis, Yakov Sinai, and Lai-Sang Young (Margulis is also a Fields Medalist, and Sinai is an Abel Prize awardee).