Week of November 12, 2023

Mon Nov 13, 2023
4:00pm to 5:00pm - RH 306 - Applied and Computational Mathematics
Xinwei Yu - (University of Alberta)
Some new regularity criterions for the 3D incompressible Navier-Stokes equations

In this talk we discuss several regularity criterions for the 3D incompressible Navier-Stokes equations, including several new classes of Prodi-Serrin type criterions, as well as a new type of geometrical conditions on the super level set of the velocity magnitude that guarantees regularity. This is a ummary of joint work in recent years with Prof. Chuong V. Tran of the University of St. Andrews, Scotland, and Mr. Benjamin Pineau of the University of Alberta (Now at UC Berkeley).

4:00pm - RH 340N - Geometry and Topology
Jiawei Zhou - (BIMSA, Beijing)
On the formality of sphere bundles

A manifold is called formal if it has the same rational homotopy type
as the cohomology ring. We first consider the formality of a sphere bundle
over a formal manifold. In this case the formality is entirely determined by
the Bianchi-Massey tensor, which is a 4-tensor on a subspace of the
cohomology ring, introduced by Crowley and Nordstrom. As a special case, we
will see that if a manifold and its unit tangent bundle are both formal,
then the manifold has either Euler characteristic zero or rational
cohomology ring generated by one element. Finally we discuss the case of
a general base manifold, and give an obstruction to formality.

4:00pm to 5:30pm - RH 306P - Logic Set Theory
Aaron Anderson - (UCLA)
Distality in continuous logic

We examine distal theories and structures in the context of continuous logic, providing several equivalent definitions.

By studying the combinatorics of fuzzy VC-classes, we find continuous versions of (strong) honest definitions and distal cell decompositions.

By studying generically stable Keisler measures in continuous logic, we apply the theory of continuous distality to analytic versions of graph regularity.

We will also present some examples of distal metric structures, including dual linear continua and a continuous version of o-minimality.

Tue Nov 14, 2023
3:00pm to 3:50pm - RH306 - Analysis
Ziming Shi - (UCI)
½ estimate for global Newlander-Nirenberg theorem on strongly pseudoconvex domains

Given a formally integrable almost complex structure $X$ defined on the closure of a bounded domain $D \subset \mathbb C^n$, and provided that $X$ is sufficiently close to the standard complex structure, the global Newlander-Nirenberg problem asks whether there exists a global diffeomorphism defined on $\overline D$ that transforms $X$ into the standard complex structure, under certain geometric and regularity assumptions on $D$. In this talk I will present my recent result on the ½ estimate for global Newlander-Nirenberg problem on strongly pseudoconvex domains. The main ingredients in our proof are the construction of Moser-type smoothing operators on bounded Lipschitz domains using Littlewood-Paley theory and a convergence scheme of KAM type. 

4:00pm to 5:00pm - ISEB 1200 - Differential Geometry
Junsheng Zhang - (UC Berkeley)
On complete Calabi-Yau manifolds asymptotic to cones

We proved a ``no semistability at infinity" result for complete Calabi-Yau metrics asymptotic to cones, by eliminating the possible appearance of an intermediate K-semistable cone in the 2-step degeneration theory developed by Donaldson-Sun. As a consequence, a classification result for complete Calabi-Yau manifolds with Euclidean volume growth and quadratic curvature decay is given. Moreover a byproduct of the proof is a polynomial convergence rate  to the asymptotic cone for such manifolds. Joint work with Song Sun.

 

Wed Nov 15, 2023
2:00pm to 3:00pm - 510R Rowland Hall - Combinatorics and Probability
Gil Goffer - (UCSD)
Probabilistic laws on infinite groups

In various cases, a law that holds in a group with high probability, must actually hold for all elements. For instance, a finite group in which the commutator law [x,y]=1 holds with probability at least 5/8, must be abelian. For infinite groups, one needs to work a bit harder to define the probability that a given law holds. One natural way is by sampling a random element uniformly from the r-ball in the Cayley graph and taking r to infinity; another way is by sampling elements using random walks. It was asked by Amir, Blachar, Gerasimova, and Kozma whether a law that holds with probability 1, must actually hold globally, for all elements. In a recent joint work with Be’eri Greenfeld, we give a negative answer to their question.

In this talk I will give an introduction to probabilistic group laws and present a finitely generated group that satisfies the law x^p=1 with probability 1, but yet admits no group law that holds for all elements.

Thu Nov 16, 2023
9:00am to 10:00am - Zoom - Inverse Problems
Emilia Blåsten - (LUT University)
Scattering from corners and other singularities

https://sites.uci.edu/inverse/

Fri Nov 17, 2023
1:00pm - - Graduate Seminar
Jesse Wolfson - (UC Irvine)
Mathematics and Africanist Dance

Abstract: For over a decade, I have had the privilege to collaborate and learn from internationally acclaimed, Brooklyn-based choreographer Reggie Wilson and his Fist and Heel Performance Group https://www.fistandheelperformancegroup.org/ .  This engagement has given me new practices for teaching and mentoring, widened my sense of where and how mathematical knowledge is held, and surfaced unexplored areas near the heart of mainstream geometry and topology. In this short talk, I'll try to give a quick sense of how this came about, what it's taught me about being a mathematician, and why I think dance and bodies have more to teach us mathematically.

4:00pm to 4:50pm - 440R - Nonlinear PDEs
Yang Yang - (Johns Hopkins University)
A Bernstein theorem for anisotropic minimal graphs with controlled growth

Parametric elliptic functionals are natural generalizations of the area functional that both arise in many applications and offer important technical challenges. Given any parametric elliptic functional, the anisotropic Bernstein problem asks whether the entire anisotropic minimal graphs associated to the functional in R^{n+1} are necessarily hyperplanes. A recent breakthrough regarding this problem indicates that the answer is positive if and only if n < 4. In this talk, we will talk about a Bernstein result for entire anisotropic minimal graphs in all dimensional Euclidean spaces, under assuming some certain growth condition on the anisotropic minimal graphs and C^3-closeness between anisotropic area integrands and the classical area integrand. This is joint work with W. Du.