arXiv subjects

Henning Samtleben

Publications and source records attributed to Henning Samtleben.

At least 37 records · Page 2Linked to original sources

arXiv2023

Consistent sphere reductions of gravity to two dimensions

Consistent reductions of higher-dimensional (matter-coupled) gravity theories on spheres have been constructed and classified in an important paper by Cvetič, Lü and Pope. We close a gap in the classification and study the case when the resulting lower-dimensional theory is two-dimensional. We construct the consistent reduction of Einstein-Maxwell-dilaton gravity on a $d$-sphere $S^d$ to two-dimensional dilaton-gravity coupled to a gauged sigma model with target space ${\rm SL}(d+1)/{\rm SO}(d+1)$. The truncation contains solutions of type AdS$_2\times Σ_d$ where the internal space $Σ_d$ is a deformed sphere. In particular, the construction includes the consistent truncation around the near-horizon geometry of the boosted Kerr string. In turn, we find that an AdS$_2\times S^d$ background with the round $S^d$ within a consistent truncation requires $d>3$ and an additional cosmological term in the higher-dimensional theory.

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arXiv2023

A holographic RG flow from the squashed to the round $S^7$

We construct and analyze the domain wall solution in $D=11$ supergravity connecting the $N=1$, AdS$_4\times S_{\rm squashed}^7$ vacuum to the $N=8$, AdS$_4\times S_{\rm round}^7$ vacuum. This domain wall describes the holographic renormalization group flow from an ${\rm Sp}(2)\times {\rm Sp}(1)$ symmetric UV fixed point to the ${\rm SO}(8)$ symmetric IR fixed point. It breaks all supersymmetries which are (partially) restored at its endpoints. We show how recent techniques from exceptional field theory allow us to compute the quadratic couplings of all Kaluza-Klein fluctuations around the domain wall background, encoding all two-point correlators along the holographic RG flow.

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arXiv2023

Minimal Massive Supergravity

Minimal massive gravity in three dimensions propagates a single massive spin-2 mode around an AdS vacuum. It is distinguished by allowing for vacua with positive central charges of the asymptotic conformal algebra and a bulk graviton of positive energy. We present a new action for the model (and its higher order extensions) in terms of a dreibein and an independent spin connection. From this, we construct its supersymmetric extension. Surprisingly, all vacua complying with bulk and boundary unitarity appear to break supersymmetry spontaneously. In contrast, all supersymmetric vacua have a negative central charge whenever the bulk graviton has positive energy.

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arXiv2023

Holographic Evidence for Non-Supersymmetric Conformal Manifolds

We provide the first holographic evidence for the existence of a non-supersymmetric conformal manifold arising from exactly marginal but supersymmetry-breaking deformations of a superconformal three-dimensional field theory. In particular, we construct a 2-parameter non-supersymmetric deformation of a supersymmetric AdS non-geometric background in Type IIB string theory. We prove that the non-supersymmetric backgrounds are perturbatively stable and also do not suffer from various non-perturbative instabilities. Finally, we argue that diffeomorphism symmetry protects our solutions against higher-derivative string corrections.

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arXiv2023

Kaluza-Klein Spectrometry beyond Consistent Truncations: The Squashed $S^7$

We show how to use Exceptional Field Theory to compute the full Kaluza-Klein spectra of 10- and 11-dimensional supergravity around deformations of backgrounds of maximal gauged supergravity by scalar modes that do not form part of the consistent truncation. This includes deformations of AdS$_4 \times S^7$ and AdS$_5 \times S^5$ by modes that are not part of the ${\cal N}=8$ supermultiplet. As an application, we compute the full Kaluza-Klein spectrum of the ${\cal N}=1$ and ${\cal N}=0$ squashed $S^7$. In this example, all conformal dimensions are captured by a universal formula in terms of the Casimir operators and additional quantum numbers which organise the spectrum.

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arXiv2022

U-duality and $α'$ corrections in three dimensions

We consider the target space theory of bosonic and heterotic string theory to first order in $α'$ compactified to three dimensions, using a formulation that is manifestly T-duality invariant under ${\rm O}(d,d,\mathbb{R})$ with $d=23$ and $d=7$, respectively. While the two-derivative supergravity exhibits a symmetry enhancement to the U-duality group ${\rm O}(d+1,d+1)$, the continuous group is known to be broken to ${\rm O}(d,d,\mathbb{R})$ by the first $α'$ correction. We revisit this observation by computing the full effective actions in three dimensions to first order in $α'$ by dualizing the vector gauge fields. We give a formally ${\rm O}(d+1,d+1)$ invariant formulation by invoking a vector compensator, and we observe a chiral pattern that allows one to reconstruct the bosonic action from the heterotic action. Furthermore, we obtain a particular massive deformation by integrating out the external $B$ field. This induces a novel Chern-Simons term based on composite connections that, remarkably, is ${\rm O}(d+1,d+1)$ invariant to leading order in the deformation parameter.

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arXiv2022

Supersymmetric action for 6D $(4,0)$ supergravity

We give a linearized but otherwise complete supersymmetric action for ${\cal N}=(4,0)$ supergravity in six dimensions, using a Kaluza-Klein-type $5+1$ split of coordinates and fields. We provide in particular a significantly simplified version of the bosonic action derived by us recently. This formulation employs fields that are no longer irreducible, subject to a local Lorentz invariance, which in turn simplifies the supersymmetry transformations including the exotic gravitino.

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arXiv2022

A note on the third way consistent deformation of Yang-Mills theory

Three-dimensional Yang-Mills theory allows for a deformation quadratic in the field strengths which can not be integrated to a local action without auxiliary fields. Yet, its covariant divergence consistently vanishes after iterating the equation, realizing a spin-1 analogue of `minimal massive gravity', which has been dubbed `third way consistent'. In this note, we show that after dualization of the three-dimensional gauge fields, the model possesses a natural action as a Chern-Simons coupled gauged sigma model. In this dual formulation, coupling to matter and to gravity becomes straightforward. As a direct application, we derive the coupling of the model to N=1 supergravity.

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arXiv2022

Triality and the consistent reductions on ${\rm AdS}_3\times S^3$

We study compactifications on ${\rm AdS}_3\times S^3$ and deformations thereof. We exploit the triality symmetry of the underlying duality group ${\rm SO}(4,4)$ of three-dimensional supergravity in order to construct and relate new consistent truncations. For non-chiral $D=6$, ${\cal N}_{\rm 6d}=(1,1)$ supergravity, we find two different consistent truncations to three-dimensional supergravity, retaining different subsets of Kaluza-Klein modes, thereby offering access to different subsectors of the full nonlinear dynamics. As an application, we construct a two-parameter family of ${\rm AdS}_3\times M^3$ backgrounds on squashed spheres preserving ${\rm U}(1)^2$ isometries. For generic value of the parameters, these solutions break all supersymmetries, yet they remain perturbatively stable within a non-vanishing region in parameter space. They also contain a one-parameter family of ${\cal N}=(0,4)$ supersymmetric ${\rm AdS}_3\times M^3$ backgrounds on squashed spheres with ${\rm U}(2)$ isometries. Using techniques from exceptional field theory, we determine the full Kaluza-Klein spectrum around these backgrounds.

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arXiv2021

Global Properties of the Conformal Manifold for S-Fold Backgrounds

We study a one-parameter family of $\mathcal{N}=2$ anti-de Sitter vacua with ${\rm U}(1)^2$ symmetry of gauged four-dimensional maximal supergravity, with dyonic gauge group $[{\rm SO}(6)\times {\rm SO}(1,1)]\ltimes \mathbb{R}^{12}$. These backgrounds are known to correspond to Type IIB S-fold solutions with internal manifold of topology $S^1\times S^5$. The family of AdS$_4$ vacua is parametrized by a modulus $χ$. Although $χ$ appears non-compact in the four-dimensional supergravity, we show that this is just an artefact of the four-dimensional description. We give the 10-dimensional geometric interpretation of the modulus and show that it actually has periodicity of $\frac{2π}{T}$, which is the inverse radius of $S^1$. We deduce this by providing the explicit $D=10$ uplift of the family of vacua as well as computing the entire modulus-dependent Kaluza-Klein spectrum as a function of $χ$. At the special values $χ=0$ and $χ=\fracπ{T}$, the symmetry enhances according to ${\rm U}(1)^2\rightarrow{\rm U}(2)$, giving rise however to inequivalent Kaluza-Klein spectra. At $χ=\fracπ{T}$, this realizes a bosonic version of the "space invaders" scenario with additional massless vector fields arising from formerly massive fields at higher Kaluza-Klein levels.

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arXiv2021

Kaluza-Klein Spectroscopy for the Leigh-Strassler SCFT

We apply recently developed tools from exceptional field theory to calculate the full Kaluza-Klein spectrum of the AdS$_5$ Pilch-Warner solution of type IIB supergravity. Through the AdS/CFT correspondence this yields detailed information about the spectrum of protected and unprotected operators of the four-dimensional $\mathcal{N}=1$ Leigh-Strassler SCFT, in the planar limit. We also calculate explicitly the superconformal index of the SCFT in this limit and show that it agrees precisely with the spectrum of protected operators in the supergravity calculation.

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arXiv2021

E$_9$ exceptional field theory II. The complete dynamics

We construct the first complete exceptional field theory that is based on an infinite-dimensional symmetry group. E$_9$ exceptional field theory provides a unified description of eleven-dimensional and type IIB supergravity covariant under the affine Kac-Moody symmetry of two-dimensional maximal supergravity. We present two equivalent formulations of the dynamics, which both rely on a pseudo-Lagrangian supplemented by a twisted self-duality equation. One formulation involves a minimal set of fields and gauge symmetries, which uniquely determine the entire dynamics. The other formulation extends $\mathfrak{e}_9$ by half of the Virasoro algebra and makes direct contact with the integrable structure of two-dimensional supergravity. Our results apply directly to other affine Kac-Moody groups, such as the Geroch group of general relativity.

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arXiv2021

Stable non-supersymmetric Anti-de Sitter vacua of massive IIA supergravity

Stable non-supersymmetric Anti-de Sitter (AdS) vacua of string theory are widely believed not to exist. In this letter, we analytically compute the full bosonic Kaluza-Klein spectrum around the ${\rm G_2}$-invariant non-supersymmetric $\textrm{AdS}_4$ solution of massive IIA supergravity, and show that it is perturbatively stable. We also provide evidence that six other non-supersymmetric $\textrm{AdS}_4$ solutions of massive IIA supergravity are perturbatively stable. Since previous studies have indicated that these AdS vacua may also be non-perturbatively stable, our findings pose a challenge to the Swampland Conjecture.

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arXiv2020

Kaluza-Klein Spectrometry from Exceptional Field Theory

Exceptional field theories yield duality-covariant formulations of higher-dimensional supergravity. They have proven to be an efficient tool for the construction of consistent truncations around various background geometries. In this paper, we demonstrate how the formalism can moreover be turned into a powerful tool for computing the Kaluza-Klein mass spectra around these backgrounds. Most of these geometries have little to no remaining symmetries and their spectra are accessible to standard methods only in selected subsectors. The present formalism not only grants access to the full Kaluza-Klein spectra but also provides the scheme to identify the resulting mass eigenstates in higher dimensions. As a first illustration, we rederive in compact form the mass spectrum of IIB supergravity on $S^5$. We further discuss the application of our formalism to determine the mass spectra of higher Kaluza-Klein multiplets around the warped geometries corresponding to some prominent ${\cal N}=2$ and ${\cal N}=0$ AdS vacua in maximal supergravity.

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arXiv2020

Tachyonic Kaluza-Klein modes and the AdS swampland conjecture

We compute the Kaluza-Klein spectrum of the non-supersymmetric SO(3)$\,\times\,$SO(3)-invariant AdS$_4$ vacuum of 11-dimensional supergravity, whose lowest-lying Kaluza-Klein modes belong to a consistent truncation to 4-dimensional ${\cal N}=8$ supergravity and are stable. We show that, nonetheless, the higher Kaluza-Klein modes become tachyonic so that this non-supersymmetric AdS$_4$ vacuum is perturbatively unstable within 11-dimensional supergravity. This represents the first example of unstable higher Kaluza-Klein modes and provides further evidence for the AdS swampland conjecture, which states that there are no stable non-supersymmetric AdS vacua within string theory. We also find 27 infinitesimal moduli amongst the Kaluza-Klein modes, which hints at the existence of a family of non-supersymmetric AdS$_4$ vacua.

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arXiv2020

Toward Exotic 6D Supergravities

We investigate exotic supergravity theories in 6D with maximal (4,0) and (3,1) supersymmetry, which were conjectured by C. Hull to exist and to describe strong coupling limits of ${\cal N}=8$ theories in 5D. These theories involve exotic gauge fields with non-standard Young tableaux representations, subject to (self-)duality constraints. We give novel actions in a 5+1 split of coordinates whose field equations reproduce those of the free bosonic (4,0) and (3,1) theory, respectively, including the (self-)duality relations. Evidence is presented for a master exceptional field theory formulation with an extended section constraint that, depending on the solution, produces the (4,0), (3,1) or the conventional (2,2) theory. We comment on the possible construction of a fully non-linear master exceptional field theory.

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arXiv2020

Duality Invariance and Higher Derivatives

We dimensionally reduce the spacetime action of bosonic string theory, and that of the bosonic sector of heterotic string theory after truncating the Yang-Mills gauge fields, on a $d$-dimensional torus including all higher-derivative corrections to first order in $α'$. A systematic procedure is developed that brings this action into a minimal form in which all fields except the metric carry only first order derivatives. This action is shown to be invariant under ${\rm O}(d,d,\mathbb{R})$ transformations that acquire $α'$-corrections through a Green-Schwarz type mechanism. We prove that, up to a global pre-factor, the first order $α'$-corrections are uniquely determined by ${\rm O}(d,d,\mathbb{R})$ invariance.

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arXiv2020

Kaluza-Klein Spectrometry for Supergravity

Exceptional field theories yield duality covariant formulations of supergravity. We show that they provide a highly efficient tool to compute the Kaluza-Klein mass spectra associated to compactifications around various background geometries relevant for string theory and holographic applications. This includes geometries with little to no remaining symmetries, hardly accessible to standard methods. As an illustration, we work out the masses of some higher Kaluza-Klein multiplets around warped geometries corresponding to some prominent ${\cal N} = 2$ supersymmetric AdS vacua in maximal supergravity.

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