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Author Archives: Victoria Hain

Albrecht Klemm: Lectures

September 11, 2019
TITLE: CY 3-folds over finite fields, Black hole attractors, and D-brane masses

ABSTRACT: The integer coefficients of the numerator of the Hasse-Weil Zeta function for one parameter Calabi-Yau 3-folds are expected to be Hecke eigenvalues of Siegel modular forms. For rigid CY 3-folds as well as at conifold — and rank two attractor points this numerator contains factors of lower degree, which can be shown to be the Hecke eigenvalues of weight two or four of modular cusp forms of \Gamma_0(N). We show that the Hecke L-function at integer arguments or more generally the periods of these modular forms give the D-brane masses as well as the value and the curvature of the Weil-Peterssen metric at the points. The coefficients of the connection matrix from the integer symplectic basis to a Frobenius basis at the conifold are given by the quasi periods of these modular forms.

Cumrun Vafa: Lectures

September 11, 2019
TITLE: G2 Structure and Physical Interpretation of Taubes Construction of SW Invariants

ABSTRACT:  In this talk I review a joint recent work with Sergio Cecotti, where we use the G_2 structure to shed light on Taubes reformulation of SW invariant for symplectic 4-manifolds in terms of Gromov invariants.

Andrei Moroianu: Lectures

September 10, 2019
TITLE: Toric nearly Kähler 6-manifolds

ABSTRACT: Nearly Kähler manifolds are a particular class of almost Hermitian manifolds in the Gray-Hervella classification, but for several reasons they are mostly relevant in dimension 6, where (normalized, strict) nearly Kähler 6-manifolds can be characterized by the fact that their metric cone has holonomy contained in \mathrm{G}_2. In this talk, based on a joint work with P.-A. Nagy, I will show that strict nearly Kähler 6-manifolds admitting effective \mathbb{T}^3 actions by automorphisms are characterized in the neigbourhood of each point by a function on \mathbb{R}^3 satisfying a certain Monge–Ampère-type equation.

Chris Hull: Lectures

September 10, 2019
TITLE: Special Holonomy Metrics, Degenerate Limits and Intersecting Branes

ABSTRACT: The starting point for this talk is the degenerate limit of K3 constructed by Hein, Sun, Viaclovsky and Zhang, with a long neck that can be thought of as a 3-dimensional nilmanifold fibred over a line, with gravitational instanton insertions. Special holonomy generalisations of this neck region that are given by higher dimensional nilmanifolds fibred over a line will be discussed. They are dual to intersecting brane solutions, and this relation leads to more general solutions. The possibility of these arising as part of a degenerate limit of a compact special holonomy space will be considered, and applications to string theory will be explored.

Slides of lecture

Brian Willett: Lectures

September 9, 2019
TITLE: Global aspects of the 3d-3d correspondence

ABSTRACT: We discuss various aspects of the 3d supersymmetric quantum field theories obtained by compactifying a stack of M5 branes on a three-manifold, arising in the so-called “3d-3d correspondence.” In particular, we emphasize the role of higher-form symmetries of the M5 brane theory, which provide a refinement of the 3d-3d correspondence related to the global structure of the 3d gauge theories. We focus in particular on the case where the three-manifold is a Seifert manifold, where we write 3d N=2 Lagrangians for these theories. The vacuum equations take the form of Bethe-ansatz type equations, which we solve in several examples. This leads to new tests of the 3d-3d correspondence, in particular, of the action of the higher symmetry on the set of vacua. We comment on implications for the N=1 3d-3d correspondence, arising from compactification on an associative cycle in a G_2 manifold.

Slides of lecture

Nelvis Fornasin: Lectures

September 9, 2019
TITLE: The eta invariant under cone-edge degeneration

ABSTRACT: I will discuss an analytic approach to the computation of the \bar\nu invariant introduced by Crowley, Goette and Nordström.
The \bar\nu invariant is made up of \eta invariants: following work by Sher, I will talk about the behaviour of these invariants under cone-edge degeneration of the underlying manifold. The results can be applied to the computation of the \bar\nu invariant of Joyce’s G_2 manifolds… with some restrictions.

Slides of lecture

Ronan Conlon: Lectures

September 9, 2019
TITLE: Classification results for expanding and shrinking gradient Kähler-Ricci solitons

ABSTRACT: A complete Kahler metric g on a Kahler manifold M is a “gradient Kahler-Ricci soliton” if there exists a smooth real-valued function f:M\to\mathbb{R} with \nabla f holomorphic such that \operatorname{Ric}(g)-\operatorname{Hess}(f)+\lambda g=0 for \lambda a real number. I will present some classification results for such manifolds. This is joint work with Alix Deruelle (Université Paris-Sud) and Song Sun (UC Berkeley).

Amihay Hanany: Lectures

September 9, 2019
TITLE: Hasse diagrams for symplectic singularities

ABSTRACT: Symplectic singularities appear in physics as the so called Higgs branches and Coulomb branches of supersymmetric gauge theories. They naturally form a structure of symplectic leaves with a partial order that can be depicted by a Hasse diagram.

The physical interpretation of this geometric structure is the so called “partial Higgs mechanism” where, on each leaf, the so-called “unbroken gauge group” is fixed. Simple examples of such symplectic singularities are closures of nilpotent orbits, and each leaf is associated with a smaller nilpotent orbit.

In this talk, we will explain these points, present the physical intuition, and suggest some results for Hasse diagrams of various Higgs branches that are of interest in some physical systems that arise in string theory.

Shing-Tung Yau: Lectures

September 8, 2019
TITLE: String duality and G2 manifolds

ABSTRACT: In this talk, I will begin by reviewing the mirror construction of G2 manifolds motivated by string duality (Gukov-Zaslow-Yau) and then discuss the physical interpretation of K stability of 3-dimensional Ricci-flat conical metrics (equivalently, Sasaki-Einstein metric and Kahler-Einstein metrics on Fano orbifolds) and how such metrics can be used to construct non-compact G2-manifolds.

Magdalena Larfors: Lectures

September 8, 2019
TITLE: Heterotic string theory and G2 structure manifolds

ABSTRACT: Please click to see abstract (PDF).
Slides of lecture