COMPUTATIONAL MATH – IDeAS SEMINAR Recurring weekly series · Thursdays, 2:00 – 3:00 PM · Jadwin 111 This week's talk: Speaker: Ethan Nicholas Epperly (UC Berkeley) Title: Sparser, better, faster, stronger: Emerging approaches in the theory and practice of randomized dimensionality reduction. Date: Thursday, February 26, 2026 Time: 2:00 PM – 3:00 PM Room: Jadwin 111 Abstract: For approaching thirty years, randomized dimensionality reduction techniques have been a core tool in the theory and practice of computation. But despite this robust history, basic questions remain hotly debated: Which dimensionality reduction map should be used? How can the map be adapted to structure in the problem? What is the right theoretical approach to analyzing randomized dimensionality reduction? This talk presents a new approach to the theory of randomized dimensionality reduction under which the core feature of a good dimensionality map is injectivity: It is fine if the map stretches things out a bit as long as it does not annihilate any element of the data space. This new approach yields new analysis of sparse and tensor-structured dimensionality reduction maps that comes closer to describing how these maps behave in practice. This talk is designed for a general audience and assumes no prior familiarity with randomized dimensionality reduction. About the speaker: Ethan is a Miller Research Fellow in the Mathematics Department at UC Berkeley. His research is focused on designing computational techniques for solving large-scale computational problems in machine learning, quantum information, and scientific computing, with a focus on randomized algorithms. He received his PhD in Applied and Computational Mathematics from Caltech. He has been recognized for his work with finalist status for the Hertz Foundation Fellowship, Caltech's Thomas A. Tisch Prize for Graduate Teaching in CMS and W. P. Carey & Co. Prize in Applied Mathematics, and the SIAM Student Paper Prize. His PhD research was supported by a Department of Energy Computational Science Graduate Fellowship. Up next: Thursday, March 5 – Per-Gunnar Martinsson (The University of Texas). Same time, same place. The IDeAS Seminar series is hosted by Liza Rebrova (ORFE), Marc Aurèle Gilles and Jorge Garza Vargas (MATH).