## Math Calendar

Tuesday, September 25, 2018

16:00-17:00

HFG 611

Utrecht Geometry Center Seminar

Cary Malkiewich (SUNY Binghamton/MPIM Bonn) - The transfer map of free loop spaces

see description

Let R -> A be a map of rings (or ring spectra) and suppose that A is finitely generated projective (or perfect) as an R-module. Then there is a wrong-way "transfer" map on algebraic K-theory, K(A) -> K(R). In particular, when E -> B is a fibration whose fiber F is a finite CW complex, this gives a wrong-way map on Waldhausen's functor A(B) -> A(E). We ask a few fundamental questions about this transfer, and present the beginning of a program to answer these questions using trace methods. Our main result concerns the corresponding transfer in topological Hochschild homology (THH), which is a stable map of free loop spaces LB -> LE. Aside from the insights into algebraic K-theory, these results appear to give us new computational tools for the homology of free loop spaces. This is joint work with John Lind.

Wednesday, September 26, 2018

11:00-12:00

BBG 7.12

Mathematical Physics Seminar

Martijn Kool (UU) - New calculations in Vafa-Witten theory

see description

Abstract: "In the 1990's, Vafa-Witten tested S-duality of N=4 SUSY Yang-Mills theory on a complex algebraic surface by studying modularity of a certain partition function. Recently, a mathematical definition of Vafa-Witten's invariants was given by Tanaka-Thomas. I outline a method for calculating the instanton contribution to these invariants using Mochizuki's theory of algebraic Donaldson invariants. For SU(2), this leads to verifications of Vafa-Witten's original formula. For SU(3), we find a surprising new formula which corrects an error in the physics literature. I discuss refinements of our instanton calculations to virtual \chi_y genus, elliptic genus, and cobordism class, which involves Jacobi forms and Borcherds lifts thereof. Joint with Göttsche."

Tuesday, October 2, 2018

16:00-17:00

Thursday, October 4, 2018

16:00-17:00

Utrecht

Tuesday, October 9, 2018

16:00-17:00

Thursday, October 11, 2018

16:00-17:00

Utrecht

Tuesday, October 16, 2018

Tuesday, October 23, 2018

16:00-17:00

Utrecht Geometry Center Seminar

Cristina Manolache (Imperial College London) - A splitting of the virtual class for genus one stable maps, HFG 611

see description

In order to define intersection theory on spaces with several components of different dimensions one needs to define a "virtual class". I will explain the construction of the virtual class in simple examples and then show how to split this class on components. I will discuss applications to moduli spaces of genus one stable maps.

Thursday, October 25, 2018

16:00-17:00

Utrecht

Tuesday, October 30, 2018

16:00-17:00

Utrecht Geometry Center Seminar

Emmanuel Kowalski (ETH Zürich) - Stories of Kloosterman sums, HFG 611

see description

Kloosterman sums are finite exponential sums which have remarkable

applications in analytic number theory, ranging from diophantine

problems to modular forms and the distribution of primes.

The talk will present the history of the study of these sums and

discuss their properties, including a number of open problems. There

will be a particular emphasis on links with algebraic geometry, and on

distribution problems for Kloosterman sums.

applications in analytic number theory, ranging from diophantine

problems to modular forms and the distribution of primes.

The talk will present the history of the study of these sums and

discuss their properties, including a number of open problems. There

will be a particular emphasis on links with algebraic geometry, and on

distribution problems for Kloosterman sums.

Tuesday, November 6, 2018

16:00-17:00

Thursday, November 8, 2018

16:00-17:00

Utrecht

Tuesday, November 13, 2018

16:00-17:00

Utrecht Geometry Center Seminar

Jonathan Belletête (CEA Saclay) - A pseudo-fusion category from Temperley-Lieb algebras, HFG 611

see description

Two dimensional conformal field theories, appearing in many branches of physics, can be ( partially ) encoded into a category of representations of some vertex operator algebra; there the tensor product of representations encodes the interactions of the particles in the theory. If these interactions are sufficiently well-behaved, then this will be a Fusion category; these appear in many areas of mathematics, for instance in the representation theory of Hopf algebras, in the construction of 3D topological invariants, etc. The question is then: what if the interactions are not well-behaved? One can show easily that the defining axioms of a Fusion category are then no longer satisfied, but how should they be replaced?

The Temperley-Lieb algebras are an infinite family of associative algebras indexed by two parameters: a positive integer N and a complex number q. Physicists have argued that these algebras can be used to build 2d conformal field theories, in particular ones where the interactions are well-behaved, and ones where they are not. I will show how their categories of representations can be turned into proper tensor categories; I will discuss how these can be understood as Fusion categories in certain cases, and what happens when they can't.

Based on joint work with Yvan Saint-Aubin.

The Temperley-Lieb algebras are an infinite family of associative algebras indexed by two parameters: a positive integer N and a complex number q. Physicists have argued that these algebras can be used to build 2d conformal field theories, in particular ones where the interactions are well-behaved, and ones where they are not. I will show how their categories of representations can be turned into proper tensor categories; I will discuss how these can be understood as Fusion categories in certain cases, and what happens when they can't.

Based on joint work with Yvan Saint-Aubin.

Thursday, November 15, 2018

16:00-17:00

Utrecht

Tuesday, November 20, 2018

16:00-17:00

Thursday, November 22, 2018

16:00-17:00

Utrecht

Tuesday, November 27, 2018

16:00-17:00

Thursday, November 29, 2018

Tuesday, December 4, 2018

16:00-17:00

Thursday, December 6, 2018

16:00-17:00

Utrecht

Tuesday, December 11, 2018

16:00-17:00

Thursday, December 13, 2018

Tuesday, December 18, 2018

16:00-17:00

Tuesday, January 8, 2019

Tuesday, January 15, 2019

Tuesday, January 22, 2019

Tuesday, January 29, 2019

16:00-17:00

Thursday, January 31, 2019

16:00-17:00

Utrecht

Tuesday, February 5, 2019

Thursday, February 7, 2019

Thursday, February 14, 2019

16:00-17:00

Utrecht

Thursday, March 7, 2019

16:00-17:00

Utrecht

Thursday, March 14, 2019

16:00-17:00

Utrecht

Thursday, March 21, 2019