# Talks

## Colloquium talks

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

**Exceptional Field Theory and applications to the AdS/CFT correspondence**– View slides

Target audience: researchers working on QFT.

Abstract: The AdS/CFT correspondence is a powerful tool for studying strongly coupled QFTs by performing computations in string theory and its low energy limit, supergravity. I will review Exceptional Field Theory, a formalism that unifies gravitational and flux degrees of freedom of supergravity, and thereby makes a large exceptional symmetry group manifest. This large symmetry group simplifies many complicated calculations in AdS backgrounds, such as constructing consistent truncations or computing the spectrum of linearised fluctuations around AdS vacua. I will show how this can be used to gain insights into strongly coupled QFTs. Finally, it time permits, I will discuss applications to non-supersymmetric AdS vacua.**Listening to the shape of string theory's extra dimensions**– View slides

Target audience: general physics audience.

Abstract: All applications of string theory, whether in modelling fundamental particle physics interactions or in studying strongly-coupled quantum field theories via holography, require some of string theory's 10 dimensions to be "compactified", i.e. curled up into a small space. The shape of these compactified dimensions determines the physics, such as the spectrum of particles, observed in the remaining large dimensions. This is analogous to how the shape of instruments determines the sound of notes played. However, in practice, computing the spectrum for realistic compactifications reduces to a fiendishly complicated exercise in harmonic analysis. I will present new methods of performing this analysis and what this teaches us about the physics of string theory.

## Research talks

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

**Applications of Exceptional Field Theory to the AdS/CFT correspondence**– View slides

In this talk, I will show how Exceptional Field Theory (ExFT), a reformulation of 10-/11-d supergravity that unifies fluxes and geometry, gives us powerful new tools for the AdS/CFT correspondence. In particular, I will review how ExFT allows us to uplift lower-dimensional toy models ("gauged supergravities") to fully-fledged 10-/11-d geometries. Moreover, using ExFT we can, for the first time, compute the entire Kaluza-Klein spectrum around AdS geometries with little to no remaining (super-)symmetries, completely inaccessible by standard methods. I will show how these insights can be used to compute the anomalous dimensions of protected and unprotected operators in strongly-coupled CFTs, as well as study global properties of their conformal manifolds. I will also show how the method can be used to determine the perturbative stability of non-supersymmetric AdS vacua. This reveals that tachyons can arise from higher Kaluza-Klein modes not visible in lower-dimensional gauged supergravities. Intriguingly, there are also classes of fully perturbatively stable non-supersymmetric AdS vacua in supergravity. It is based on my papers- M. Galli and
**E. Malek**, Consistent truncations to 3-dimensional supergravity, - A. Giambrone, A. Guarino,
**E. Malek**, H. Samtleben, C. Sterckx and M. Trigiante, Holographic evidence for nonsupersymmetric conformal manifolds, - G. Josse,
**E. Malek**, M. Petrini and D. Waldram, The higher-dimensional origin of five-dimensional N = 2 gauged supergravities, - A. Giambrone,
**E. Malek**, H. Samtleben and M. Trigiante, Global Properties of the Conformal Manifold for S-Fold Backgrounds, **E. Malek**and V. Vall Camell, Consistent truncations around half-maximal AdS_{5}vacua of 11-dimensional supergravity,- N. Bobev,
**E. Malek**, B. Robinson, H. Samtleben and J. van Muiden, Kaluza-Klein Spectroscopy for the Leigh-Strassler SCFT, - A. Guarino,
**E. Malek**and H. Samtleben, Stable non-supersymmetric Anti-de Sitter vacua of massive IIA supergravity, **E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry from Exceptional Field Theory,**E. Malek**, H. Nicolai and H. Samtleben, Tachyonic Kaluza-Klein modes and the AdS swampland conjecture,**E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry for Supergravity,**E. Malek**, H. Samtleben and V. Vall Camell, Supersymmetric AdS_{7}and AdS_{6}vacua and their consistent truncations with vector multiplets,**E. Malek**, H. Samtleben and V. Vall Camell, Supersymmetric AdS_{7}and AdS_{6}vacua and their minimal consistent truncations from exceptional field theory,**E. Malek**, Half-maximal supersymmetry from exceptional field theory.

- M. Galli and
**Kaluza-Klein Spectrometry for String Theory Compactifications**– View slides

In this talk, I will present a powerful new method for computing the Kaluza-Klein spectrum of string theory compactifications. This includes geometries with little to no remaining symmetries, hardly accessible to standard methods. I will discuss various applications of this method, including to non-supersymmetric AdS_{4}vacua. As I will show, some of these AdS vacua are unstable due to tachyonic Kaluza-Klein modes, while others can be proven to be perturbatively stable. Finally, I will also discuss applications to supersymmetric AdS vacua and the AdS/CFT correspondence. It is based on my papers- A. Giambrone,
**E. Malek**, H. Samtleben and M. Trigiante, Global Properties of the Conformal Manifold for S-Fold Backgrounds, - N. Bobev,
**E. Malek**, B. Robinson, H. Samtleben and J. van Muiden, Kaluza-Klein Spectroscopy for the Leigh-Strassler SCFT, - A. Guarino,
**E. Malek**and H. Samtleben, Stable non-supersymmetric Anti-de Sitter vacua of massive IIA supergravity, **E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry from Exceptional Field Theory,**E. Malek**, H. Nicolai and H. Samtleben, Tachyonic Kaluza-Klein modes and the AdS swampland conjecture,**E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry for Supergravity.

- A. Giambrone,
**A Kaluza-Klein Spectrometer from Exceptional Field Theory**– View slides, recording

In this talk (aimed at experts in exceptional field theory, double field theory and generalised geometry), I will show how exceptional field theory gives us a powerful new method for computing the Kaluza-Klein spectrum of string theory compactifications. In particular, we can easily compute the Kaluza-Klein spectrum for any vacuum of an N=8 gauged supergravity arising from a consistent truncation. This includes various AdS vacua in 4 and 5 dimensions, preserving few or no (super)symmetries. I will apply this new method to compute the Kaluza-Klein spectrum of the non-supersymmetric SO(3) x SO(3) invariant AdS_{4}vacuum of 11-dimensional supergravity, which is perturbatively stable within N=8 gauged supergravity. I will show that, nonetheless, the higher Kaluza-Klein modes become tachyonic so that this non-supersymmetric AdS_{4}vacuum is unstable within 11-dimensional supergravity. This represents the first example of unstable higher Kaluza-Klein modes. It is based on my papers**E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry from Exceptional Field Theory,**E. Malek**, H. Nicolai and H. Samtleben, Tachyonic Kaluza-Klein modes and the AdS swampland conjecture,**E. Malek**and H. Samtleben, Kaluza-Klein Spectrometry for Supergravity.

**Exceptional geometry of supersymmetric AdS vacua and their consistent truncations**– 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 AdS_{7}vacua of massive IIA and AdS_{6}vacua of IIB supergravity. It is based on my papers**E. Malek**, H. Samtleben and V. Vall Camell, Supersymmetric AdS_{7}and AdS_{6}vacua and their consistent truncations with vector multiplets,**E. Malek**, H. Samtleben and V. Vall Camell, Supersymmetric AdS_{7}and AdS_{6}vacua and their minimal consistent truncations from exceptional field theory,**E. Malek**, Half-maximal supersymmetry from exceptional field theory,**E. Malek**, From Exceptional Field Theory to Heterotic Double Field Theory via K3,**E. Malek,**7-dimensional N=2 Consistent Truncations using SL(5) Exceptional Field Theory.

**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.

- C. D. A. Blair,
**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- D. Lüst,
**E. Malek**and M. Syväri, Locally non-geometric fluxes and missing momenta in M-theory, - D. Lüst,
**E. Malek**and R. Szabo, Non-geometric Kaluza-Klein monopoles and magnetic duals of M-theory R-flux backgrounds, - 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.

- D. Lüst,
**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 T^{3}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.

- M. Günaydin, D. Lüst and
**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 S^{3}using the previously known consistent truncation IIA SUGRA on S^{3}, 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) ⋉ T^{16}4-dimensional gauged SUGRAs which admit Minkowski vacua. The talk is based on my papers**E. Malek**and H. Samtleben, Ten-dimensional origin of Minkowski vacua in N=8 supergravity,**E. Malek**and H. Samtleben, Dualising consistent IIA/IIB truncations,- C. D. A. Blair and
**E. Malek**, Geometry and fluxes of SL(5) exceptional field theory, - C. D. A. Blair,
**E. Malek**and J.-H. Park, M-theory and Type IIB from a Duality Manifest Action, - D. S. Berman, C. D. A. Blair,
**E. Malek**and M. J. Perry, The O_{D,D}Geometry of String Theory.

**Dualising consistent truncations: IIA/IIB on S**– View slides^{3}

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 S^{3}using the previously known consistent truncation IIA SUGRA on S^{3}. The talk is based on my papers**E. Malek**and H. Samtleben, Dualising consistent IIA/IIB truncations,- C. D. A. Blair and
**E. Malek**, Geometry and fluxes of SL(5) exceptional field theory, - C. D. A. Blair,
**E. Malek**and J.-H. Park, M-theory and Type IIB from a Duality Manifest Action, - D. S. Berman, C. D. A. Blair,
**E. Malek**and M. J. Perry, The O_{D,D}Geometry of String Theory.

**Dualising consistent truncations: IIA/IIB on S**– View slides^{3}

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**E. Malek**and H. Samtleben, Dualising consistent IIA/IIB truncations,- C. D. A. Blair and
**E. Malek**, Geometry and fluxes of SL(5) exceptional field theory, - C. D. A. Blair,
**E. Malek**and J.-H. Park, M-theory and Type IIB from a Duality Manifest Action, - D. S. Berman, C. D. A. Blair,
**E. Malek**and M. J. Perry, The O_{D,D}Geometry of String Theory.

**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- C. D. A. Blair,
**E. Malek**and J.-H. Park, M-theory and Type IIB from a Duality Manifest Action. - D. S. Berman, C. D. A. Blair,
**E. Malek**and M. J. Perry, The O_{D,D}Geometry of String Theory, **E. Malek**, Timelike Dualities in Generalised Geometry.

- C. D. A. Blair,

## Non-specialist talks

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

- String theory, compactifications and our universe (in German), a talk given at the Bruno H. Bürgel astronomical observatory Berlin in February 2020.

German title: Stringtheorie, Kompaktifizierungen und unser Universum

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.