Difference between revisions of "Analysis Seminar"
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Abstract: Let <math>Q(X)</math> be any integral primitive positive definite quadratic form in <math>k</math> variables, where <math>k\geq4</math>, and discriminant <math>D</math>. For any integer <math>n</math>, we give an upper bound on the number of integral solutions of <math>Q(X)=n</math> in terms of <math>n</math>, <math>k</math>, and <math>D</math>. As a corollary, we prove a conjecture of Lester and Rudnick on the small scale equidistribution of almost all functions belonging to any orthonormal basis of a given eigenspace of the Laplacian on the flat torus <math>\mathbb{T}^d</math> for <math>d\geq 5</math>. This conjecture is motivated by the work of Berry\cite{Berry, Michael} on semiclassical eigenfunction hypothesis. | Abstract: Let <math>Q(X)</math> be any integral primitive positive definite quadratic form in <math>k</math> variables, where <math>k\geq4</math>, and discriminant <math>D</math>. For any integer <math>n</math>, we give an upper bound on the number of integral solutions of <math>Q(X)=n</math> in terms of <math>n</math>, <math>k</math>, and <math>D</math>. As a corollary, we prove a conjecture of Lester and Rudnick on the small scale equidistribution of almost all functions belonging to any orthonormal basis of a given eigenspace of the Laplacian on the flat torus <math>\mathbb{T}^d</math> for <math>d\geq 5</math>. This conjecture is motivated by the work of Berry\cite{Berry, Michael} on semiclassical eigenfunction hypothesis. | ||
+ | |||
+ | ===Dong Dong=== | ||
+ | |||
+ | Title: Hibert transforms in a 3 by 3 matrix and applications in number theory | ||
+ | |||
+ | Abstract: This talk could interest both analysts and number theorists. I will first present 35 variants of Hilbert transforms, with a focus on their connections with ergodic theory, number theory, and combinatorics. Then I will show how to use Fourier analysis tools to reduce a number theory problem (Roth theorem) to an algebraic geometry problem: this joint work Li and Sawin fully answers a question of Bourgain and Chang about three-term polynomial progressions in subsets of finite fields. I guarantee that a second-year graduate student can understand at least 50% of the talk. | ||
=Extras= | =Extras= | ||
[[Blank Analysis Seminar Template]] | [[Blank Analysis Seminar Template]] |
Revision as of 14:41, 29 October 2017
Analysis Seminar
The seminar will meet Tuesdays, 4:00 p.m. in VV B139, unless otherwise indicated.
If you wish to invite a speaker please contact Betsy at stovall(at)math
Previous Analysis seminars
2017-2018 Analysis Seminar Schedule
date | speaker | institution | title | host(s) |
---|---|---|---|---|
September 8 in B239 | Tess Anderson | UW Madison | A Spherical Maximal Function along the Primes | Tonghai |
September 19 | Brian Street | UW Madison | Convenient Coordinates | Betsy |
September 26 | Hiroyoshi Mitake | Hiroshima University | Derivation of multi-layered interface system and its application | Hung |
October 3 | Joris Roos | UW Madison | A polynomial Roth theorem on the real line | Betsy |
October 10 | Michael Greenblatt | UI Chicago | Maximal averages and Radon transforms for two-dimensional hypersurfaces | Andreas |
October 17 | David Beltran | Basque Center of Applied Mathematics | Fefferman-Stein inequalities | Andreas |
Wednesday, October 18, 4:00 p.m. in B131 | Jonathan Hickman | University of Chicago | Factorising X^n | Andreas |
October 24 | Xiaochun Li | UIUC | Recent progress on the pointwise convergence problems of Schroedinger equations | Betsy |
Thursday, October 26, 4:30 p.m. in B139 | Fedor Nazarov | Kent State University | The Lerner-Ombrosi-Perez bound in the Muckenhoupt Wheeden conjecture is sharp | Sergey, Andreas |
Friday, October 27, 4:00 p.m. in B239 | Stefanie Petermichl | University of Toulouse | Higher order Journé commutators | Betsy, Andreas |
Wednesday, November 1, 4:00 p.m. in B239 | Shaoming Guo | Indiana University | Parsell-Vinogradov systems in higher dimensions | Andreas |
November 14 | Naser Talebizadeh Sardari | UW Madison | Quadratic forms and the semiclassical eigenfunction hypothesis | Betsy |
November 28 | Xianghong Chen | UW Milwaukee | Title | Betsy |
December 5 | Bartosz Langowski and Tomasz Szarek | Institute of Mathematics, Polish Academy of Sciences | Title | Betsy |
December 12 | Alex Stokolos | GA Southern | Title | Andreas |
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February 6 | Dong Dong | UIUC | Hibert transforms in a 3 by 3 matrix and applications in number theory | Betsy |
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March 13 | Title | |||
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May 1 | Title |
Abstracts
Brian Street
Title: Convenient Coordinates
Abstract: We discuss the method of picking a convenient coordinate system adapted to vector fields. Let X_1,...,X_q be either real or complex C^1 vector fields. We discuss the question of when there is a coordinate system in which the vector fields are smoother (e.g., C^m, or C^\infty, or real analytic). By answering this in a quantitative way, we obtain coordinate charts which can be used as generalized scaling maps. When the vector fields are real this is joint work with Stovall, and continues in the line of quantitative sub-Riemannian geometry initiated by Nagel, Stein, and Wainger. When the vector fields are complex one obtains a geometry with more structure which can be thought of as "sub-Hermitian".
Hiroyoshi Mitake
Title: Derivation of multi-layered interface system and its application
Abstract: In this talk, I will propose a multi-layered interface system which can be formally derived by the singular limit of the weakly coupled system of the Allen-Cahn equation. By using the level set approach, this system can be written as a quasi-monotone degenerate parabolic system. We give results of the well-posedness of viscosity solutions, and study the singularity of each layers. This is a joint work with H. Ninomiya, K. Todoroki.
Joris Roos
Title: A polynomial Roth theorem on the real line
Abstract: For a polynomial P of degree greater than one, we show the existence of patterns of the form (x,x+t,x+P(t)) with a gap estimate on t in positive density subsets of the reals. This is an extension of an earlier result of Bourgain. Our proof is a combination of Bourgain’s approach and more recent methods that were originally developed for the study of the bilinear Hilbert transform along curves. This talk is based on a joint work with Polona Durcik and Shaoming Guo.
Michael Greenblatt
Title: Maximal averages and Radon transforms for two-dimensional hypersurfaces
Abstract: A general local result concerning L^p boundedness of maximal averages over 2D hypersurfaces is described, where p > 2. The surfaces are allowed to have either the traditional smooth density function or a singularity growing as |(x,y)|^{-t} for some 0 < t < 2. This result is a generalization of a theorem of Ikromov, Kempe, and Mueller. Similar methods can be used to show sharp L^p to L^p_a Sobolev estimates for associated Radon transform operators when p is in a certain interval containing 2.
David Beltran
Title: Fefferman Stein Inequalities
Abstract: Given an operator T, we focus on obtaining two-weighted inequalities in which the weights are related via certain maximal function. These inequalites, which originated in work of Fefferman and Stein, have been established in an optimal way for different classical operators in Harmonic Analysis. In this talk, we survey some classical results and we present some recent Fefferman-Stein inequalities for pseudodifferential operators and for the solution operators to dispersive equations.
Jonathan Hickman
Title: Factorising X^n.
Question: how many ways can the polynomial $X^n$ be factorised as a product of linear factors? Answer: it depends on the ring... In this talk I will describe joint work with Jim Wright investigating certain exponential sum estimates over rings of integers modulo N. This theory serves as a discrete analogue of the (euclidean) Fourier restriction problem, a central question in contemporary harmonic analysis. In particular, as part of this study, the question of counting the number of factorisations of polynomials over such rings naturally arises. I will describe how these number-theoretic considerations can themselves be approached via methods from harmonic analysis.
Xiaochun Li
Title: Recent progress on the pointwise convergence problems of Schrodinger equations
Abstract: Recently, Guth, Du and I solved the pointwise convergence problem of Schrodinger equations in two-dimensional case. We proved that the solution to free Schrodinger equation in R^2 converges to its initial data, provided the initial data belongs to H^s for s larger than 1/3. This result is sharp, up to the end point, due to Bourgain's example. The proof relies on the polynomial partitioning method and the decoupling method. In addition, the pointwise convergence problem is closely related to Fourier restriction conjecture.
Fedor Nazarov
Title: The Lerner-Ombrosi-Perez bound in the Muckenhoupt-Wheeden conjecture is sharp.
Abstract: We show that the upper bound $[w]_{A_1}\log (e+[w]_{A_1})$ for the norm of the Hilbert transform on the line as an operator from $L^1(w)$ to $L^{1,\infty}(w)$ cannot be improved in general. This is a joint work with Andrei Lerner and Sheldy Ombrosi.
Stefanie Petermichl
Title: Higher order Journé commutators
Abstract: We consider questions that stem from operator theory via Hankel and Toeplitz forms and target (weak) factorisation of Hardy spaces. In more basic terms, let us consider a function on the unit circle in its Fourier representation. Let P_+ denote the projection onto non-negative and P_- onto negative frequencies. Let b denote multiplication by the symbol function b. It is a classical theorem by Nehari that the composed operator P_+ b P_- is bounded on L^2 if and only if b is in an appropriate space of functions of bounded mean oscillation. The necessity makes use of a classical factorisation theorem of complex function theory on the disk. This type of question can be reformulated in terms of commutators [b,H]=bH-Hb with the Hilbert transform H=P_+ - P_- . Whenever factorisation is absent, such as in the real variable setting, in the multi-parameter setting or other, these classifications can be very difficult.
Such lines were begun by Coifman, Rochberg, Weiss (real variables) and by Cotlar, Ferguson, Sadosky (multi-parameter) of characterisation of spaces of bounded mean oscillation via L^p boundedness of commutators. We present here an endpoint to this theory, bringing all such characterisation results under one roof.
The tools used go deep into modern advances in dyadic harmonic analysis, while preserving the Ansatz from classical operator theory.
Shaoming Guo
Title: Parsell-Vinogradov systems in higher dimensions
Abstract: I will present a few results on counting the numbers of integer solutions of Parsell-Vinogradov systems in higher dimensions. Applications to Waring’s problem and to the problem of counting rational linear subspaces lying on certain hyper-surface will be discussed. Joint works with Jean Bourgain, Ciprian Demeter and Ruixiang Zhang.
Naser Talebizadeh Sardari
Title: Quadratic forms and the semiclassical eigenfunction hypothesis
Abstract: Let be any integral primitive positive definite quadratic form in variables, where , and discriminant . For any integer , we give an upper bound on the number of integral solutions of in terms of , , and . As a corollary, we prove a conjecture of Lester and Rudnick on the small scale equidistribution of almost all functions belonging to any orthonormal basis of a given eigenspace of the Laplacian on the flat torus for . This conjecture is motivated by the work of Berry\cite{Berry, Michael} on semiclassical eigenfunction hypothesis.
Dong Dong
Title: Hibert transforms in a 3 by 3 matrix and applications in number theory
Abstract: This talk could interest both analysts and number theorists. I will first present 35 variants of Hilbert transforms, with a focus on their connections with ergodic theory, number theory, and combinatorics. Then I will show how to use Fourier analysis tools to reduce a number theory problem (Roth theorem) to an algebraic geometry problem: this joint work Li and Sawin fully answers a question of Bourgain and Chang about three-term polynomial progressions in subsets of finite fields. I guarantee that a second-year graduate student can understand at least 50% of the talk.