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# Elliptic Cohomology and Physics

Elliptic Cohomology and Physics

## Conformal blocks in genus zero, and Elliptic cohomology

Jeudi mai 28, 2020
Speaker(s):

A fundamental theorem in the theory of Vertex algebras (known as Zhu’s theorem) demonstrates that the space generated by the characters of certain Vertex algebras is a representation of the modular group. We will cast this theorem in the language of homotopy theory using the language of conformal blocks. The goal of this talk is to justify the claim that equivariant elliptic cohomology, seen as a derived spectrum, is a homotopical analog of Zhu’s theorem in the special case of the Affine Vacuum vertex algebra at a fixed integral level.

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## Quasi-elliptic cohomology theory and the twisted, twisted Real theories

Jeudi mai 28, 2020
Speaker(s):

Quasi-elliptic cohomology is closely related to Tate K-theory. It is constructed as an object both reflecting the geometric nature of elliptic curves and more practicable to study than most elliptic cohomology theories. It can be interpreted by orbifold loop spaces and expressed in terms of equivariant K-theories. We formulate the complete power operation of this theory. Applying that we prove the finite subgroups of Tate curve can be classified by the Tate K-theory of symmetric groups modulo a certain transfer ideal.

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## Sigma-VOA correspondence

Jeudi mai 28, 2020
Speaker(s):

In this talk I will discuss an interesting phenomenon, namely a correspondence between sigma models and vertex operator algebras, with the two related by their symmetry properties and by a reflection
procedure, mapping the right-movers of the sigma model at a special
point in the moduli space to left-movers. We will discuss the examples
of N=(4,4) sigma models on $T^4$ and on $K3$. The talk will be based
on joint work with Vassilis Anagiannis, John Duncan and Roberto
Volpato.

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## Elliptic characteristic classes, bow varieties, 3d mirror duality

Mercredi mai 27, 2020
Speaker(s):

We study elliptic characteristic classes of natural subvarieties in some ambient spaces, namely in homogeneous spaces and in Nakajima quiver varieties. The elliptic versions of such characteristic classes display an unexpected symmetry: after switching the equivariant and the Kahler parameters, the classes of varieties in one ambient space coincide” with the classes of varieties in another ambient space. This duality gets explained as “3d mirror duality” if we regard our ambient spaces as special cases of Cherkis bow varieties. I will report on a work in progress with Y.

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## Twisted superconformal algebras and representations of higher Virasoro algebras

Mercredi mai 27, 2020
Speaker(s):

(Super)conformal algebras on two-dimensional spacetimes play a ubiquitous role in representation theory and conformal field theory. In most cases, however, superconformal algebras are finite dimensional. In this talk, we introduce refinements of certain deformations of superconformal algebras which share many facets with the ordinary (super) Virasoro algebras. Representations of these refinements include the higher dimensional Kac—Moody algebras, and many more motivated by physics.

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## Codes, vertex algebras and topological modular forms

Mercredi mai 27, 2020
Speaker(s):

The talk illuminates the role of codes and lattice vertex algebras in algebraic topology. These objects come up naturally in connection with string structures or topological modular forms. The talk tries to unify these different concepts in an introductory manner.

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## Quasisymmetric characteristic numbers for Hamiltonian toric manifolds

Mardi mai 26, 2020
Speaker(s):

Baker and Richter's $A_\infty$ analog of the complex cobordism spectrum provides characteristic numbers for complex-oriented toric manifolds, which generalize to define similar invariants for Hamiltonian toric dynamical systems: roughly, the `completely integrable' systems of classical mechanics which (by KAM theory) possess remarkable stability properties. arXiv:1910.12609

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## The de Rham model for elliptic cohomology from physics

Mardi mai 26, 2020
Speaker(s):

I'll discuss elliptic cohomology from a physical perspective, indicating the importance of the Segal-Stolz-Teichner conjecture and joint work with D. Berwick-Evans on rigorously proving some of these physical predictions.

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## Equivariant elliptic cohomology with integral coefficients

Mardi mai 26, 2020
Speaker(s):

Thirteen years ago, Lurie has sketched a way to obtain equivariant elliptic cohomology and equivariant topological modular forms without the need to restrict to rational or complex coefficients. Recently, David Gepner and I have found one way to flesh out the details and and provide computations in the U(1)-equivariant case. On this work I will report.

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## Topological Modular Forms and Quantum Field Theory

Lundi mai 25, 2020
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## LECTURES ON-DEMAND

### Gabriela González, Louisiana State University

Speaker: Gabriela Gonzalez