Calendar
Posted January 4, 2026
Last modified January 8, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Alberto Bressan, Penn State
Eberly Family Chair Professor
Dynamic Blocking Problems for a Model of Fire Confinement
A classical problem in the Calculus of Variations asks to find a curve with a given length, which encloses a region of maximum area. In this talk I shall discuss the seemingly opposite problem of finding curves enclosing a region with minimum area. Problems of this kind arise naturally in the control of forest fires, where firemen seek to construct a barrier, minimizing the total area of the region burned by the fire. In this model, a key parameter is the speed at which the barrier is constructed. If the construction rate is too slow, the fire cannot be contained. After describing how the fire propagation can be modeled in terms of a PDE, the talk will focus on three main questions: (1) Can the fire be contained within a bounded region? (2) If so, is there an optimal strategy for constructing the barrier, minimizing the total value of the land destroyed by the fire? and (3) How can we find optimal strategies? Problem (1) is still largely open. See https://sites.psu.edu/bressan/2-research/ for a cash prize that has been offered for its solution since 2011.
Posted January 9, 2026
Last modified January 21, 2026
Informal Analysis Seminar Questions or comments?
12:30 pm – 1:30 pm Lockett 233
Maganizo Kapita, Louisiana State University
Statistical Learning of Stochastic Reaction Networks from Event-Time Data
tbd
Posted January 15, 2026
Last modified January 20, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett Hall 233
Nilangshu Bhattacharyya, Louisiana State University
From Khovanov homology to its stable homotopy refinement
Khovanov homology assigns a knot or a link to a bigraded homology theory that categorifies the Jones polynomial. It has concrete applications, for instance Rasmussen’s $s$-invariant, extracted from Lee’s deformation, which gives a lower bound on the smooth slice genus. At the same time, while the theory is very combinatorial and closely tied to the representation theory of $U_q(\mathfrak{sl}_2)$, it can be hard to see the underlying geometric picture directly from the homology groups. The stable homotopy refinement, introduced by Lipshitz and Sarkar, upgrades Khovanov homology to a space level invariant: a spectrum whose cohomology recovers Khovanov homology while supporting additional structure that is invisible in homology. In this talk, I will start with the construction of Khovanov homology and then gradually move toward its stable homotopy refinement. My work uses this viewpoint to build and study stable homotopy types beyond classical links, including planar trivalent graphs with perfect matchings, and to connect these refinements with themes from contact geometry and Floer theoretic settings.
Posted December 1, 2025
Last modified January 9, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Jameson Graber, Baylor University
NSF CAREER Awardee
Remarks on Potential Mean Field Games
Mean field games were introduced about 20 years ago to model the limit of N-player differential games as N goes to infinity. There are many applications to economics, finance, social sciences and biology. In many interesting cases the Nash equilibrium turns out to be a critical point for a functional, called the potential, in which case the game itself is called potential. In this case I will present several mathematical results on potential mean field games, which are directly connected to the theory of optimal control of PDE. For related work, see https://doi.org/10.1007/s40687-024-00494-3.
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
Olivia Beckwith, Tulane University
Polyharmonic Maass forms and Hecke series for real quadratic fields
We study polyharmonic Maass forms and show that they are related to ray class extensions of real quadratic fields. In particular, we generalize work of Lagarias and Rhoades to give a basis for the space of polyharmonic Maass forms for $\Gamma(N)$. Modifying an argument of Hecke, we show that twisted traces of cycle integrals of certain depth 2 polyharmonic Maass forms are leading coefficients of Hecke $L$-series of real quadratic fields. This is ongoing joint work with Gene Kopp.
Event contact: Gene Kopp
Posted January 22, 2026
Informal Analysis Seminar Questions or comments?
12:30 pm – 1:30 pm Lockett 233
Han Nguyen, LSU
Introduction to Finite Element Methods
This talk serves as an exposition of ongoing work in Finite Element Methods.
Posted January 15, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm – 4:30 pm 233 Lockett HallTo Be Filled In
Posted November 22, 2025
Last modified January 6, 2026
Control and Optimization Seminar Questions or comments?
9:30 am – 10:20 am Zoom (click here to join)
Henk van Waarde, University of Groningen
IEEE L-CSS Outstanding Paper and SIAM SIAG/CST Prize Awardee
Data-Driven Stabilization using Prior Knowledge on Stabilizability and Controllability
Direct approaches to data-driven control design map raw data directly into control policies, thereby avoiding the intermediate step of system identification. Such direct methods are beneficial in situations where system modelling is computationally expensive or even impossible due to a lack of rich data. We begin the talk by reviewing existing methods for direct data-driven stabilization. Thereafter, we discuss the inclusion of prior knowledge that, in conjunction with the data, can be used to improve the sample efficiency of data-driven methods. In particular, we study prior knowledge of stabilizability and controllability of the underlying system. In the case of controllability, we prove that the conditions on the data required for stabilization are equivalent to those without the inclusion of prior knowledge. However, in the case of stabilizability as prior knowledge, we show that the conditions on the data are, in general, weaker. We close the talk by discussing experiment design methods. These methods construct suitable inputs for the unknown system, in such a way that the resulting data contain enough information for data-driven stabilization (taking into account the prior knowledge).
Posted January 26, 2026
Last modified January 27, 2026
Combinatorics Seminar Questions or comments?
2:30 pm – 3:30 pm Lockett 233 (Simulcast via Zoom)
Xiaonan Liu, Vanderbilt University
Counting $k$-cycles in $5$-connected planar triangulations
We show that every $n$-vertex $5$-connected planar triangulation has at most $9n-50$ many cycles of length $5$ for all $n\ge 20$ and this upper bound is tight. We also show that for every $k\geq 6$, there exists some constant $C(k)$ such that for sufficiently large $n$, every $n$-vertex $5$-connected planar graph has at most $C(k) \cdot n^{\lfloor k/3 \rfloor}$ many cycles of length $k$. This upper bound is asymptotically tight for all $k\geq 6$. This is joint work with Gyaneshwar Agrahari and Zhiyu Wang.
Posted January 16, 2026
Last modified February 2, 2026
Algebra and Number Theory Seminar Questions or comments?
2:00 pm – 3:00 pm Lockett 233 or click here to attend on Zoom
Koustav Mondal, Louisiana State University
Theta series and their applications
Theta series play a central role in many areas of mathematics, especially number theory. In this talk, we begin with a brief overview of two applications of theta series: point counting for congruent quadratic forms, and the evaluation of special values of $L$-functions via Ramanujan's theory of elliptic functions to alternative bases for modular forms. Along the way, we state our main results in each setting. In the second part of the talk, we return to these applications to outline the key ideas and techniques involved in the proofs, as time permits.
Event contact: Gene Kopp
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 February 8, 2026
Applied Analysis Seminar Questions or comments?
3:30 pm – 4:30 pm Lockett 232
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
Last modified February 5, 2026
Informal Geometry and Topology Seminar Questions or comments?
3:30 pm Lockett Hall 233
Justin Lanier, Louisiana State University
Every Surface is a Leaf
We'll start by discussing the fact that every closed 3-manifold admits foliations, where the leaves are surfaces. This fact raises the question: for a given closed 3-manifold, which surfaces can appear as leaves of some foliation of that 3-manifold? Kerékjártó and Richards gave a classification up to homeomorphism of noncompact surfaces, which includes surfaces with infinite genus or infinitely many punctures. In their 1985 paper "Every surface is a leaf", Cantwell–Conlon prove a universality theorem: for every closed 3-manifold M and every orientable noncompact surface L, M has a foliation where L appears as a leaf. We will discuss their paper and the surrounding context.
Posted February 6, 2026
5:30 pm Lockett HallASA x Cabe C.
We will be joined by the President of Lewis and Ellis (LSU Alumni!!!) Pizza Will be served
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 February 8, 2026
Combinatorics Seminar Questions or comments?
2:30 pm – 3:30 pm Lockett 233 (Simulcast via Zoom)
Yiwei Ge, Louisiana State University
Extremal connectivity in graphs
A $k$-connected graph is minimally (respectively, critically) $k$-connected if the deletion of any edge (respectively, vertex) results in a graph that is not $k$-connected. A graph is uniformly $k$-connected if there are exactly $k$ internally disjoint paths between every pair of vertices. These classes have played a prominent role in graph connectivity theory. We introduce super-minimally $k$-connected graphs, defined as $k$-connected graphs with no proper $k$-connected subgraph. In this talk, we will give a brief introduction to these connectivity classes, with particular emphasis on extremal problems for $3$-connected graphs.