Date/Time : 08 Jul 2026 15:00
Venue : S17 #05-11 (Seminar Room 5)
Speaker : Wen Qi Zhang, Australian National University

It is known that $L^1$ Sobolev and Stein-Weiss inequalities follow a slightly different pattern to their $L^p$ counterparts. For instance, they serve as weaker replacement inequalities for the failure of $L^1$ inequalities between differential operators. Recent work by P. De Napoli and T. Picon has shown that the canceling/cocanceling framework introduced by J. Van Schaftingen can be used to extend the $L^1$ Stein-Weiss inequalities beyond their expected range. Inspired by these ideas, we investigate if the cocanceling constraint can be weakened in a subcritical setting, and we also explore how one may further extend these inequalities to a critical case.

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Date/Time : 07 Jul 2026 11:00
Venue : S17 #04-05 (Seminar Room 2)
Speaker : Weiren Zhao , NYU Abu Dhabi

In this talk, I will talk about the long-time behavior of solutions to the two-dimensional Navier–Stokes equations with initial data evolving under the influence of the planar Couette flow. We focus on general perturbations, which may be large and of low regularity, and show that the vorticity asymptotically approaches a constant multiple of the fundamental solution of the corresponding linearized vorticity equation after a long-time evolution determined by the relative Reynolds number.

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Date/Time : 05 May 2026 15:00
Venue : S17 #04-05 (Seminar Room 2)
Speaker : Yu-Sen An (Nanjing University of Aeronautics and Astronautics), Yu-Sen An (Nanjing University of Aeronautics and Astronautics)

With the detection of gravitational waves and the release of black hole shadow images, black hole becomes a real astrophysical object instead of a mere mathematical artifact. However, while extensive works have been done on the black hole exterior, the interior region remains far less explored. Thus in this talk, I will focus on the black hole interior structure, from the horizon down to the singularity. We are particularly interested in the black hole spacetime in anti–de Sitter (AdS) space since this can be connected to quantum many body systems through holographic duality. I will show that the interior dynamics are far richer than previously expected. I will choose several important holographic models such as holographic superconductor to illustrate these distinct behaviors. Finally, I will demonstrate how to connect these interior structures to the boundary physics, potentially revealing new aspects of holographic duality.

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Date/Time : 05 May 2026 16:00
Venue : S17 #04-05 (Seminar Room 2)
Speaker : Nguyen Thac Dung, Hanoi University of Sciences, (VNU)

It is well-known that the Bochner technique is very useful to study geometry and topology of Riemannian manifolds. In this talk, I mention a new theory about curvature conditions related to the Bochner techniques following recent works by Petersen and Wink. I also introduce their applications on compact manifolds. Then, I will extend their results on non-compact complete Riemannian manifolds and prove some vanishing and rigidity results.

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Date/Time : 22 Apr 2026 14:00
Venue : S17 #04-06 (Seminar Room 1)
Speaker : Jia Shi, Indiana University Bloomington

In this talk, I will introduce the implosion blow-up results for the compressible Euler, the compressible Navier-Stokes equations, and the defocusing nonlinear Schrödinger equation. We will discuss the existence of self-similar solutions and the stability near those solutions. During the talk, I will mention our work with Gonzalo Cao-Labora, Javier Gómez-Serrano, and Gigliola Staffilani on the first non-radial implosion result for those three equations. If there is time, I will also mention our work on self-similar solutions of a hydrodynamic equation that may formally arise as potential blow-up profiles of the focusing NLS equation.

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Date/Time : 22 Apr 2026 15:00
Venue : S17 #04-06 (Seminar Room 1)
Speaker : Khakim Egamberganov, National University of Singapore

We study the long-time behaviour of vorticity in three-dimensional axisymmetric Euler flows without swirl. This equation is globally well-posed when the initial vorticity satisfies some integrability conditions, but due to the presence of vortex stretching term, the vorticity and related quantities tend to grow in time. In this talk, we will discuss some improved upper and lower bounds for vorticity growth. This talk is based on joint work with Yao Yao.

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Date/Time : 18 Mar 2026 14:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Zihui Zhao, Johns Hopkins University

Free boundary problems are problems of solving an elliptic or parabolic PDE, but on a domain that is determined by the solution, and they arise naturally in the study of water waves and ice melting, etc. In this talk, we will focus on the regularity of the free boundaries for the Bernoulli problem, firstly studied by Alt and Caffarelli. More precisely, we study the behavior of such solutions near some well-known singularity models. In particular, our result implies that such singularity is not the typical behavior. This is joint work with Engelstein and Restrepo.

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Date/Time : 18 Mar 2026 16:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Sam G. Krupa, École Normale Supérieure, Paris

For hyperbolic systems of conservation laws in 1-D, fundamental questions about uniqueness and blow up of weak solutions still remain even for the apparently “simple” systems of two conserved quantities such as isentropic Euler and the p-system. Similarly, in the multi-dimensional case, a longstanding open question has been the uniqueness of weak solutions with initial data corresponding to the compressible vortex sheet. We address all of these questions by using the lens of convex integration, a general method of constructing highly irregular and non-unique solutions to PDEs. Our proofs involve computer-assistance. This talk is based on joint work with László Székelyhidi, Jr.

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Date/Time : 11 Mar 2026 15:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Georg Weiss, University of Duisburg-Essen

While global solutions of the obstacle problem have recently been completely characterized (Eberle-Figalli-Weiss 2025), the class of global solutions to the Bernoulli problem is, by a result of M. Traizet (2013), much richer and closely related to minimal surfaces.

In this talk, we explain why a frequency formula of the type used in the obstacle problem is unlikely to be valid for the Bernoulli problem. We also present progress on a different approach—one that does not rely on complex analysis—which appears to be a promising alternative for studying global solutions of the Bernoulli problem.

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