Group Actions and Dynamics [3] | Properness criteria for affine actions of Anosov groups |
4:00pm -
KT 207
|
I will present some criteria (necessary or sufficient) for the action on the affine space of a group Gamma of affine transformations to be proper. This is joint work with Fanny Kassel. The main of these criteria links properness of action to the divergence of a parameter called the Margulis invariant. This invariant measures roughly the translation part of an affine transformation, but in a way that is invariant by conjugation. This link was already known in some special cases (and has often been exploited to construct proper actions). We tried to establish it in as general setting as possible. We proved it in particular if Gamma has some suitable Anosov property (with respect to some natural parabolic subgroup, that depends on the affine group we are working in). I will possibly also evoke some other invariants similar to the Margulis invariant, that could lead to criteria that work in even more general settings. |
Analysis [4] | Spectral theory of high-contrast random media |
4:00pm -
KT 205
|
The talk is concerned with the rigorous mathematical description of propagation and localisation of waves in a particular class of composite materials with random microscopic geometry, called micro-resonant (or high-contrast) random media: small inclusions of a “soft” material are randomly dispersed in a “stiff” matrix. The highly contrasting physical properties of the two constituents, combined with a particular scaling of the inclusions, result in microscopic resonances, which manifest macroscopically by allowing propagation of waves in the material only within certain ranges of frequencies (band-gap spectrum). High-contrast media with periodically distributed inclusions have been extensively studied and numerous results are available in the literature. However, their stochastic counterparts, which model more realistic scenarios and may exhibit localisation, are far from being well understood from a mathematical viewpoint. In my talk I will give an overview of existing results through the prism of stochastic homogenisation and spectral theory, and discuss recent advances and ongoing work. Based on joint works with M. Cherdantsev, I. Velčić, P. Bella and M. Täufer. |
Geometry & Topology [5] | A ``cubist'' decomposition of the Handel-Mosher axis bundle & the conjugacy problem for Out(F_r) |
4:00pm -
KT 207
|
Outer automorphisms of free groups are largely studied via their action on Culler-Vogtmann Outer space. However, unlike in hyperbolic space or Teichmuller space (surface) settings, the dynamically minimal (fully irreducible) free group outer automorphisms act on Culler-Vogtmann Outer space with a collection of axes, whose closure is the Handel-Mosher ``axis bundle.'' Not much of the structure of this axis bundle has yet been understood. Together with Chi Cheuk Tsang, we prove that the axis bundle has a "cubist" structure and use this structure to find preferred axes for these outer automorphisms. We then use these axes to provide a solution to the fully irreducible conjugacy problem. This work can be seen as in analogy with that of Hamenstadt and Agol in the surface setting. |
Robinson Lectures [6] | Bass-Note Spectra of locally uniform geometries | 4:00pm - |
We formulate and report on the problem of the Bass-Note Spectrum of an invariant operator as one varies over locally uniform geometries. In the Euclidean setting this recasts classical problems of Mahler from the geometry of numbers in a new light. For certain operators homogeneous dynamics can be used decisively. In the non-Euclidea setting of hyperbolic manifolds we review some recent developments using the conformal bootstrap method and of random covers to study the Bass- Note spectra. We highlight the theme and impact of rigidity. |
Quantum Topology and Field Theory [7] | Jordan Blocks of the Quantum Monodromy |
4:30pm -
KT 801
|
The small quantum connection of a Fano variety is among the most accessible and fundamental objects in enumerative geometry. In this talk, I’ll survey recent results on the structure of the quantum connection, with an emphasis on bounds for the sizes of Jordan blocks of the “regularized monodromy”. These bounds can be viewed as mirror analogues of classical results by Borel, Katz, and Varchenko concerning the Jordan blocks of monodromy for Gauss–Manin connections associated to families of varieties. This is joint work—partially in progress—with P. Seidel. |
Friday Morning Seminar [8] | TBA |
10:00am -
KT 801
|
A relaxed-pace seminar on impromptu subjects related to the interests of the audience. Everyone is welcome. The subjects are geometry, probability, combinatorics, dynamics, and more! |
Algebra and Geometry lecture series [9] | Vertex algebra and moduli of Higgs bundles III |
3:00pm -
KT801
|
Sam will discuss the connection between VOA and the cohomology of the Hitchin moduli space, as a continuation of his first 2 lectures. |
Links
[1] https://math.yale.edu/list/calendar/grid/week/abstract/2025-W15
[2] https://math.yale.edu/list/calendar/grid/week/abstract/2025-W17
[3] https://math.yale.edu/seminars/group-actions-and-dynamics
[4] https://math.yale.edu/seminars/analysis
[5] https://math.yale.edu/seminars/geometry-topology
[6] https://math.yale.edu/seminars/robinson-lectures
[7] https://math.yale.edu/seminars/quantum-topology-and-field-theory
[8] https://math.yale.edu/seminars/friday-morning-seminar
[9] https://math.yale.edu/seminars/algebra-and-geometry-lecture-series