Fall 2023 Analysis Seminar

Organizer: Shaoming Guo

Email: shaomingguo (at) math (dot) wisc (dot) edu

Time: Wed 3:30--4:30

Room: B223

We also have room B211 reserved at 4:25-5:25 for discussions after talks.

All talks will be in-person unless otherwise specified.

In some cases the seminar may be scheduled at different time to accommodate speakers.

If you would like to subscribe to the Analysis seminar list, send a blank email to analysis+join (at) g-groups (dot) wisc (dot) edu

Week	Date	Speaker	Institution	Title	Host(s)	Notes (e.g. unusual room/day/time)
1	We, Sep. 6
	Fr, Sept. 8	Tushar Das	UW La Crosse	Playing games on fractals: Dynamical and Diophantine	Betsy	Colloquium, 4-5pm in B239
2	Tu, Sept. 12	Rajula Srivastava	Hausdorff Center of Mathematics, Bonn	Counting Rational Points near Flat Hypersurfaces	Andreas	Tuesday 4:00 pm in VV B135
	We, Sept. 13	Niclas Technau	University of Graz	Oscillatory Integrals Count	Andreas
3	We, Sept. 20	Terry Harris	UW Madison	Horizontal Besicovitch sets of measure zero and some related problems	analysis group
4	We, Sept. 27
5	Mo, Oct 2	Edriss Titi	Texas A&M	On the Solvability of the Navier-Stokes and Euler Equations, where do we stand?	Leslie and Sam	Distinguished Lecture 1 (general audience talk), 4-5pm in B239
5	Tu, Oct 3	Edriss Titi	Texas A&M	Oceanic and Atmospheric Dynamics Models - Global Regularity and Finite-time Singularity.	Leslie and Sam	Distinguished Lecture 2 (Analysis seminar), 4-5pm, B135
5	We, Oct 4	Edriss Titi	Texas A&M	Downscaling Data Assimilation Algorithm for Weather and Climate Prediction	Leslie and Sam	Distinguished Lecture 3 (Applied and Computational math seminar), 901
5	We, Oct. 4	Tristan Leger	Princeton	L^p bounds for spectral projectors on hyperbolic surfaces	Simon
6	We, Oct. 11	Bingyang Hu	Auburn	On the curved Trilinear Hilbert transform	Brian
7	We, Oct. 18	Ashley Zhang	Vanderbilt	Convergence of discrete non-linear Fourier transform via spectral problems for canonical systems	Alexei
8	Tu, Oct 25	Gigliola Staffilani	MIT	(See Colloquium page)	Miahela and Leslie	Hilldale Lecture 4-5pm in 1310 Sterling Hall
8	We, Oct. 25	Gigliola Staffilani	MIT	(See Colloquium page)	Mihaela and Leslie	Special Colloquium 4-5pm in B239
	Fr, Oct 27	Rodrigo Bañuelos	Purdue	Probabilistic tools in discrete harmonic analysis	Betsy	Colloquium, 4-5pm in B239
9	We, Nov. 1	Tent scheduled distinguished lecture				Distinguished lecture 4-5pm in B239
10	We, Nov. 8	Lechao Xiao	Google deepmind		Shaoming
11	We, Nov. 15	Neeraja Kulkarni	Caltech		Jacob
12	We, Nov. 22	No talk	No talk		No talk	Thanksgiving week
13	We, Nov. 29	Changkeun Oh	MIT		Shaoming
14	We, Dec. 6
15	We, Dec. 13	Jing-Jing Huang	Nevada		Shaoming
1	We, Jan. 24, 2024
2	We, Jan. 31
3	We, Feb. 7	Donald Stull	University of Chicago		Betsy, Shaoming, and Jake F.
4	We, Feb. 14
5	We, Feb. 21
6	We, Feb. 28	Alex Rutar	University of St. Andrews		Andreas
7	We, Mar. 6	Song-Ying Li	UC-Irvine		Xianghong
8	We, Mar. 13
9	We, Mar. 20
	Fr, Mar. 22	Jack Lutz	Iowa State University		Shaoming	department colloquium, 4-5pm
10	We, Mar. 27	Spring recess	spring recess		spring recess
11	We, Apr. 3
12	We, Apr. 10	Victor Bailey	University of Oklahoma		Betsy
13	We, Apr. 17
14	We, Apr. 24
15	We, May 1

Abstracts

Tushar Das

Title: Playing games on fractals: Dynamical & Diophantine

Abstract: We will present sketches of a program, developed in collaboration with Lior Fishman, David Simmons, and Mariusz Urbanski, which extends the parametric geometry of numbers (initiated by Wolfgang Schmidt and Leonhard Summerer) to Diophantine approximation for systems of m linear forms in n variables. Our variational principle (arXiv:1901.06602) provides a unified framework to compute Hausdorff and packing dimensions of a variety of sets of number-theoretic interest,  as well as their dynamical counterparts via the Dani correspondence. Highlights include the introduction of certain combinatorial objects that we call templates, which arise from a dynamical study of Minkowski’s successive minima in the geometry of numbers; as well as a new variant of Schmidt’s game designed to compute the Hausdorff and packing dimensions of any set in a doubling metric space. The talk will be accessible to students and faculty whose interests contain a convex combination of homogeneous dynamics, Diophantine approximation and fractal geometry.

Rajula Srivastava

Title: Counting Rational Points near Flat Hypersurfaces

Abstract: How many rational points with denominator of a given size lie within a given distance from a compact hypersurface? In this talk, we shall describe how the geometry of the surface plays a key role in determining this count, and present a heuristic for the same. In a recent breakthrough, J.J. Huang proved that this guess is indeed true for hypersurfaces with non-vanishing Gaussian curvature. What about hypersurfaces with curvature only vanishing up to a finite order, at a single point? We shall offer a new heuristic in this regime which also incorporates the contribution arising from "local flatness". Further, we will describe how ideas from Harmonic Analysis can be used to establish the indicated estimates for hypersurfaces of this type immersed by homogeneous functions. In particular, we shall use a powerful bootstrapping argument relying on Poisson summation, duality between flat and "rough" hypersurfaces, and the method of stationary phase. A crucial role is played by a dyadic scaling argument exploiting the homogeneous nature of the hypersurface. Based on joint work with N. Technau.

Niclas Technau

Title: Oscillatory Integrals Count

Abstract: This talk is about phrasing (number theoretic) counting problems in terms oscillatory integrals. We shall provide a simple introduction to the topic, mention open questions, and report on joint work with Sam Chow, as well as on joint work with Chris Lutsko.

Terry Harris

Title: Horizontal Besicovitch sets of measure zero and some related problems

Abstract: It is shown that horizontal Besicovitch sets of measure zero exist in R^3. The proof is constructive and uses point-line duality analogously to Kahane’s construction of measure zero Besicovitch sets in the plane. Some consequences and related examples are shown for the SL_2 Kakeya maximal function.

Tristan Leger

Title: L^p bounds for spectral projectors on hyperbolic surfaces

Abstract: In this talk I will present L^p boundedness results for spectral projectors on hyperbolic surfaces. I will focus on the case where the spectral window has small width. Indeed the negative curvature assumption leads to improvements over the universal bounds of C.Sogge, thus illustrating how these objects are sensitive to the global geometry of the underlying manifold. I will also explain how this relates to the general theme of delocalization of eigenfunctions of the Laplacian on hyperbolic surfaces. This is based on joint work with Jean-Philippe Anker and Pierre Germain.

Bingyang Hu

Title: On the curved Trilinear Hilbert transform

Abstract: The goal of this talk is to discuss the Lp boundedness of the trilinear Hilbert transform along the moment curve. More precisely, we show that the operator $$ H_C(f_1, f_2, f_3)(x):=p.v. \int_{\mathbb R} f_1(x-t)f_2(x+t^2)f_3(x+t^3) \frac{dt}{t}, \quad x \in \mathbb R $$ is bounded from $L^{p_1}(\mathbb R) \times L^{p_2}(\mathbb R) \times L^{p_3}(\mathbb R}$ into $L^r(\mathbb R)$ within the Banach H\"older range $\frac{1}{p_1}+\frac{1}{p_2}+\frac{1}{p_3}=\frac{1}{r}$ with $1<p_1, p_3<\infty$, $1<p_2 \le \infty$ and $1 \le r <\infty$.

The main difficulty in approaching this problem(compared to the classical approach to the bilinear Hilbert transform) is the lack of absolute summability after we apply the time-frequency discretization(which is known as the LGC-methodology introduced by V. Lie in 2019). To overcome such a difficulty, we develop a new, versatile approch -- referred to as Rank II LGC (which is also motived by the study of the non-resonant bilinear Hilbert-Carleson operator by C. Benea, F. Bernicot, V. Lie, and V. Vitturi in 2022), whose control is achieved via the following interdependent elements:

1). a sparse-uniform deomposition of the input functions adapted to an appropriate time-frequency foliation of the phase-space;

2). a structural analysis of suitable maximal "joint Fourier coefficients";

3). a level set analysis with respect to the time-frequency correlation set.

This is a joint work with my postdoc advisor Victor Lie from Purdue.

Links to previous seminars

Rodrigo Bañuelos

Title: Probabilistic tools in discrete harmonic analysis

Abstract: The discrete Hilbert transform was introduced by David Hilbert at the beginning of the 20th century as an example of a singular quadratic form. Its boundedness on the space of square summable sequences appeared in H. Weyl’s doctoral dissertation (under Hilbert) in 1908. In 1925, M. Riesz proved that the continuous version of this operator is bounded on L^p(R), 1 < p < \infty, and that the same holds for the discrete version on the integers. Shortly thereafter (1926), E. C. Titchmarsh gave a different proof and from it concluded that the operators have the same p-norm. Unfortunately, Titchmarsh’s argument for equality was incorrect. The question of equality of the norms had been a “simple tantalizing" problem ever since.

In this general colloquium talk the speaker will discuss a probabilistic construction, based on Doob’s “h-Brownian motion," that leads to sharp inequalities for a collection of discrete operators on the d-dimensional lattice Z^d, d ≥ 1. The case d = 1 verifies equality of the norms for the discrete and continuous Hilbert transforms. The case d > 1 leads to similar questions and conjectures for other Calderón-Zygmund singular integrals in higher dimensions.