# UC San Diego Analysis Seminar

## 2022-2023

Time Location Organizers
Tuesdays at 11am Hybrid format

In-person talks in AP & M 7321,

Remote talks on Zoom, contact organizers for Zoom details

Ioan Bejenaru and Mohandas Pillai

### Fall 2022

Date Speaker Title + Abstract
October 18

Sebastian Herr

Bielefeld University

Global wellposedness of the Zakharov System below the ground state

The Zakharov system is a quadratically coupled system of a Schrödinger and a wave equation, which is related to the focussing cubic Schrödinger equation. We consider the associated Cauchy problem in the energy-critical dimension d=4 and prove that it is globally well-posed in the full (non-radial) energy space for any initial data with energy and wave mass below the ground state threshold. The result is based on a uniform Strichartz estimate for the Schrödinger equation with potentials solving the wave equation. A key ingredient in the non-radial setting is a bilinear Fourier extension estimate. This is joint work with Timothy Candy and Kenji Nakanishi.

November 4

4 PM

APM 6402

Note the unusual day, time, location

Dallas Albritton

Princeton

Title and Abstract
November 15

Kihyun Kim

IHES

Rigidity of long-term dynamics for the self-dual Chern-Simons-Schrödinger equation within equivariance

We consider the long time dynamics for the self-dual Chern-Simons-Schrödinger equation (CSS) within equivariant symmetry. Being a gauged 2D cubic nonlinear Schrödinger equation (NLS), (CSS) is L2-critical and has pseudoconformal invariance and solitons. However, there are two distinguished features of (CSS), the self-duality and non-locality, which make the long time dynamics of (CSS) surprisingly rigid. For instance, (i) any finite energy solutions to (CSS) decomposes into at most one(!) modulated soliton and a radiation. Moreover, (ii) in the high equivariance case (i.e., the equivariance index ≥ 1), any smooth finite-time blow-up solutions even have a universal blow-up speed, namely, the pseudoconformal one. We explore this rigid dynamics using modulation analysis, combined with the self-duality and non-locality of the problem.

November 17

3-4 PM

APM 7218

Note the unusual day, time, location

Jan Slovak

Masaryk U

Nearly invariant calculus for a few CR (and all parabolic) geometries

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November 29

Manuel Del Pino

University of Bath

DYNAMICS OF CONCENTRATED VORTICITIES IN 2D AND 3D EULER FLOWS

Abstract

December 6

Brown University

Stability of a point charge for the repulsive Vlasov-Poisson system

We consider solutions of the repulsive Vlasov-Poisson system which are a combination of a point charge and a small density with respect to Liouville measure (a cloud''), and we show that these solutions exist globally, that the electric field decays at an optimal rate and that the particle distribution converges along a modified scattering dynamics. This follows by a Lagrangian study of the linearized equation, which is integrated by means of an asymptotic action-angle coordinate transformation, and an Eulerian study of the nonlinear dynamic which exhibits the mixing'' mechanism responsible for the asymptotic behavior. This is joint work with Klaus Widmayer (U. Zurich) and Jiaqi Yang (ICERM).

December 6

3-4 PM

APM 5402

Note the unusual time, location

Nordine Mir

Texas A&M University at Qatar

Finite jet determination of CR maps into real-algebraic sets

We present recent results about finite jet determination of CR maps of positive codimension from real-analytic CR manifolds into real-algebraic subsets in complex space, or more generally Nash subsets. One instance of such results is the unique jet determination of germs of CR maps from minimal real-analytic CR submanifolds in $\C^N$ into Nash subsets in $\C^{N'}$ of D'Angelo finite type, for arbitrary $N,N'\geq 2$. This is joint work with B. Lamel.

### Winter 2023

Date Speaker Title + Abstract

January 18

2 pm

Note the unusual day, time

Linfeng Lin

USC

On the local existence of solutions to the Navier-Stokes-wave system with a free interface

We address a system of equations modeling a compressible fluid interacting with an elastic body in dimension three. We prove the local existence and uniqueness of a strong solution when the initial velocity belongs to the space $H^{2+\epsilon}$ and the initial structure velocity is in $H^{1.5+\epsilon}$, where $\epsilon\in(0,1/2)$.

February 7

In-person

AP & M 7321

University of Tennessee, Knoxville

Variational Analysis of some nonlocal functionals and associated function spaces

I will present a recent work on variational problems involving nonlocal energy functionals that appear in nonlocal mechanics. The well-posedness of variational problems is established via a careful study of the associated energy spaces, which are nonstandard. I will discuss some difficulties in proving fundamental structural properties of the function spaces such as compactness. For a sequence of parametrized nonlocal functionals in suitable form, we compute their variational limit and establish a rigorous connection with classical models.

February 28

In-person

AP & M 7321

Javier Cueto

A framework for variational problems based on nonlocal gradients on bounded domains inspired by Peridynamics

Inspired by the rise on the interest for nonlocal models, mainly Peridynamics, we decided to study a functional framework suitable for (variational) nonlocal models, such as that of nonlocal hyperelasticity. This has lead to a nonlocal framework based on truncated fractional gradients (i.e. nonlocal gradients with a fractional singularity defined over bounded domains), in which continuous and compact embeddings and, in particular, nonlocal Poincaré inqualities has been obtained thanks to a nonlocal version of the fundamental theorem of calculus. As a consequence, the existence of minimizers of nonlocal polyconvex vectorial functionals is obtained, and more recently quasiconvex functionals. Some of these last results have been obtained from a result that relates nonlocal gradients with classical ones and vice-versa. These results are accompanied by a study of the localization (recovering of the classical model) when s goes to 1 (actually, continuity on s with s being the fractional index of differentiability).

March 14

Zoom

Jacek Jendrej

Sorbonne Paris Nord

Bubble decomposition for the harmonic map heat flow in the equivariant case

I will present a recent joint work with Andrew Lawrie from MIT. We consider the harmonic map heat flow for maps from the plane R^2 to the sphere S^2, under the so-called equivariant symmetry. It is known that solutions to the initial value problem exhibit bubbling along a sequence of times - the solution decouples into a superposition of harmonic maps concentrating at different scales and a body map that accounts for the rest of the energy. We prove that this bubble decomposition occurs continuously in time. The main new ingredient in the proof is the notion of a collision interval motivated by our recent work on the soliton resolution problem for equivariant wave maps.

### Spring 2023

Date Speaker Title + Abstract
April 11

Shi-Zhuo Looi

UC Berkeley

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