## Seminar Categories

- Climate Seminar (244)
- Colloquium (21)
- Combinatorics Seminar (1)
- Dynamical Systems (1)
- IMA Data Science Lab Seminar (12)
- IMA/MCIM Industrial Problems Seminar (4)
- MCFAM Distinguished Lecture Series (1)
- MCFAM Seminar (7)
- PDE Seminar (4)
- Probability Seminar (2)
- Special Events and Seminars (11)

## Current Series

Thu Sep 10 |
## Colloquium3:30pm - Zoom ID 91514486597 (contact faculty for pw)Kinetic theory of structured populations: demographics, cell size control, and stochastic hierarchies Tom Chou, University of California, Los Angeles We will briefly review, through two examples, classic deterministic PDE models of population dynamics structured according to attributes such as age and/or size. First, we describe how the original McKendrick model was used to motivate China's one-child policy, and generalize it to include an imposed, finite interbirth refractory period. We quantify the effectiveness of this softer, staggered birth policy and discuss its predicted effectiveness. We then review sizer-timer-adder-type models used to quantify proliferating cell populations. Here, blow-up in mean cell sizes can arise, which represents a challenging numerical problem. Finally, we extend these classic deterministic models to allow for both demographic and growth-rate stochasticity by developing a fully kinetic theory. Marginalization of the full density functions results in a set of coupled kinetic models similar to the BBGKY hierarchy. We map out the different combinations of stochastic descriptions and show how the classic age-dependent population models are connected to this hierarchy, the lowest order of which is a master equation for the total stochastic population. Differences in the stochastic description of birth through budding or splitting are explored. |

Thu Sep 17 |
## Colloquium3:30pm - Zoom ID 91514486597 (contact faculty for pw)25 years since Fermat's Last Theorem Frank Calegari, University of Chicago Wiles's proof of Fermat's Last Theorem was published 25 years ago. Wiles's paper introduced many new ideas and methods which have since shaped the field of algebraic number theory. This colloquium talk intends to give a (biased) tour of these developments, especially with regard to questions that might be of interest to non-specialists. |

Thu Sep 24 |
## Colloquium3:30pm - Zoom ID 91514486597 (contact faculty for pw)Random walks in graph-based learning Jeff Calder, University of Minnesota, Twin Cities I will discuss several applications of random walks to graph-based learning, both for theoretical analysis and algorithm development. Graph-based learning is a field within machine learning that uses similarities between datapoints to create efficient representations of high-dimensional data for tasks like semi-supervised classification, clustering and dimension reduction. Our first application will be to use the random walk interpretation of the graph Laplacian to characterize the lowest label rate at which Laplacian regularized semi-supervised learning is well-posed. Second, we will show how analysis via random walks leads to a new algorithm that we call Poisson learning for semi-supervised learning at very low label rates. Finally, we will show how stochastic coupling of random walks can be used to prove Lipschitz estimates for graph Laplacian eigenfunctions on random geometric graphs, leading to new spectral convergence results. This talk will cover joint work with many people, including Brendan Cook (UMN), Nicolas-Garcia Trillos (Wisconsin-Madison), Marta Lewicka (Pittsburgh), Dejan Slepcev (CMU), Matthew Thorpe (University Manchester). |

Thu Oct 01 |
## Colloquium3:30pm - Zoom ID 91514486597 (contact faculty for pw)Gradient variational problems Richard Kenyon, Yale University This is joint work with Istvan Prause. Many well-known random tiling models such as domino tilings and square ice lead to variational problems for functions h:R^2->R which minimize a functional depending only on the gradient of h. Other examples of such variational problems include minimal surfaces and surfaces satisfying the "p-laplacian". We give a representation of solutions of such a problem in terms of kappa-harmonic functions: functions which are harmonic for a laplacian with a varying conductance kappa. |

Thu Oct 08 |
## Colloquium3:30pm - Zoom ID 91514486597 (contact faculty for pw)Mean-field disordered systems and Hamilton-Jacobi equations Jean-Christophe Mourrat, Courant Institute of Mathematical Sciences, New York University The goal of statistical mechanics is to describe the large-scale behavior of collections of simple elements, often called spins, that interact through locally simple rules and are influenced by some amount of noise. A celebrated model in this class is the Ising model, where spins can take the values +1 and -1, and the local interaction favors the alignement of the spins. In this talk, I will mostly focus on the situation where the interactions are themselves disordered, with some pairs having a preference for alignement, and some for anti-alignement. These models, often called "spin glasses", are already surprisingly difficult to analyze when all spins directly interact with each other. I will describe a fundamental result of the theory called the Parisi formula. I will then explain how this result can be recast using suitable Hamilton-Jacobi equations, and what benefits this new point of view may bring to the topic. |

Thu Oct 15 |
## Colloquium3:30pm - Via ZoomColloquium Daniel Ruberman, Brandeis University |

Thu Oct 22 |
## Colloquium3:30pm - Via ZoomColloquium Edward Frenkel, University of California, Berkeley |

Thu Oct 29 |
## Colloquium3:30pm - Via ZoomColloquium Zhiwei Yun, Massachusetts Institute of Technology |

Thu Nov 05 |
## Colloquium3:30pm - Via ZoomColloquium David Gamarnik, Massachusetts Institute of Technology |

Thu Nov 12 |
## Colloquium3:30pm - Via ZoomColloquium Alexander Kiselev, Duke University |

Thu Nov 19 |
## Colloquium10:00am - Via ZoomColloquium Ana Caraiani, Imperial College London |

Tue Dec 01 |
## Colloquium3:30pm - Via Zoom - Time TBAColloquium Akshay Venkatesh, Institute for Advanced Study |

Thu Dec 03 |
## Colloquium3:30pm - Via ZoomColloquium Vlad Vicol, Courant Institute of Mathematical Sciences, New York University |

Thu Dec 10 |
## Colloquium3:30pm - Via ZoomColloquium Inna Zakharevich, Cornell University |

Thu Jan 28 |
## Colloquium3:30pm - Via ZoomColloquium Wieslawa Niziol, Sorbonne Universite' |

Thu Feb 04 |
## Colloquium3:30pm - Via ZoomColloquium Matthew Baker, Georgia Institute of Technology |

Thu Feb 11 |
## Colloquium3:30pm - Via ZoomColloquium Sijue Wu, University of Michigan, Ann Arbor |

Thu Feb 18 |
## Colloquium5:00pm - Via ZoomColloquium Takeshi Saito, University of Tokyo |

Thu Feb 25 |
## Colloquium3:30pm - Via ZoomColloquium Thomas Lam, University of Michigan, Ann Arbor |

Thu Mar 04 |
## Colloquium3:30pm - Via ZoomColloquium Xinwen Zhu, California Institute of Technology |

Thu Mar 25 |
## Colloquium10:00am - Via Zoom (note special time)Colloquium Carola-Bibiane Schönlieb, Cambridge University |

Thu Apr 01 |
## Colloquium3:30pm - Via ZoomColloquium David Ben-Zvi, University of Texas, Austin |

Thu Apr 08 |
## Colloquium3:30pm - Via ZoomColloquium Kavita Ramanan, Brown University |

Thu Apr 29 |
## Colloquium3:30pm - Via ZoomColloquium Tatiana Toro, University of Washington |