Talks

Research talks

Below is a selection of talks I have given on my research work.

Exceptional geometry of supersymmetric AdS vacua – View slides
In this talk, I show how exceptional field theory can be used to construct supersymmetric AdS vacua of 10-/11-dimensional supergravity, as well as classify and construct all possible consistent truncations with matter multiplets around the AdS vacua. In particular, I prove the half-maximally supersymmetric subcase of a conjecture by Gauntlett and Varela that all warped supersymmetric AdS_D vacua of 10-/11-dimensional supergravity admit a consistent truncation to D dimensions keeping only the gravitational supermultiplet. This talk focuses on the case of AdS₇ vacua of massive IIA and AdS₆ vacua of IIB supergravity. It is based on my papers

O-folds: Orientifolds and Orbifolds in Exceptional Field Theory – Blackboard talk
In this talk I show how exceptional field theory unifies orientifolds and orbifolds into a single object, an "O-fold", which corresponds to a discrete action of the exceptional group. I also show how the half-maximal formalism I developed can be used to capture the twisted sector living at the fixed point of the orientifold/orbifold action. The formalism also leads to a description of asymmetric orbifolds. The talk is based on my papers
- C. D. A. Blair, E. Malek and D. C. Thompson, O-folds: Orientifolds and Orbifolds in Exceptional Field Theory,
- E. Malek, Half-maximal supersymmetry from exceptional field theory.

Locally non-geometric fluxes and non-associativity in M-theory – View slides
In this talk I describe the non-perturbative generalisation of so-called "locally non-geometric" backgrounds of string theory, which are characterised by the fact that they are patched using string dualities and cannot be described as supergravity backgrounds. The perturbative version of these backgrounds have previously been analysed and there have been hints that string theory on such backgrounds shows signs of non-associativity. I conjecture a generalisation of the non-associativity in M-theory. A key feature is that certain momentum states are missing which is related to the Freed-Witten anomaly by string dualities. This talk is based on my papers

Exceptional field theory and half-maximal SUSY – View slides
In this talk, I show how exceptional field theory can be used to construct general half-maximally supersymmetric consistent truncations of 10-/11-dimensional supergravity, in particular those which cannot be obtained by starting with half-maximal supersymmetry in 10 dimensions, and prove the half-maximally supersymmetric subcase of a conjecture by Gauntlett and Varela that all warped supersymmetric AdS_D vacua of 10-/11-dimensional supergravity admit a consistent truncation to D dimensions keeping only the gravitational supermultiplet. This talk is based on my papers

1/2-maximal consistent truncations using exceptional field theory and the M-theory / heterotic duality – View slides
In this talk (aimed at experts in exceptional field theory, double field theory and generalised geometry), I show how exceptional field theory can be used to construct general half-maximally supersymmetric consistent truncations of 10-/11-dimensional supergravity, in particular those which cannot be obtained by starting with half-maximal supersymmetry in 10 dimensions. Moreover, I show that this method allows a reduction of exceptional field theory to heterotic double field theory, and how the duality between M-theory on K3 and heterotic string theory on T³ arises in exceptional field theory. An earlier and shorter version of this talk was given as an invited talk at the Workshop on "Geometry and Physics" at Schloss Ringberg on 24th November 2016 and has been published as conference proceedings. This talk is based on my papers

Non-geometric fluxes and non-associativity in M-theory – View slides
In this talk, I review non-geometric backgrounds in string theory, which are characterised by the fact that they are patched using string dualities and cannot be described as supergravity backgrounds, and describe the non-perturbative generalisation of so-called "locally non-geometric" backgrounds. The perturbative version of these backgrounds have previously been analysed and there have been hints that string theory on such backgrounds shows signs of non-associativity. I conjecture a generalisation of the non-associativity in M-theory. A key feature is that certain momentum states are missing which is related to the Freed-Witten anomaly by string dualities. This talk is based on my papers
- M. Günaydin, D. Lüst and E. Malek, Non-associativity in non-geometric string and M-theory backgrounds, the algebra of octonions and missing momentum modes,
- C. D. A. Blair and E. Malek, Geometry and fluxes of SL(5) exceptional field theory.

Exceptional field theories and gauged supergravities – Dualising consistent truncations – View slides
In this talk, I show how exceptional field theory can be used to easily construct consistent truncations of 10-/11-dimensional supergravity to maximally supersymmetric supergravities in lower dimensions. In particular, I show how certain consistent truncations of type IIA/IIB supergravity can be "dualised" to obtain a new consistent truncation, to a different gauged SUGRA, of type IIB/IIA supergravity. Two examples of this method are shown: I derive a new consistent truncation of IIB SUGRA on S³ using the previously known consistent truncation IIA SUGRA on S³, and I construct new consistent truncations of IIA/IIB SUGRA on products of 6-dimensional hyperboloids, H^p,q × H^r,s. The latter can be used to uplift two inequivalent dyonically gauged SO(4) × SO(2,2) ⋉ T¹⁶ 4-dimensional gauged SUGRAs which admit Minkowski vacua. The talk is based on my papers

Dualising consistent truncations: IIA/IIB on S³ – View slides
In this talk (aimed at experts in exceptional and double field theory and generalised geometry), I show how exceptional field theory can be used to "dualise" certain consistent truncations of type IIA/IIB supergravity to obtain new consistent truncations, to different gauged SUGRA, of type IIB/IIA supergravity. As an example, I derive a new consistent truncation of IIB SUGRA on S³ using the previously known consistent truncation IIA SUGRA on S³. The talk is based on my papers

Dualising consistent truncations: IIA/IIB on S³ – View slides
This is a slightly longer version of the above talk with the same title, but aimed at a general string theory audience. A shorter version of this talk was given as a parallel talk at the "String Theory Universe 2015" conference and has been published as conference proceedings. The talk is based on my papers

An introduction to double field theory and non-geometry – View slides, part I – View slides, part II
An introductory talk on double field theory. In this talk, I give an introduction to double field theory, a T-duality manifest rewriting of the low-energy supergravities of string theory, and explain what non-geometry means in the context of string theory. Then, I show how the bosonic degrees of freedom of type II supergravity are naturally rewritten in double field theory and how a double field theory action can be obtained. I show how to understand the geometry of double field theory and how it (and its M-theory extension) can be used to obtain a higher-dimensional origin for gauged supergravities. In part II, I discuss further recent results, for example the unification of type II theories in the M-theory analogue of double field theory, known as extended (now exceptional) field theory, and the action of timelike dualities. The talk is based on my papers

Non-specialist talks

I have also given talks on my work to non-specialist audiences:

Stringtheorie, Kompaktifizierungen und unser Universum (in German), a talk given at the Bruno H. Bürgel astronomical observatory Berlin in February 2020.
Abstract (in German): Was passierte in dem Big Bang, den Urprunsgsmoments unseres Universums, als alle Materie in einem winzigen Ort zusammengedrückt war? Was geschieht tief im Inneren von Schwarzen Löchern? Um diese Fragen zu beantworten, brauchen wir eine Theorie der Quantengravitation. Unsere am besten entwickelte Quantengravitationstheorie ist die Stringtheorie, in der alle Elementarteilchen aus winzigen vibrierenden Saiten (Strings) bestehen. Eine Vorhersage der Stringtheorie ist, dass unser Universum weitere 6 Dimensionen hat, die in einen kleinen Raum gekrümmt sind. Die Form dieser "Kompaktifizierungen" bestimmt die Physik, z.B. die Arten an Elementarteilchen und elementaren Kräfte, die wir in einem Stringtheorie Universum erleben würden. In diesem Vortrag werde ich diese Beziehung zwischen Physik und der Form der gekrümmten Dimensionen erläutern, und neue Bestrebungen präsentieren, um die Stringtheorie experimentell zu testen.
String Theory and Double Field Theory: Why small circles and big circles are the same, a talk given at the Peterhouse Graduate Symposium in November 2013.
Abstract: In everyday life, we think we understand the concept of size and that "small" and "big" are easily distinguishable. I will show why in string theory small and big circles are the same thing, why this gives string theory interesting properties and why we should care in the real world. I will then describe my research in double field theory and show how this naturally describes string theory by treating small and big circles in the same way.