Seminars and Colloquia by Series

On Spectral Gap Stability for 2D AKLT Models

Series
Math Physics Seminar
Time
Friday, April 24, 2026 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Amanda YoungUniversity of Illinois Urbana-Champaign

The classification of quantum phases of matter is a fundamental topic in the study of quantum many-body systems. One main question in this study is whether or not there is a nonvanishing spectral gap above the ground state energy and, if so, whether or not this gap is stable under sufficiently short-range perturbations. In their seminal work, Affleck, Kennedy Lieb and Tasaki (AKLT) conjectured the existence of a spectral gap for the model they defined on the hexagonal lattice. Significant evidence supporting this long-standing claim was only recently achieved and naturally leads to the question of whether or not this gap is stable. In this talk, we review this and other recent progress on proving gaps for AKLT models and then turn to the question of whether these gaps are stable. One avenue for establishing gap stability pioneered by Bravyi, Hastings and Michalakis is to prove that the finite volume ground states are sufficiently indistinguishable by local observables in the bulk - a property known as Local Topological Quantum Order. We discuss a forthcoming work which uses cluster expansion techniques to prove that the ground states of the AKLT model on the hexagonal lattice and Lieb lattice satisfy LTQO. This talk is based on joint work with Thomas Andrew Jackson and Bruno Nachtergaele.

Geometry and spectrum of graphs: regularity of the spectral measure

Series
School of Mathematics Colloquium
Time
Thursday, April 23, 2026 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Charles BordenaveInstitut de Mathématiques de Marseille

The spectrum of the discrete Laplacian on a infinite graph, or of its random perturbations such as the Anderson tight-binding model, encodes a rich information about the structure of that space. While natural questions abound (nature of the spectrum, localization of eigenfunctions, behavior of the spectral measure), few admit complete answers outside of very specific cases. In this talk, we will briefly survey some of the main open questions in the area. We will then present an elementary geometric criterion that provides control over the  regularity of the spectral measure.

Sutured annular Khovanov homology and representations of sl_n

Series
Geometry Topology Student Seminar
Time
Wednesday, April 22, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Luis KimGeorgia Tech

The colored Jones polynomial is a quantum knot invariant which can be constructed as a Reshetikhin–Turaev invariant using representations of $U_q(sl_2)$. Khovanov homology categorifies the Jones polynomial and by extension categorifies the representation theory of $sl_2$. Of particular interest is sutured annular Khovanov homology, which admits a structure as an $sl_2$-module. We will discuss a result of Grigsby–Licata–Wehrli that this structure is a representation-theoretic invariant of an annular link. Time permitting, we will discuss some of the structure of this representation, and extend the result to $sl_n$.

Self-Similar Smoothing of A Fluid Boundary Corner

Series
PDE Seminar
Time
Tuesday, April 21, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Speaker
Neel PatelUniversity of Maine

The Hele-Shaw problem describes the dynamics of the boundary of a single fluid in porous media. For the nonzero surface tension case, we provide the first proof (to the best of our knowledge) of the existence of solutions that initially have a corner. The main challenge is the analysis of a nonlocal equation whose linearization has coefficients that grow at infinity.

Quantum Graph States for Graph Theorists

Series
Graph Theory Seminar
Time
Tuesday, April 21, 2026 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Nathan ClaudetUniversity of Innsbruck

Quantum computing is concerned with harnessing the peculiar properties of quantum mechanics, in order to perform information-processing tasks beyond the capabilities of classical computers. Graph states are a family of quantum states, the resources for quantum computers. Graph states exhibit complex forms of quantum entanglement, implying for example that a quantum computer based on graph states is as powerful as any other quantum computer. But, unlike general quantum states, graph states are very easy to describe thanks to their one-to-one correspondence with mathematical graphs. This correspondence implies that many tools from graph theory can be applied to problems in quantum computing.

This talk aims to provide a gentle introduction to graph states, directed toward graph theorists. I will discuss two main applications of graph states, quantum networks and measurement-based quantum computing, and relate these applications to well-known graph-theoretical concepts, in particular vertex-minors. Finally, I will discuss the problem of classifying graph states, and the recent progress achieved through the development of new graph-theoretical tools.

Dynamics of the Nonlinear Schrödinger Equation with an Inverse-Square Potential

Series
PDE Seminar
Time
Tuesday, April 21, 2026 - 14:30 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Xiaoyi Zhang University of Iowa

Please Note: Special time and special room

I will discuss our recent works on the nonlinear Schrodinger equation with an inverse square potential. The primary results include the asymptotic properties of solutions with energy below or equal to the energy of the ground state, as well as the uniqueness of the ground state for the inter-critical problems.

Coulomb Branch Action on Quasimaps to Quiver Varieties via Hall Algebras

Series
Representation Theory, Moduli, and Physics Seminar
Time
Tuesday, April 21, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Tommaso Maria BottaColumbia University

Quiver varieties provide a fundamental bridge between representation theory, enumerative geometry, and physics.  From 3d mirror symmetry, any quiver variety comes with a dual variety known as the Coulomb branch.  A conjecture proposed by Bullimore-Dimofte-Gaiotto-Hilburn-Kim and, independently, Okounkov, asserts that the cohomology of the moduli space of quasimaps to a quiver variety admits a canonical action by the quantized coordinate ring of the dual BFN Coulomb branch.  In this talk, I will report on progress on refining this conjecture and proving it.  The construction relies on a -1 shifted symplectic structure on the moduli space of quasimaps and the theory of cohomological Hall algebras.  Based on work in preparation with Spencer Tamagni.

Multiscale-Multiphysics Phenomena in Complex Fluids: The Energetic Variational Approaches

Series
Applied and Computational Mathematics Seminar
Time
Monday, April 20, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/94954654170
Speaker
Chun LiuIllinois Institute of Technology

Complex fluids are abundant in our daily life. Unlike traditional solids, liquids and the diluted solutions, the model equations for complex fluids continue to evolve with the new experimental evidences and emerging applications. Most of these important properties are due to the coupling and competition between effects from different scales or even from different physical origins/principles. The energetic variational approaches (EnVarA), motivated by the seminal works of Onsager and Rayleigh, are designed to study such systems. In this talk, I will discuss several complex fluid systems, and the associated mathematical issues.

S^1-actions on Moduli Spaces

Series
Geometry Topology Seminar
Time
Monday, April 20, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jiajun YanRice University

Moduli spaces are central objects in modern topology and geometry, serving as powerful tools for extracting invariants from underlying manifolds. Gauge theory provides a prolific source of such spaces, utilizing techniques from geometry, analysis, and algebra to probe their structure. In this talk, we survey key gauge-theoretic moduli spaces with an emphasis on how $S^1$-actions can be used to study their topological properties. In particular, we apply these methods to hyperkähler ALE spaces, discussing their applications to the McKay correspondence and symplectic and contact homologies.

Local cohomology with support in Schubert varieties of the Grassmannian

Series
Algebra Seminar
Time
Monday, April 20, 2026 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Mike PerlmanUniversity of Alabama

Please Note: There will be a pre-seminar at 10:55-11:25 in Skiles 005.

Given a closed subvariety Z in a smooth complex variety X, the local cohomology sheaves with support in Z are holonomic D-modules, and thus have finite filtration with simple composition factors. We determine the D-module structure on local cohomology in the case when X is a Grassmannian and Z is a Schubert variety, including a combinatorial formula describing the composition factors and the weight filtration in the sense of mixed Hodge modules. Upon restriction to the opposite big cell, these calculations recover several previously known results concerning local cohomology with support in determinantal varieties.

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