Calendar
Posted January 22, 2026
Informal Analysis Seminar Questions or comments?
12:30 pm – 1:30 pm Lockett 233
Hari Narayanan, Louisiana State University
Crash Course on Schrödinger Operators (Part 1)
An expository talk in spectral theory.
Posted January 28, 2026
Geometry and Topology Seminar Seminar website
1:30 pm 233 Lockett Hall
Konrad Wrobel, University of Texas at Austin
Measure equivalence classification of Baumslag-Solitar groups
We complete the classification of Baumslag-Solitar groups up to measure equivalence by showing all Baumslag-Solitar groups with nonunimodular Bass-Serre tree are measure equivalent (i.e., BS(r,s) with r between 1 and s). The proof makes critical use of combinatorial descriptive set theory tools in the measure class preserving setting and passes through the world of measure equivalence of nonunimodular locally compact groups. In particular, as an intermediate step we obtain measure equivalence couplings between all groups of the form Aut(T_{r,s}) for r between 1 and s where T_{r,s} is the directed tree with r incoming edges and s outgoing edges at each vertex. This is joint work with Damien Gaboriau, Antoine Poulin, Anush Tserunyan, and Robin Tucker-Drob.
Posted February 3, 2026
Discussion and Training in Combinatorics
2:30 pm Lockett 233
Joy Harris
Ramsey Number of Daisies
Given the set of vertices $[n]=\{1,\ldots,n\}$, an \emph{$r$-daisy}, given by disjoint sets $K,M \subset [n]$, is the $(r+|K|)$-uniform hypergraph defined as \[ \{K \cup P : P \subset M \text{ and } |P|=r\}. \] In this talk, we will discuss the \emph{Ramsey number of daisies}. This is the minimum number of vertices $n$ such that no coloring of the subsets of $[n]$ by $\ell$ colors yields a monochromatic daisy. We will give a probabilistic proof showing a lower bound for this number.
Event contact: Gyaneshwar Agrahari and Emmanuel Asante
Posted January 15, 2026
Last modified February 4, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Matthew Lemoine, Louisiana State University
Sliding Window Embedding
When we are looking at a dataset that has a time-dependency and is periodic (or quasi-periodic), we are interested in noticing differences in the period. Using sliding window embeddings (also known as time-delay reconstructions), we can look at the periods of a given dataset and analyze the persistent homology to detect changes in our periods. In this talk, we will be discussing the foundational paper in this area of Topological Data Analysis by Jose Perea and John Harer (arxiv:1307.6188).
Posted February 1, 2026
Last modified February 2, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:30 am Lockett 233 or Zoom (click here to join)
R. Tyrrell Rockafellar, University of Washington
Variational Analysis and Convexity in Optimal Control
Optimal control theory was considered by its originators to be a new subject which superseded much of the classical calculus of variations as a special case. In reality, it was more a reformulation of existing theory with different goals and perspectives. Now both can be united in a broader setting of variational analysis in which Lagrangian and Hamiltonian functions need not be differentiable or even continuous, but extended-real-valued, and convexity has a central role. The Control and Optimization Seminar for this talk will be held in person, with a Zoom option available for remote attendees.
Event contact: Gowri Priya Sunkara
Posted January 30, 2026
Combinatorics Seminar Questions or comments?
2:30 pm – 3:30 pm Lockett 233 (Simulcast via Zoom)
Tung Nguyen, University of Oxford, UK
Polynomial $\chi$-boundedness for excluding $P_5$
We discuss some ideas behind the recent resolution of a 1985 open problem of Gyárfás, that there is a positive integer k for which every graph with no induced five-vertex path has chromatic number at most the kth power of their clique number.
Posted December 29, 2025
Last modified February 3, 2026
Colloquium Questions or comments?
3:30 pm Lockett 232 or click here to attend on Zoom
R. Tyrrell Rockafellar, University of Washington
Dual Problems of Optimization
A surprising discovery in the early days of optimization theory was the prevalence of a new kind of duality. Typical problems then of interest, in which a linear function was to be minimized subject to constraints consisting of equations or inequalities imposed on other linear functions, couldn't be solved without simultaneously solving a partnered problem of maximization in the same category. The solutions to the two problems could be viewed moreover as the best strategies for two opponents is a sort of zero-sum game. This theme is now understood much more broadly as a feature of optimization theory that has been important not only in the design of solution algorithms, but also in extending mathematical analysis beyond the traditions of calculus.
Posted December 17, 2025
Last modified January 30, 2026
Applied Analysis Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett 223
Tuoc Phan, University of Tennessee–Knoxville
On Lin type Hessian estimates for solutions to a class of singular-degenerate parabolic equations
We disscuss a class of parabolic equations in non-divergence form with measurable coefficients that exhibit singular and/or degenerate behavior governed by weights in a Muckenhoupt class. We present new results on weighted F.-H. Lin type estimates of the Hessian matrices of solutions. As examples, we demonstrate that the results are applicable to equations whose leading coefficients are of logistic-type singularities, as well as those are of polynomial blow-up or vanishing with sufficiently small exponents. A central component of the approach is the development of local quantitative lower estimates for solutions, which are interpreted as the mean sojourn time of sample paths, a stochastic-geometric perspective that generalizes the seminal work of L. C. Evans. By utilizing intrinsic weighted cylinders and perturbation arguments alongside with parabolic ABP estimates, we effectively manage the operator's degeneracies and singularities. We also briefly address regularization and truncation strategies that ensure our estimates are robust. We conclude with a discussion of future applications and related developments in the field.
Posted January 15, 2026
Last modified February 3, 2026
Joshua Sabloff, Haverford College
Informal Discussion with Joshua Sabloff
Join us for an informal discussion with Joshua Sabloff. We will be discussion what it is like working in a primarily undergraduate institution.
Posted February 3, 2026
Last modified February 4, 2026
Joshua Sabloff, Haverford College
How to Tie Your Unicycle in Knots: An Introduction to Legendrian Knot Theory
You can describe the configuration of a unicycle on a sidewalk using three coordinates: two position coordinates x and y for where the wheel comes into contact with the ground and one angle coordinate t that describes the angle that the direction the wheel makes with the x axis. How are the instantaneous motions of the unicycle constrained (hint: do you want your tire to scrape sideways)? How can we describe that constraint using generalizations of tools from vector calculus? The system of constraints at every point in (x,y,t)-space is an example of a "contact structure," and a path that obeys the constraints is a "Legendrian curve." If the curve returns to its starting point, then it is called a "Legendrian knot." A central question in the theory of Legendrian knots is: how can you tell two Legendrian knots apart? How many are there? In other words, how many ways are there to parallel park your unicycle? There will NOT be a practical demonstration.
Posted January 22, 2026
Informal Analysis Seminar Questions or comments?
12:30 pm – 1:30 pm Lockett 233
Matthew McCoy, Louisiana State University
Crash Course on Schrödinger Operators (Part 2)
An expository talk in spectral theory.
Posted January 28, 2026
Last modified February 3, 2026
Geometry and Topology Seminar Seminar website
1:30 pm 233 Lockett Hall
Joshua Sabloff, Haverford College
On the Non-Orientable Genera of a Knot: Connections and Comparisons
We define a new quantity, the Euler-normalized non-orientable genus, to connect a variety of ideas in the theory of non-orientable surfaces bounded by knots. We use this quantity to explore the geography of non-orientable surfaces bounded by a fixed knot in 3 and 4 dimensions. In particular, we will use the Euler-normalized non-orientable genus to reframe non-orientable slice-torus bounds on the (ordinary) non-orientable 4-genus and to bound below the Turaev genus as a measure of distance to an alternating knot. This is joint work with Julia Knihs, Jeanette Patel, and Thea Rugg.
Posted February 4, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm Lockett Hall 233
Justin Lanier, Louisiana State University
TBD
TBD
Posted November 26, 2025
Last modified January 29, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Anthony Bloch, University of Michigan
AMS, IEEE, and SIAM Fellow
Control, Stability and Learning on Dynamic Networks
In this talk we consider various aspects of dynamics, control and learning on graphs. We discuss diffusively coupled network dynamical systems and the role of coupling in stabilizing and destabilizing such systems. We also discuss dynamic networks of this type and in particular Lyapunov-based methods for analyzing the stability of networks undergoing switching. In addition we analyze the problem of learning the dynamics of switched systems from data, including linear and polynomial systems and systems on graphs. In addition we consider the control and dynamics of systems on hypergraphs which have applications to biological networks.
Posted January 28, 2026
Geometry and Topology Seminar Seminar website
1:30 pm 233 Lockett Hall
Nilangshu Bhattacharyya, Louisiana State University
TBA
Posted December 7, 2025
Last modified December 28, 2025
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Richard Vinter, Imperial College London
IEEE Fellow
Control of Lumped-Distributed Control Systems
Lumped-distributed control systems are collections of interacting sub-systems, some of which have finite dimensional vector state spaces (comprising ‘lumped’ components) and some of which have infinite dimensional vector state spaces (comprising ‘distributed’ components). Lumped-distributed control systems are encountered, for example, in models of thermal or distributed mechanical devices under boundary control, when we take the control actuator dynamics or certain kinds of dynamic loading effects into account. This talk will focus on an important class of (possibly non-linear) lumped-distributed control systems, in which the control action directly affects only the lumped subsystems and the output is a function of the lumped state variables alone. We will give examples of such systems, including a temperature-controlled test bed for measuring semiconductor material properties under changing temperature conditions and robot arms with flexible links. A key observation is an exact representation of the mapping from control inputs to outputs, in terms of a finite dimensional control system with memory. (We call it the reduced system representation.) The reduced system representation can be seen as a time-domain analogue of frequency response descriptions involving the transfer function from input to output. In contrast to frequency response descriptions, the reduced system representation allows non-linear dynamics, hard constraints on controls and outputs, and non-zero initial data. We report recent case studies illustrating the computational advantages of the reduced system representation. We show that, for related output tracking problems, computation methods based on the new representation offer significantly improved tracking and reduction in computation time, as compared with traditional methods, based on the approximation of infinite dimensional state spaces by high dimensional linear subspaces.
Posted February 3, 2026
Mathematical Physics and Representation Theory Seminar
1:30 pm – 2:20 pm Lockett 233
Karl-Hermann Neeb, Universität Erlangen-Nürnberg
Coadjoint orbits carrying Gibbs ensembles
Coadjoint orbits are orbits for the action of a Lie group on the dual of its Lie algebra. They carry a natural symplectic structure and are models for homogeneous systems in classical mechanics. Gibbs measures on these orbits provide a natural setting for models of thermodynamic systems. We say that a coadjoint orbit carries a Gibbs ensemble if the set of all $x$, for which the function $\alpha \mapsto e^{-\alpha(x)}$ on the orbit is integrable with respect to the Liouville measure, has non-empty interior $\Omega_\lambda$. We describe a classification of all coadjoint orbits with this property. In the context of Souriau's Lie group thermodynamics, the subset $\Omega_\lambda$ is the geometric temperature, a parameter space for a family of Gibbs measures on the coadjoint orbit. The corresponding Fenchel--Legendre transform maps $\Omega_\lambda$ (modulo central shifts) diffeomorphically onto the interior of the convex hull of the coadjoint orbit $\cO_\lambda$. This provides an interesting perspective on the underlying information geometry.
Posted November 15, 2025
Last modified January 21, 2026
Algebra and Number Theory Seminar Questions or comments?
2:00 pm – 3:00 pm Lockett 233 or click here to attend on Zoom
Marco Sangiovanni Vincentelli, Columbia University
An Euler system for the adjoint of a modular form
Euler systems have proven to be versatile tools for understanding Selmer groups and their connections to special values of $L$-functions. However, despite the key role they have played in making progress toward foundational conjectures in number theory, such as the Birch and Swinnerton-Dyer and Bloch–Kato Conjectures, only a handful of provably non-trivial Euler systems have been constructed to date. A significant obstacle to constructing Euler Systems lies in producing candidate Galois cohomology classes. This lecture series presents joint work with Chris Skinner that develops a method to overcome this obstacle. Using this method, we construct an Euler system for the adjoint of a modular form.
Event contact: Gene Kopp
Posted January 28, 2026
Geometry and Topology Seminar Seminar website
1:30 pm 233 Lockett Hall
Nir Gadish, University of Pennsylvania
TBA
Posted January 15, 2026
Last modified January 16, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Hailey Garcia, Louisiana State University
TBD
TBD
Posted January 8, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Lars Gruene, University of Bayreuth
SIAM Fellow
Can Neural Networks Solve High Dimensional Optimal Feedback Control Problems?
Deep reinforcement learning has established itself as a standard method for solving nonlinear optimal feedback control problems. In this method, the optimal value function (and, in some variants, the optimal feedback law also) is stored using a deep neural network. Hence, the applicability of this approach to high-dimensional problems relies crucially on the network's ability to store a high-dimensional function. It is known that for general high-dimensional functions, neural networks suffer from the same exponential growth of the number of coefficients as traditional grid based methods, the so-called curse of dimensionality. In this talk, we use methods from distributed optimal control to describe optimal control problems in which this problem does not occur.
Posted January 19, 2026
Geometry and Topology Seminar Seminar website
1:30 pm Virtual
Ettore Marmo, Università degli Studi di Milano-Bicocca
TBA
Posted January 15, 2026
Last modified January 16, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Benjamin Appiah, Louisiana State University
TBD
TBD
Posted January 12, 2026
Applied Analysis Seminar Questions or comments?
3:30 pm Lockett Hall 232
Daniel Massatt, New Jersey Institute of Technology
TBA
Event contact: Stephen Shipman
Posted November 15, 2025
Last modified January 21, 2026
Algebra and Number Theory Seminar Questions or comments?
2:00 pm – 3:00 pm Lockett 233 or click here to attend on Zoom
Kiran Kedlaya, University of California San Diego
TBA
Event contact: Gene Kopp
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Sayani Mukherjee, Louisiana State University
TBD
TBD
Posted December 1, 2025
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Khai Nguyen, North Carolina State University
TBA
Posted January 11, 2026
Applied Analysis Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett 223
Zhiyuan Geng, Purdue University
TBA
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Saumya Jain, Louisiana State University
TBD
TBD
Posted January 15, 2026
Colloquium Questions or comments?
3:30 pm Lockett 232
Kumar Murty, University of Toronto
TBA
Posted January 5, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Jonathan How, Massachusetts Institute of Technology
AIAA and IEEE Fellow
TBA
Posted January 2, 2026
Last modified January 8, 2026
Control and Optimization Seminar Questions or comments?
10:30 am – 11:20 am Joint Computational Mathematics and Control and Optimization Seminar to Be Held In Person at Location TBA and on Zoom (click here to join)
Jia-Jie Zhu, KTH Royal Institute of Technology in Stockholm
TBA
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Krishnendu Kar, Louisiana State University
TBD
TBD
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Nilangshu Bhattacharyya, Louisiana State University
TBD
TBD
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Anurakti Gupta, Louisiana State University
TBD
TBD
Posted December 27, 2025
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Aris Daniilidis, Technische Universität Wien
TBA
Posted January 15, 2026
Last modified January 22, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Fabian Espinoza de Osambela, Louisiana State University
TBD
TBD
Posted January 2, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Behçet Açıkmeşe, University of Washington
AIAA and IEEE Fellow
Optimization-Based Design and Control for Next-Generation Aerospace Systems
Next-generation aerospace systems (e.g., asteroid-mining robots, spacecraft swarms, hypersonic vehicles, and urban air mobility) demand autonomy that transcends current limits. These missions require spacecraft to operate safely, efficiently, and decisively in unpredictable environments, where every decision must balance performance, resource constraints, and risk. The core challenge lies in solving complex optimal control problems in real time, while (i) exploiting full system capabilities without violating safety limits, (ii) certifying algorithmic reliability for critical guidance, navigation, and control (GNC) systems, and (iii) co-designing hardware and software subsystems for optimal end-to-end performance. Our solution is optimization-based autonomy. By transforming GNC challenges into structured optimization problems, we achieve provably robust, computationally tractable solutions. This approach has already revolutionized aerospace, e.g., reusable rockets land autonomously via real-time trajectory planning, drones navigate dynamic obstacles, and spacecraft perform precision docking, all powered by algorithms that solve optimization problems with complex physics-based equations and inequalities in milliseconds. Emerging frontiers (such on-orbit satellite servicing, multi-vehicle asteroid exploration, large-scale orbital spacecraft swarms, and global hypersonic transport) push these methods further. Yet barriers remain, e.g., handling non-convex constraints, ensuring solver resilience, large-scale optimization for decision making and co-design, and bridging the gap between theory and flight-ready systems. This talk explores how real-time optimization is rewriting the rules of autonomy, and how researchers can turn these innovations into practice, propelling aerospace engineering into an era where aerospace systems think, adapt, and perform at the edge of the possible.
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Huong Vo, Louisiana State University
TBD
TBD
Posted January 24, 2026
Control and Optimization Seminar Questions or comments?
10:30 am – 11:20 am Note the Special Seminar Time. Zoom (click here to join)
Michael Friedlander, University of British Columbia
SIAM Fellow
Seeing Structure Through Duality
Duality is traditionally introduced as a source of bounds and shadow prices. In this talk I emphasize a second role: revealing structure that enables scalable computation. Starting from LP complementary slackness, I describe a generalization called polar alignment that identifies which "atoms" compose optimal solutions in structured inverse problems. The discussion passes through von Neumann's minimax theorem, Kantorovich's resolving multipliers, and Dantzig's simplex method to arrive at sublinear programs, where an adversary selects worst-case costs from a set. The resulting framework unifies sparse recovery, low-rank matrix completion, and signal demixing. Throughout, dual variables serve as certificates that decode compositional structure.
Posted January 5, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Necmiye Ozay, University of Michigan
IEEE Fellow, and ONR Young Investigator, NASA Early Career Faculty, and NSF CAREER Awardee
TBA