Thu, 08 May 2025

12:00 - 13:00
L3

Low-rank methods for discovering structure in data tensors in neuroscience

Alex Cayco-Gajic
(École Normale Supérieure Paris)
Further Information

Short Bio

Alex Cayco Gajic is a Junior Professor in the Department of Cognitive Studies at ENS, with a background in applied mathematics and a PhD from the University of Washington. Her research bridges computational modelling and data analysis to study cerebellar function, exploring its roles beyond motor control in collaboration with experimental neuroscientists.

Abstract

A fundamental question in neuroscience is to understand how information is represented in the activity of  tens of thousands of neurons in the brain. Towards this end, low-rank matrix and tensor decompositions are commonly used to identify correlates of behavior in high-dimensional neural data. In this talk I will first present a novel tensor decomposition based on the slice rank which is able to disentangle mixed modes of covarying patterns in data tensors. Second, to compliment this statistical approach, I will present our recent dynamical systems modelling of neural activity over learning. Rather than factorizing data tensors themselves, we instead fit a dynamical system to the data, while constraining the tensor of parameters to be low rank. Together these projects highlight how applications in neural data can inspire new classes of low-rank models.

Thu, 01 May 2025

12:00 - 13:00
L3

Do Plants Know Math?: Adventures of a Mathematician in Science Writing

Christophe Golé
(Smith College)
Further Information

Short Bio
Christophe Golé is a mathematician originally from France, with academic positions held at institutions including ETH Zurich and UC Santa Cruz. He is the author of Symplectic Twist Maps, a book on dynamical systems, and coined the term “ghost tori” in this context. His recent work focuses on mathematical biology, particularly plant pattern formation (phyllotaxis) and the occurrence of Fibonacci numbers in nature. He co-founded the NSF-funded 4 College Biomath Consortium, which led to the Five College Biomathematical Sciences Certificate Program.

Abstract

"Do Plants Know Math?" is the title of a book I co-authored with physicist Stéphane Douady, biologist Jacques Dumais, and writer Nancy Pick. Written for a general audience with a historical perspective, the book primarily explores phyllotaxis—the arrangement of leaves and other organs around plant stems—while also examining plant fractals, kirigami models of leaf formation, and related phenomena.

To our knowledge, phyllotaxis represents the first historical intersection of biological and mathematical research. Delving into its history uncovers remarkable treasures: phyllotaxis studies led to the first formulation of renormalization (van Iterson, 1907) and inspired one of the earliest computer programs (developed by Turing in the last years of his life).

In this talk, I will highlight several of these hidden historical gems while discussing the productive symbiosis between our scientific research on phyllotaxis and the creation of our book.

----

Reach run Summer Schools in Oxford. You know, the ones where 100s of international kids loll around in the University Parks for hour after hour. On a serious note, they are looking for DPhil-level tutors and pay okay. Below is their blurb: 

Jan in front of a whiteboard

Information Theory, formalised by Claude Shannon in the 1940s, is one of the planks of 20th and 21st century science. You can now watch eight lectures we're showing from Sam Cohen's popular 3rd year Oxford Mathematics course, part of our aim of making more of our teaching visible to a wider audience.

Exact identifiability analysis for a class of partially observed
near-linear stochastic differential equation models
Browning, A Chappell, M Rahkooy, H Loman, T Baker, R (25 Mar 2025) http://arxiv.org/abs/2503.19241v1
Biased estimator channels for classical shadows
Cai, Z Chapman, A Jnane, H Koczor, B Physical Review A volume 111 issue 3 l030402 (21 Mar 2025)
Bordism categories and orientations of moduli spaces
Joyce, D Upmeier, M (26 Mar 2025)
Zero-homogeneous and $O(2)$-equivariant critical points of the
Oseen-Frank energy with multiple Frank constants
Nguyen, L (28 Mar 2025) http://arxiv.org/abs/2503.22599v1
The edges of glaciology
Fowler, A Ng, F Annals of Glaciology volume 66 e11 (26 Mar 2025)
Subscribe to