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Today, Monday, October 26, 2026

Posted October 23, 2026

Probability Seminar Questions or comments?

2:00 pm – 3:00 pm Click here to attend on Zoom

Milton Jara, IMPA, Brazil
Scaling limit of a population model with age

Consider the following simple dynamics. We start with a semi-infinite binary vector ((\ldots,X_{-1},X_0)). At each step, we draw a geometric random variable (Z), look (Z) steps into the past, and copy the bit we see at that position. This dynamics can be interpreted as a modification of the Moran model, in which the probability that an individual passes a trait (represented by a binary bit) to a given descendant is a function of its age and decays exponentially in time. When the parameter of the geometric random variable converges to 1, we show that the expected future value of the trait converges to a solution of the Wright–Fisher equation. For suitable generalizations of this model, we show that their scaling limits are given by solutions of the Fleming–Viot equation. Joint work with Eldon Barros and Eric Santana (IMPA).

Event contact: Yangrui Xiang

Posted October 25, 2026

Informal Combinatorics Seminar

2:30 pm – 3:30 pm Lockett 233

Weihao Xia, Louisiana State University
Introduction to Directed Graphs and Tournaments

We will give a brief introduction to directed graph theory, starting with basic definitions, degrees, paths, cycles, and connectivity. We will then discuss several important properties and classes of directed graphs, with a particular focus on tournaments and their Hamiltonian paths and cycles. We will explore classical results on pancyclicity in regular tournaments and extend our discussion to multipartite tournaments.

Event contact: jgarc86@lsu.edu

Tomorrow, Tuesday, October 27, 2026

Posted September 28, 2026
Last modified October 22, 2026

Algebra and Number Theory Seminar Questions or comments?

3:00 pm – 4:00 pm Lockett 233 or click here to attend on Zoom

Yifeng Huang, Emory University
Rogers--Ramanujan identities from singular curves

The first Rogers—Ramanujan identity $$\sum_{n\ge 0} \frac{q^{n^2}}{(1-q)(1-q^2)\cdots (1-q^n)}=\prod_{i\ge 1, i\equiv 1,4\pmod 5} (1-q^i)^{-1}$$ is an ``infinite sum=infinite product'' identity. Combinatorially, it means that partitions of $n$ with gaps between adjacent parts at least two are as many as partitions of $n$ whose parts are congruent to 1 or 4 modulo 5. Much less known is that the identity also counts zero-dimensional sheaves on the cuspidal curve $X^2=Y^3$, obtained in an earlier work with Jiang. In recent joint works with Jiang and Oblomkov and with Lau and Ono, we show that this phenomenon extends to any coprime $a,b$, resulting in infinitely many new Rogers—Ramanujan identities. It uses a wide range of ingredients, from Quot scheme of points, quiver representations, and poset flag varieties used in the geometric computation, to cylindric partitions, symmetric functions, and compositional rational shuffle theorem used in the proof of the new identities

Wednesday, October 28, 2026

Posted August 26, 2026
Last modified October 23, 2026

Informal Analysis Seminar Questions or comments?

12:30 pm – 1:20 pm Lockett 233

Majid Abubakar, Louisiana State University
Asymptotic and Non-asymptotic Analysis of Ergodic Jump Diffusion systems

Estimating integrals with respect to the stationary distribution of a Markov process X typically relies on time-averaged integrals. In many practical scenarios, such as when X is defined by a SDE with jumps, these integrals lack a closed-form solution, necessitating the use of a discretized process. This discrepancy is particularly pronounced in jump-diffusion settings. We establish convergence results and Central Limit Theorems for these time-inhomogeneous integrals, and present concentration inequalities that demonstrate non-asymptotic, exponential decay of error probabilities.

Event contact: Laura Kurtz

Posted September 15, 2026
Last modified October 13, 2026

Geometry and Topology Seminar Seminar website

1:30 pm – 2:30 pm Lockett 233

Colby Kelln, University of Minnesota
Filling flatly fibered cusps of hyperbolic $n$-manifolds

Dehn filling is a classical tool for producing negatively curved manifolds from cusped hyperbolic 3-manifolds, and results of Mosher-Sageev and Fujiwara-Manning extend this idea to higher dimensions when cusp cross sections are tori. In this talk, I will discuss a generalization to hyperbolic manifolds whose cusps can have more complicated cross sections---ones that admit a Riemannian submersion onto a flat base with totally geodesic fiber. Filling along the fibers of such a cusp can still produce a nonpositively (and in some cases negatively) curved space, provided that the fibers have large enough systole. Group theoretically, this filling takes a relatively hyperbolic fundamental group and creates a related hyperbolic one. I'll introduce the Ratcliffe-Tschantz hyperbolic 5-manifold, whose cusps are bundles with Hantzsche-Wendt fiber over the circle, and show how the filling result, coupled with some group theory, gives information about the geometry of its cusps.

Event contact: Jagerynn Ting Verano

Posted August 27, 2026
Last modified October 25, 2026

Informal Geometry and Topology Seminar Questions or comments?

3:30 pm Lockett Hall 233

Krishnendu Kar, Louisiana State University
Skein reduction and stabilization for the odd Khovanov spectra of T(2,m) ⊔ T(2,n)

Lipshitz and Sarkar refined Khovanov homology to a stable homotopy type: for each quantum grading, a finite spectrum whose cohomology is Khovanov homology. Sarkar, Scaduto and Stoffregen constructed the corresponding spectra for odd Khovanov homology. For a split link, the even spectrum is a smash product of the spectra of its pieces (Lawson--Lipshitz--Sarkar). The odd spectrum is not. By computations of Sch\"utz and a theorem of Rajapakse, the odd spectrum of $T(2,3)\sqcup T(2,3)$ in quantum grading $14$ contains a suspension of $\mathbb{CP}^2$, a summand not known to occur in any even Khovanov spectrum. How often does $\mathbb{CP}^2$ appear? For $T(2,m)\sqcup T(2,n)$, the odd spectrum in each quantum grading $q$ is a wedge of spheres and $\nu$ copies of a suspension of $\mathbb{CP}^2$, and homology cannot see $\nu$. Using the skein cofiber sequence at the level of spectra, I will show that $\nu$ vanishes in five quantum gradings, reduces to finitely many small links for fixed $q-m-n$, and stabilizes as $m$ and $n$ grow. In particular, the $\mathbb{CP}^2$ summand persists in grading $m+n+8$ for all $m,n\ge 3$.

Thursday, October 29, 2026

Posted October 21, 2026

Colloquium Questions or comments?

3:30 pm Lockett 232

Gunter Stolz, University of Alabama at Birmingham
Speed Limits for Quantum Walks in Electric Fields

Quantum walks can be motivated in at least two different ways. For one, they are the one-particle sector restrictions of quantum cellular automata (QCAs), a model used in quantum computing. Also, quantum walks are a quantum mechanical analog of classical random walks. However, while the latter have diffusive dynamics, quantum walks typically spread ballistically, i.e. they have positive velocity. We will discuss two ways to mathematically describe their propagation velocity. In particular, we will show that an exterior periodic electric field can slow down the velocity exponentially in the period of the field. This means that the field localizes the walk for long times, which thus behaves as an insulator. This is joint work with Houssam Abdul-Rahman (Arabic Emirates), Christopher Cedzich (Hagen, Germany) and Albert Werner (Copenhagen).

Friday, October 30, 2026

Posted September 21, 2026

Control and Optimization Seminar Questions or comments?

10:30 am – 11:20 am Zoom: https://lsu.zoom.us/j/98176468969

Tim Hoheisel, McGill University, Canada
A Computational Framework for Linear Inverse Problems via the Maximum Entropy on the Mean Method

We present a framework for solving linear inverse problems that is computationally tractable and has mathematical certificates. To this end, we interpret the ground truth of a linear inverse problem as a random vector with unknown distribution. We solve for a distribution which is close to a prior P (guessed or data-driven) measured in the KL-divergence while also having an expectation that yields high fidelity with the given data that defines the problem. After reformulation this yields a strictly convex, finite dimensional optimization problem whose regularizer, the MEM functional, is paired in duality with the log-moment generating function of the prior P. We exploit this computationally via Fenchel-Rockafellar duality. When no obvious guess for P is available, we use data to generate an empirical prior. Using techniques from variational analysis and stochastic optimization, we show that, and at what rate, the solution of the empirical problems converges (as the sample size grows) to the solution of the problem with known prior. Moreover, we show how stochastic subgradient methods can be brought to bear on the MEM dual. This is joint work with Rustum Choksi (McGill), Matthew King-Roskamp (McGill), and Gabriel Rioux (Imperial College).

Wednesday, November 4, 2026

Posted August 26, 2026

Informal Analysis Seminar Questions or comments?

12:30 pm – 1:20 pm Lockett 233

Jackson Knox, Louisiana State University
TBD (Dynamical Systems)

Event contact: Laura Kurtz

Posted September 25, 2026
Last modified October 17, 2026

Geometry and Topology Seminar Seminar website

1:30 pm – 2:30 pm Lockett 233

Steven Clontz, University of South Alabama
Database-Driven Mathematical Inquiry in Topology

Recent advances in computing have changed not only the nature of mathematical computation, but mathematical proof and inquiry itself. While artificial intelligence and formalized mathematics have been the major topics of this conversation, this talk will explore another class of tools for advancing mathematics research: databases of mathematical objects that enable semantic search, particularly the π-Base community database of topological counterexamples

Posted August 27, 2026

Informal Geometry and Topology Seminar Questions or comments?

3:30 pm Lockett Hall 233

Michael Young, Louisiana State University
TBD

TBD

Thursday, November 5, 2026

Posted October 16, 2026

Student Colloquium

10:30 pm TBD

Steven Clontz, University of South Alabama
Accessible and Interactive Mathematical Documents for Instruction

Beginning April 26, 2027, all public universities will be required to ensure digital documents posted online must be accessible to screenreader users. Compliance with the Americans with Disabilities Act can be quite tricky in mathematics, given our reliance on intricate formulas and graphics, and even interactive elements such as code or three-dimensional renders, for research and education. In this talk we will explore three particular tools for meeting this upcoming accessibility requirement: PreTeXt, Prefigure, and Doenet.

Friday, November 6, 2026

Posted September 30, 2026

Control and Optimization Seminar Questions or comments?

10:30 am – 11:20 am Zoom: https://lsu.zoom.us/j/98176468969

Daniel Wachsmuth, University of Wuerzburg, Germany
Solution Algorithms for Nonsmooth Optimal Control Problems Based on the Pontryagin Maximum Principle

The talk is motivated by optimal control problems for partial differential equations. The main interest is in problems that involve integral functions of the type \[\int_\Omega g(u(x)) \ dx,\] where $g : \mathbb R \to \mathbb R$ is nonsmooth and nonconvex, and $u$ is the control variable. Examples involve $L^{\scriptscriptstyle r}$-pseudonorms with $r\in [0,1)$ or problems with the constraint $u(x) \in \mathbb Z$ for $x\in \Omega$. Due to the nonconvexity of $g$, the existence of solutions in $L^{\scriptscriptstyle p}$-spaces cannot be proven. Local solutions (if they exist) can be proven to satisfy the Pontryagin maximum principle. A distinctive feature of this result is that no differentiability with respect to the control variable $u$ is required. The maximum principle serves as a starting point to develop an implementable solution algorithm. We prove that the residual in the maximum principle vanishes along the iterates produced by the algorithm. Under additional assumptions, the iterates are a minimizing sequence.

Tuesday, November 10, 2026

Posted August 22, 2026

Algebra and Number Theory Seminar Questions or comments?

3:00 pm – 4:00 pm Lockett 233 or click here to attend on Zoom

Isabella Negrini, University of Toronto
TBA

Event contact: Gene Kopp

Wednesday, November 11, 2026

Posted August 26, 2026

Informal Analysis Seminar Questions or comments?

12:30 pm – 1:20 pm Lockett 233

Ruben Acevedo Acevedo, Louisiana State University
TBD (Spectral Theory)

Posted September 15, 2026

Geometry and Topology Seminar Seminar website

1:30 pm – 2:30 pm Lockett 233

Federico Galetto, Cleveland State University
TBA

Event contact: Christin Bibby

Posted August 27, 2026
Last modified October 13, 2026

Informal Geometry and Topology Seminar Questions or comments?

3:30 pm Lockett Hall 233

Yongho Lee, Louisiana State University
TBD

TBD

Friday, November 13, 2026

Posted September 21, 2026

Control and Optimization Seminar Questions or comments?

10:30 am – 11:20 am Zoom: https://lsu.zoom.us/j/98176468969

Radu Bot, University of Vienna
TBA

Tuesday, November 17, 2026

Posted September 20, 2026

Algebra and Number Theory Seminar Questions or comments?

3:00 pm – 4:00 pm Lockett 233 or click here to attend on Zoom

Ngoc Trinh Le, Tulane University
TBA

Event contact: Gene Kopp

Posted September 30, 2026
Last modified October 17, 2026

Computational Mathematics Seminar

3:30 pm – 4:20 pm LDMC, Room 1034

Gonzalo Benavides, University of Maryland
A priori error analysis of conforming discretizations of the ferrofluids Shliomis model without magnetic regularization

We develop and analyze a family of conforming, energy-stable spatial semidiscretizations of the Shliomis ferrofluid model without magnetic diffusion in two and three space dimensions. The limited spatial control supplied by the energy law complicates the treatment of magnetic nonlinearities in the error analysis. Our formulation retains the rotational coupling and incorporates the magnetic normal-flux condition naturally, overcoming the dimensional restriction and boundary-enforcement difficulties of the two-potential approach of Benavides, Nochetto and Shakipov (2026). The error analysis combines consistent stabilization of the Maxwell constraint with a cancellation arising from exact incompressibility and the pointwise symmetry of the Hessian of the magnetic potential. We prove global solvability and establish a priori error estimates for sufficiently regular exact solutions under explicit approximation and projection-stability assumptions. These assumptions are verified for concrete finite element spaces in two dimensions, while the three-dimensional error estimates remain conditional on a highly likely, but still unverified, uniform $\mathrm{W}^{1,\infty}$-stability of an appropriate incompressibility-preserving projector. Of independent interest and following Girault and Scott (2002), we construct an averaged $\mathrm{H}^2$-conforming projector that is well-defined on $\mathrm{L}^1(\Omega)$. For the Hsieh--Clough--Tocher and Walkington macroelement families considered, we establish optimal approximation estimates in $\mathrm{W}^{j,p}(\Omega)$, $j=0,1,2$, and stability in $\mathrm{W}^{2,p}(\Omega)$ for every $p \in [1,\infty]$ on general shape-regular triangulations.

Event contact: Shawn Walker

Wednesday, November 18, 2026

Posted August 26, 2026

Informal Analysis Seminar Questions or comments?

12:30 pm – 1:20 pm Lockett 233

Moisés Gómez-Solís, Louisiana State University
TBD (Spectral Theory)

Event contact: Laura Kurtz

Posted September 15, 2026

Geometry and Topology Seminar Seminar website

1:30 pm – 2:30 pm Lockett 233

Kushlam Srivastava, University of Wisconsin-Milwaukee
TBA

Event contact: Pallavi Dani