CMSA

5/4/2020 Condensed Matter Seminar
2020-05-04 10:30 - 12:30 (America/New_York)

5/4/2020 Mathematical Physics Seminar
2020-05-04 10:30 - 12:00

4/30/2020 Condensed Matter Seminar
2020-04-30 10:30 - 12:00

4/29/2020 Random Matrix and Probability Theory Seminar
2020-04-29 14:00 - 15:00

4/29/2020 Quantum Matter Seminar
2020-04-29 10:30 - 12:00

4/27/2020 Math-Physics Seminar
2020-04-27 00:00 - 13:00

4/23/2020 Condensed Matter Seminar
2020-04-23 10:30 - 12:00

4/22/2020 RM&PT Seminar
2020-04-22 14:00 - 15:00 | Virtual

4/22/2020 Quantum Matter Seminar
2020-04-22 10:30 - 12:00

4/20/2020 Math Physics Seminar
2020-04-20 00:00 - 13:00

4/16/2020 Condensed Matter Seminar
2020-04-16 10:30 - 12:00 | Virtual

Stability of spacetimes with supersymmetric compactifications
2020-04-15 16:30 - 17:30 | Virtual
Speaker: Lars Andersson (Max-Planck Institute for Gravitational Physics)
Title: Stability of spacetimes with supersymmetric compactifications
Abstract: Spacetimes with compact directions, which have special holonomy such as Calabi-Yau spaces, play an important role in supergravity and string theory. In this talk I will discuss the global, non-linear stability for the vacuum Einstein equations on a spacetime which is a cartesian product of a high dimensional Minkowski space with a compact Ricci flat internal space with special holonomy. I will start by giving a brief overview of related stability problems which have received a lot of attention recently, including the black hole stability problem. This is based on joint work with Pieter Blue, Zoe Wyatt, and Shing-Tung Yau.

CMSA Math-Science Literature Lecture: Why do some universities have separate departments of statistics?
2020-04-15 08:00 - 09:00 | Virtual
Donald Rubin (Harvard)
Title: Why do some universities have separate departments of statistics? And are they all anachronisms, destined to follow the path of other dinosaurs?
Video | Slides

4/13/2020 Math-Physics Seminar
2020-04-13 12:00 - 2020-04-22 13:00

4/8/2020 Quantum Matter seminar
2020-04-08 10:30 - 12:00

CMSA Math-Science Literature Lecture: The ADHM construction of Yang-Mills instantons
2020-04-04 15:00 - 16:00 | Virtual
Simon Donaldson (Stony Brook)
Title: The ADHM construction of Yang-Mills instantons
Abstract: In 1978 (Physics Letters 65A) Atiyah, Hitchin, Drinfeld and Manin (ADHM) described a construction of the general solution of the Yang-Mills instanton equations over the 4-sphere using linear algebra. This was a major landmark in the modern interaction between geometry and physics, and the construction has been the scene for much research activity up to the present day. In this lecture we will review the background and the original ADHM proof, using Penrose’s twistor theory and results on algebraic vector bundles over projective 3-space. As time permits, we will also discuss some further developments, for example, the work of Nahm on monopoles and connections to Mukai duality for bundles over complex tori.
Video | Slides

4/3/2020 General Relativity Seminar
2020-04-03 10:30 - 12:00 | Virtual

4/1/2020 Random Matrix and Probability Theory Seminar
2020-04-01 14:00 - 15:00

3/30/2020 Math Physics Seminar
2020-03-30 11:00 - 12:00

3/27/2020 General Relativity Seminar
2020-03-27 10:30 - 11:30

3/25/2020 Quantum Matter seminar
2020-03-25 10:30 - 12:00

Frontiers in Applied Mathematics and Computation
2020-03-25 10:00 - 2020-04-29 14:00 | Virtual
Together with the School of Engineering and Applied Sciences, the CMSA will be hosting a lecture series on the Frontiers in Applied Mathematics and Computation. Talks in this series will aim to highlight current research trends at the interface of applied math and computation and will explore the application of these trends to challenging scientific, engineering, and societal problems.
Lectures will take place on March 25, April 1, and April 29, 2021.
Speakers:

George Biros (U.T. Austin)
Laura Grigori (INRIA Paris)
Samory K. Kpotufe (Columbia)
Jonas Martin Peters (University of Copenhagen)
Joseph M. Teran (UCLA)

The schedule below will be updated as talks are confirmed.

Date/Time
Speaker
Title/Abstract

3/25/2021
10:00 – 11:00am ET
Joseph M. Teran
Title: Affine-Particle-In-Cell with Conservative Resampling and Implicit Time Stepping for Surface Tension Forces
Abstract: The Particle-In-Cell (PIC) method of Harlow is one of the first and most widely used numerical methods for Partial Differential Equations (PDE) in computational physics. Its relative efficiency, versatility and intuitive implementation have made it particularly popular in computational incompressible flow, plasma physics and large strain elastoplasticity. PIC is characterized by its dual particle/grid (Lagrangian/Eulerian) representation of material where particles are generally used to track material transport in a Lagrangian way and a structured Eulerian grid is used to discretize remaining spatial derivatives in the PDE. I will discuss the importance of conserving linear and angular momentum when switching between these two representations and the recent Affine-Particle-In-Cell (APIC) extension to PIC designed for this conservation. I will also discuss a recent APIC technique for discretizing surface tension forces and their linearizations needed for implicit time stepping. This technique is characterized by a novel surface resampling strategy and I will discuss a generalization of the APIC conservation to this setting.

4/1/2021
9:00 – 10:00am ET
George Biros
Title: Inverse biophysical modeling and its application to neurooncology
Abstract: A predictive, patient-specific, biophysical model of tumor growth would be an invaluable tool for causally connecting diagnostics with predictive medicine. For example, it could be used for tumor grading, characterization of the tumor microenvironment, recurrence prediction, and treatment planning, e.g., chemotherapy protocol or enrollment eligibility for clinical trials. Such a model also would provide an important bridge between molecular drivers of tumor growth and imaging-based phenotypic signatures, and thus, help identify and quantify mechanism-based associations between these two. Unfortunately, such a predictive biophysical model does not exist. Existing models undergoing clinical evaluation are too simple–they do not even capture the MRI phenotype. Although many highly complex models have been proposed, the major hurdle in deploying them clinically is their calibration and validation.
In this talk, I will discuss the challenges related to the calibration and validation of biophysical models, and in particular the mathematical structure of the underlying inverse problems. I will also present a new algorithm that localizes the tumor origin within a few millimeters.

4/1/2021
10:00 – 11:00am ET
Samory K. Kpotufe
Title: From Theory to Clustering
Abstract: Clustering is a basic problem in data analysis, consisting of partitioning data into meaningful groups called clusters. Practical clustering procedures tend to meet two criteria: flexibility in the shapes and number of clusters estimated, and efficient processing. While many practical procedures might meet either of these criteria in different applications, general guarantees often only hold for theoretical procedures that are hard if not impossible to implement. A main aim is to address this gap.
We will discuss two recent approaches that compete with state-of-the-art procedures, while at the same time relying on rigorous analysis of clustering. The first approach fits within the framework of density-based clustering, a family of flexible clustering approaches. It builds primarily on theoretical insights on nearest-neighbor graphs, a geometric data structure shown to encode local information on the data density. The second approach speeds up kernel k-means, a popular Hilbert space embedding and clustering method. This more efficient approach relies on a new interpretation – and alternative use – of kernel-sketching as a geometry-preserving random projection in Hilbert space.
Finally, we will present recent experimental results combining the benefits of both approaches in the IoT application domain.
The talk is based on various works with collaborators Sanjoy Dasgupta, Kamalika Chaudhuri, Ulrike von Luxburg, Heinrich Jiang, Bharath Sriperumbudur, Kun Yang, and Nick Feamster.

4/29/2021
12:00 – 1:00pm ET
Jonas Martin Peters
Title: Causality and Distribution Generalization
Abstract: Purely predictive methods do not perform well when the test distribution changes too much from the training distribution. Causal models are known to be stable with respect to distributional shifts such as arbitrarily strong interventions on the covariates, but do not perform well when the test distribution differs only mildly from the training distribution. We discuss anchor regression, a framework that provides a trade-off between causal and predictive models. The method poses different (convex and non-convex) optimization problems and relates to methods that are tailored for instrumental variable settings. We show how similar principles can be used for inferring metabolic networks. If time allows, we discuss extensions to nonlinear models and theoretical limitations of such methodology.

4/29/2021
1:00 – 2:00pm ET
Laura Grigori
Title: Randomization and communication avoiding techniques for large scale linear algebra
Abstract: In this talk we will discuss recent developments of randomization and communication avoiding techniques for solving large scale linear algebra operations. We will focus in particular on solving linear systems of equations and we will discuss a randomized process for orthogonalizing a set of vectors and its usage in GMRES, while also exploiting mixed precision. We will also discuss a robust multilevel preconditioner that allows to further accelerate solving large scale linear systems on parallel computers.

3/23/2020 Math Physics Seminar
2020-03-23 12:00 - 13:00

CMSA Math-Science Literature Lecture: Shiing-Shen Chern as a Great Geometer of 20th Century
2020-03-13 14:00 - 15:00 | Virtual
Shing-Tung Yau (Harvard)
Title: Shiing-Shen Chern as a Great Geometer of 20th Century
Video | Slides | Article

Math, Music and the Mind; Mathematical analysis of the performed Trio Sonatas of J. S. Bach
2020-03-12 16:00 - 17:00 | CMSA, 20 Garden Street, Cambridge, MA, 02138, United States
Speaker: Daniel Forger (UMich)

Location: CMSA building, 20 Garden Street, Room G10

Title: Math, Music and the Mind; Mathematical analysis of the performed Trio Sonatas of J. S. Bach

Abstract: I will describe a collaborative project with the University of Michigan Organ Department to perfectly digitize many performances of difficult organ works (the Trio Sonatas by J.S. Bach) by students and faculty at many skill levels. We use these digitizations, and direct representations of the score to ask how music should encoded in the mind. Our results challenge the modern mathematical theory of music encoding, e.g., based on orbifolds, and reveal surprising new mathematical patterns in Bach’s music. We also discover ways in which biophysical limits of neuronal computation may limit performance.

3/11/2020 Quantum Matter Seminar
2020-03-11 10:30 - 12:00

3/10/2020 Special Seminar
2020-03-10 10:30 - 11:30

3/9/2020 Mathematical Physics Seminar
2020-03-09 12:00 - 13:00

3/9/2020 Special Seminar
2020-03-09 10:30 - 11:00

3/06/2020 General Relativity Seminar
2020-03-06 10:30 - 11:30
