School of Mathematics

Structural aspects of the null-cone problem in invariant theory

Ankit Garg
Microsoft Research
October 10, 2017
Invariant theory studies the actions of groups on vector spaces and what polynomial functions remain invariant under these actions. An important object related to a group action is the null cone, which is the set of common zeroes of all homogeneous invariant polynomials. I will talk about the structural aspects of the null cone from a computational and optimization perspective. These will include the Hilbert-Mumford and Kempf-Ness theorems which imply that null cone membership is in NP intersect coNP (ignoring bit-size issues).

Analysis and topology on locally symmetric spaces

Akshay Venkatesh
Stanford University; Distinguished Visiting Professor, School of Mathematics
October 9, 2017
Locally symmetric spaces are a class of Riemannian manifolds which play a special role in number theory. In this talk, I will introduce these spaces through example, and show some of their unusual properties from the point of view of both analysis and topology. I will conclude by discussing their (still very mysterious) relationship with algebraic geometry.

Barriers for rank methods in arithmetic complexity

Rafael Oliveira
University of Toronto
October 9, 2017

Arithmetic complexity is considered (for many good reasons) simpler to understand than Boolean complexity. And indeed, we seem to have significantly more lower bound techniques and results in arithmetic complexity than in Boolean complexity. Despite many successes and rapid progress, however, foundational challenges, like proving super-polynomial lower bounds on circuit or formula size for explicit polynomials, or super-linear lower bounds on explicit 3-dimensional tensors, remain elusive.

Wrapped Floer theory and Homological mirror symmetry for toric Calabi-Yau manifolds

Yoel Groman
Columbia University
October 9, 2017
Consider a Lagrangian torus fibration a la SYZ over a non compact base. Using techniques from arXiv:1510.04265, I will discuss the construction of wrapped Floer theory in this setting. Note that this setting is generally not exact even near infinity. The construction allows the formulation of a version of the homological mirror symmetry conjecture for open manifolds which are not exact near infinity.