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Week of January 1, 2026

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January 13, 2026
Special Guest Lecture [3] Positroids, knots, and q,t-Catalan numbers Pavel Galashin - 4:00pm -
KT 801
Positroids, knots, and q,t-Catalan numbers Pavel Galashin - Cornell University 4:30pm -
TBA
January 14, 2026
Special Guest Lecture [3] Introduction to Spin Glass Theory Yuxin Zhou - University of Chicago 10:00am -
KT 801
Special Guest Lecture [3] Where can free waves concentrate Ruixiang Zhang - University of California, Berkeley 11:15am -
KT 801
Colloquium [4] The Convexity Conjecture, the Kahn-Kalai Conjecture, and introduction to k-thresholds Jinyoung Park - NYU 4:00pm -
KT 205
January 15, 2026
Special Guest Lecture [3] Mathematical Exploration and Discovery at Scale Javier Gomez-Serrano - Brown University 10:00am -
KT 801
Quantum Topology and Field Theory [5] Finiteness of Kauffman bracket skein modules Giulio Belletti - UC Louvain 4:30pm -
KT 801
January 22, 2026
Quantum Topology and Field Theory [5] Categorifying the Schur index of Seiberg-Witten theory Ahsan Khan - Harvard University 4:00pm -
KT 801
January 23, 2026
Quantum Topology and Field Theory [5] Deformation theory of vertex algebras and 'free field realizations from the Higgs branch Dylan Butson - UCLA 2:00pm -
KT 801
Learning seminar on Groups, Geometry and Dynamics [6] Ergodicity of geodesic flows. Sebastian Hurtado - 4:00pm -
KT 801
January 26, 2026
Geometric Analysis and Application [7] Index and nullity of minimal surfaces Jiahua Zou - Rutgers University 3:45pm -
KT 906
January 27, 2026
Geometry, Symmetry and Physics [8] Tate-Shafarevich twists of Lagrangian fibrations David Bai - Yale Univeristy 4:30pm -
KT 801
January 29, 2026
Analysis [9] Lattice packing of spheres in high dimensions using a stochastically evolving ellipsoid Boaz Klartag - Weizmann Institute 4:00pm -
Quantum Topology and Field Theory [5] A whittled complex for the Khovanov homology of torus braids Christine Lee - Texas State University 4:30pm -
KT 801
January 30, 2026
Learning seminar on Matroids and Algebraic Cycles [10] Learning seminar on Matroids and Algebraic Cycles Junliang Shen - Yale University 2:15pm -
KT 801
Learning seminar on Groups, Geometry and Dynamics [6] (Infinite) approximate groups. Gal Yehuda - 4:00pm -

Abstracts

Week of January 1, 2026

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January 13, 2026
Special Guest Lecture [3] Positroids, knots, and q,t-Catalan numbers 4:00pm -
KT 801

Abstract: Open positroid varieties are certain subvarieties of the Grassmannian that arise in the study of total positivity and have surprising applications in many areas of mathematics and physics. After reviewing some history and background, I will discuss our recent joint work with Thomas Lam relating the cohomology of these varieties and their point counts over finite fields to knot invariants such as the HOMFLYPT polynomial and Khovanov–Rozansky homology. In particular, we show that the bigraded Poincaré polynomials of top-dimensional open positroid varieties are given by rational q,t-Catalan numbers. No background on the above objects will be assumed.

Positroids, knots, and q,t-Catalan numbers 4:30pm -
TBA

Abstract: Open positroid varieties are certain subvarieties of the Grassmannian that arise in the study of total positivity and have surprising applications in many areas of mathematics and physics. After reviewing some history and background, I will discuss our recent joint work with Thomas Lam relating the cohomology of these varieties and their point counts over finite fields to knot invariants such as the HOMFLYPT polynomial and Khovanov–Rozansky homology. In particular, we show that the bigraded Poincaré polynomials of top-dimensional open positroid varieties are given by rational q,t-Catalan numbers. No background on the above objects will be assumed.

January 14, 2026
Special Guest Lecture [3] Introduction to Spin Glass Theory 10:00am -
KT 801

Abstract: Spin glasses are disordered magnetic systems that display remarkably complex collective behavior. Understanding these systems has challenged both physicists and mathematicians for decades. In the late 1970s, Giorgio Parisi proposed a revolutionary solution to the Sherrington–Kirkpatrick model. At the heart of his theory is the Parisi measure, an object that reveals the hidden organization of disorder. In this talk, I will survey what is now rigorously known about the Parisi measure and highlight the ​major open problems in the field.

Special Guest Lecture [3] Where can free waves concentrate 11:15am -
KT 801

Abstract: Waves are ubiquitous in our daily life. Two best-known linear models are the free wave and free Schrödinger equations, whose simplest forms are very amenable to Fourier analysis. Still, a basic question—how large can a solution be, and where can it be large?—is surprisingly subtle and only partly understood, especially in higher dimensions. Over decades, it transpired that in order to answer this fundamental question, one often needs to understand whether and how much the solution can concentrate on important subsets of $\mathbb{R}^n$. I will discuss three kinds of such subsets (convex sets, semialgebraic sets and lattices) and their importance based on sample problems. Some of them have nice connections to nearby areas such as number theory, geometry and combinatorics.

Colloquium [4] The Convexity Conjecture, the Kahn-Kalai Conjecture, and introduction to k-thresholds 4:00pm -
KT 205

Abstract: The “Convexity Conjecture” by Talagrand asks (very roughly) whether one can “create convexity” in constant steps regardless of the dimension of the ambient space. Talagrand also suggested a discrete version of the Convexity Conjecture and called it “my lifetime favorite problem,” offering $1,000 prize for its solution. We introduce a reformulation of the discrete Convexity Conjecture using the new notion of “k-thresholds,” which is an extension of the traditional notion of thresholds, introduced by Talagrand. Some ongoing work on understanding k-thresholds, along with a (vague) connection between the Kahn-Kalai Conjecture and the discrete Convexity Conjecture, will also be discussed. Joint work with Ascoli, He, and Talagrand.

January 15, 2026
Special Guest Lecture [3] Mathematical Exploration and Discovery at Scale 10:00am -
KT 801

Machine learning is transforming mathematical discovery, enabling advances on longstanding open problems. In this talk, I will discuss AlphaEvolve, a general-purpose evolutionary coding agent that uses large language models to autonomously discover old and new mathematical constructions and potentially go beyond them. AlphaEvolve tackles a wide variety of problems across analysis, geometry, combinatorics, and number theory. In some instances, AlphaEvolve is also able to generalize results for a finite number of input values into a formula valid for all input values. Furthermore, we are able to combine this methodology with Deep Think and AlphaProof in a broader framework where the additional proof-assistants and reasoning systems provide automated proof generation and further mathematical insights. This illustrates how general-purpose AI systems can systematically successfully explore broad mathematical landscapes at an unprecedented speed, leading us to do mathematics at scale.

Quantum Topology and Field Theory [5] Finiteness of Kauffman bracket skein modules 4:30pm -
KT 801

Skein modules are algebraic objects that somehow “encode” links in a 3-dimensional manifold, in a way reminiscent of homology; they have many interesting connections to physics, representation theory, knot theory (via the Jones polynomial) and non-commutative algebra. In this talk I will give a broad introduction and overview of the topic and then discuss a new, elementary proof (due to myself and Renaud Detcherry) of finite dimensionality of the Kauffman bracket skein modules, originally done by Gunningham-Jordan-Safronov.

January 22, 2026
Quantum Topology and Field Theory [5] Categorifying the Schur index of Seiberg-Witten theory 4:00pm -
KT 801

The”Schur index” is typically defined as a protected operator count in 4d N=2 superconformal field theories. It turns out in fact that one can define it for a generic 4d N=2 theory, conformal or not, by using the holomorphic-topological twist. Its categorification, namely the space of holomorphic-topological local operators, is expected to be a Poisson vertex algebra. However, for a general non-conformal theory, not much is known about the shape of this PVA. For 4d N=2 gauge theories with matter, I will formulate this PVA as a (relative) Lie algebra cohomology problem and then for the case of pure SU(2) Seiberg-Witten theory propose an explicit answer for the cohomology.

January 23, 2026
Quantum Topology and Field Theory [5] Deformation theory of vertex algebras and 'free field realizations from the Higgs branch 2:00pm -
KT 801

I will explain some results on the localization and deformation theory of vertex algebras, algebraic objects encoding a class of topological associative algebras generalizing the enveloping algebra of an affine Kac-Moody Lie algebra. I will also explain how these results can be used to give geometric constructions of free field realizations, embeddings of these algebras into infinite dimensional Weyl algebras, motivated by the physics of 4d N=2 superconformal field theories. All new results that will be presented are in joint work with Sujay Nair.

Learning seminar on Groups, Geometry and Dynamics [6] Ergodicity of geodesic flows. 4:00pm -
KT 801

I will give an introductory talk about the  ergodicity of geodesic flows, Anosov diffeomorphisms, the Hopf argument, and the Howe-Moore Theorem. Everybody is welcome, we will go for pizza after the talk.

January 26, 2026
Geometric Analysis and Application [7] Index and nullity of minimal surfaces 3:45pm -
KT 906

We discuss the strategies and results on the determination of index and nullity of minimal surfaces. In particular, we prove that for any large enough $m$, the genus $\gamma=m+1$ equator-poles minimal surface doubling of the equatorial two-sphere in the round three-sphere, which has two catenoidal bridges at the poles and  $m$ bridges equidistributed along the equatorial circle and was discovered in earlier work of Kapouleas, has index $2g+5=2m+7$ and nullity $6$.  We also discuss the progress in the study of indices of minimal surfaces from similar constructions.

https://yale.zoom.us/j/92334178441?pwd=FmjkR0LeihzxyR7AaNzsvTIPa11tmK.1 [13]

January 27, 2026
Geometry, Symmetry and Physics [8] Tate-Shafarevich twists of Lagrangian fibrations 4:30pm -
KT 801

A Tate-Shafarevich twist of a (proper) fibration modifies it by a 1-cocycle of automorphisms given by flows of (holomorphic) vector fields relative to the base, locally in the analytic topology. In general, the total space of a twist does not even have to be homeomorphic to that of the original fibration. Nevertheless, it was conjectured by Saccà that if one started with a Lagrangian fibration of an irreducible hyper-Kähler variety, then the total space of the resulting twist should always be deformation-equivalent to that of the original fibration, provided that it is also algebraic. I will introduce evidence towards this conjecture, including coincidences of certain cohomological invariants, as well as a proof under further topological constraints.

 
January 29, 2026
Analysis [9] Lattice packing of spheres in high dimensions using a stochastically evolving ellipsoid 4:00pm -

We prove that in any dimension n there exists an origin-symmetric ellipsoid of volume c n^2 that contains no points of Z^n other than the origin. Here c > 0 is a universal constant. Equivalently, there exists a lattice sphere packing in R^n whose density is at least c n^2 / 2^n. Previously known constructions of sphere packings in R^n had densities of the order of magnitude of at most n log n / 2^n. Our proof utilizes a stochastically evolving ellipsoid that accumulates at least  c n^2 lattice points on its boundary, while containing no lattice points in its interior except for the origin.

https://yale.zoom.us/j/99948057179 [14]

Quantum Topology and Field Theory [5] A whittled complex for the Khovanov homology of torus braids 4:30pm -
KT 801

We give an algorithm to reduce the number of generators of the Khovanov chain complex of torus braids $(\sigma_1\sigma_2 \dots\sigma_{n−1})^k$ on $n$ strands. I will begin the talk with context on the stable Khovanov homology of torus links leading to the open question of the structure of their homology theory, as well as potential applications to open questions concerning the colored Jones polynomial. Next I will discuss our work, joint with Carmen Caprau, Nicolle Gonzalez, and Radmila Sazdanovic, using Bar-Natan Gaussian elimination, that gives our whittled complex $\mathcal{FT}_n^k$. The whittled complex is homotopy-equivalent to the original Khovanov chain complex but with a reduced number of generators. After sketching the proof, I will end the talk discussing related future projects.

January 30, 2026
Learning seminar on Matroids and Algebraic Cycles [10] Learning seminar on Matroids and Algebraic Cycles 2:15pm -
KT 801

We will have our first introductory and organizational meeting  to study the recent advances where matroids are used to show the failure of the integral Hodge conjecture. 

Learning seminar on Groups, Geometry and Dynamics [6] (Infinite) approximate groups. 4:00pm -
In this talk I will give a brief introduction to approximate groups, with a focus on infinite approximate groups. We will discuss known results in the abelian setting, and a few results about approximate lattices in Lie groups. 
 
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Links
[1] https://calendar.math.yale.edu/list/calendar/grid/week/2025-W52 [2] https://calendar.math.yale.edu/list/calendar/grid/week/2026-W02 [3] https://calendar.math.yale.edu/seminars/special-guest-lecture [4] https://calendar.math.yale.edu/seminars/colloquium [5] https://calendar.math.yale.edu/seminars/quantum-topology-and-field-theory [6] https://calendar.math.yale.edu/seminars/learning-seminar-groups-geometry-and-dynamics [7] https://calendar.math.yale.edu/seminars/geometric-analysis-and-application [8] https://calendar.math.yale.edu/seminars/geometry-symmetry-and-physics [9] https://calendar.math.yale.edu/seminars/analysis [10] https://calendar.math.yale.edu/seminars/learning-seminar-matroids-and-algebraic-cycles [11] https://calendar.math.yale.edu/list/calendar/grid/week/abstract/2025-W52 [12] https://calendar.math.yale.edu/list/calendar/grid/week/abstract/2026-W02 [13] https://yale.zoom.us/j/92334178441?pwd=FmjkR0LeihzxyR7AaNzsvTIPa11tmK.1 [14] https://yale.zoom.us/j/99948057179