Speaker: Miles Couchman (York University)Title: Turbulent mixing in stratified flowsAbstract:Understanding how turbulence enhances the irreversible mixing of scalars in density-stratified fluids is a central problem in industrial and geophysical fluid dynamics. For instance, accurately parametrizing turbulent heat transport within the ocean is a leading area of uncertainty in climate modelling. We here present a series of data-driven approaches for quantifying the spatiotemporal distribution of mixing hotspots and structures in turbulence datasets.First, we describe an unsupervised clustering technique for analyzing oceanographic data, highlighting that traditional analyses may significantly underestimate mixing generated by rare, extreme events. We then consider mixing in complementary direct numerical simulations, revealing the importance of stable anisotropic density interfaces embedded within the flow. Finally, we introduce a dimensionality-reduction algorithm for classifying experimental videos of stratified flow instabilities, leading to a cluster-based network model quantifying turbulent transition pathways.Collectively, our findings highlight that extreme mixing events have the potential to dominate bulk mixing statistics. Current parametrizations of turbulent heat transport may thus be skewed by undersampled measurements, resulting in a focus on the most common, but not necessarily the most significant, events.

Ten minutes for your mind@2:50 every day at 2:50 pm in multiple time zones:Europa@2:50, EET, Athens, Helsinki (UTC+2) (7:50 am EST) https://us02web.zoom.us/j/88298032734Atlantica@2:50, EST, New York, Toronto (UTC-4) https://us02web.zoom.us/j/85349851047Pacifica@2:50, PST, Los Angeles, Vancouver (UTC=7) (5:50 pm EST) https://us02web.zoom.us/j/85743543699Almost everything works better again if you unplug it for a bit, including your mind. Stop by and unplug. Get the benefits of mindfulness without the fuss.@2:50 meets at the same time every single day for ten minutes of quiet together.No pre-requisite, no registration needed.Visit the website to view all @2:50 time zones each day.at250.org or at250.mit.edu

Speakers: Xuerui Yang (University of Illinois, Urbana-Champaign)Title: On the Gauss Circle ProblemAbstract: The circle problem has been a notorious problem in number theory. It boils down to derive an effective bound on certain two-dimensional exponential sum over the integer ring. I will talk about how to connect this pointwise bound problem to a mean-value-estimate problem. Then, I will explain how decoupling theory can help us solve the mean value problem.

The Department of Mathematics welcomes École Polytechnique Fédérale de Lausanne professor Maryna Viazovska to our annual Simons Lecture Series.She will give three lectures April 29-May 1The Sphere Packing Problem Lecture 1: General overview. Lecture 2: Random sphere packings with symmetries Lecture 3: Ideal lattice packings and subconvexity bounds IIEach day, a reception will be held at 4pm in Room 2-290, followed by the 4:30pm lecture in Room 2-190.This annual lecture series features presentations by top mathematicians. Many thanks to the late Jim Simons and his wife, Marilyn Simons, for their continued financial support of these lectures.

Abstract: The intensifying development of machine learning (ML) models and the adoption of artificial intelligence (AI) tools, particularly generative AI, has dramatically shifted practices around data, spurring the development of new industries and unveiling unprecedented forms of exploitation. These new complexities around the production, refinement, and use of data indicate severe implications for African countries, including the widescale spread of generative AI-driven disinformation, increased manipulation exacerbated by digital platforms, and the continuation of colonial-era marginalization through datafication practices. These concerns elevate a need for comprehensive and harmonized data regulation efforts across the African continent, given existing challenges with fragmented policy implementation and limited capacity for regulatory enforcement. This talk examines the burgeoning AI and data governance landscape in Africa, analyzing the impact of AI on democratic processes, outlining best measures for data governance policy reform, and delineating priorities to democratize African participation in global AI governance.Bio: Chinasa T. Okolo, Ph.D., is a Fellow at The Brookings Institution and a recent Computer Science Ph.D. graduate from Cornell University. Her research focuses on AI governance for the Global Majority, datafication and algorithmic marginalization, and the socioeconomic impact of data work. Dr. Okolo has been recognized as one of the world’s most influential people in AI by TIME, honored in the inaugural Forbes 30 Under 30 AI list, and advises numerous multilateral institutions, national governments, corporations, and nonprofits. In addition to her work at Brookings, Dr. Okolo serves as a Drafting Member of the Nigerian National AI Strategy, a Consulting Expert to the African Union AI Continental Strategy, an Expert Contributing Writer to the International AI Safety Report, and the Editor-in-Chief of ACM SIGCAS Computers and Society. Her research has been covered widely in media outlets and published at top-tier venues in human-computer interaction and sociotechnical computing.This event is co-sponsored by the MIT Schwarzman College of Computing and Laboratory for Information and Decision Systems.

Speaker: Rebecca Heald, University of California, BerkeleyHost: Adam MartinTitle: "Mechanisms and consequences of size scaling in frogs"The Biology Colloquium is a weekly seminar held throughout the academic year — featuring distinguished speakers in many areas of the biological sciences from universities and institutions worldwide. More information on speakers, their affiliations, and titles of their talks will be added as available. Unless otherwise stated, the Colloquium will be held live in Stata 32-123 (Kirsch auditorium) Contact Margaret Cabral with questions.