Talks

Speakers

(Titles, abstracts and slides of talks below.)

Iosif Bena (IPhT Saclay)

The Amazing Supermaze

F1 strings added to N5 Type IIA NS5 branes, can decompose into N5 little strings, that can oscillate and carry momentum independently. The entropy of these N1 N5 little strings carrying Np unites of momentum reproduces exactly the entropy of the corresponding black hole.

We show that upon uplifting to M-theory and taking into account brane bending, these black-hole microstate configurations become super-mazes, which exhibit local supersymmetry enhancement: the full configuration preserves four supercharges, but upon zooming in at any location of the supermaze, the number of preserved supersymmetries is enhanced to 16; these 16 supercharges rotate as one moves at a different location, and only four of them are preserved throughout the solution.

Since objects exhibiting local supersymmetry enhancement are the fundamental building blocks of all known horizonless black-hole microstate geometries, this result makes us confident that the backreaction of the supermaze will give rise to smooth horizonless solutions that will reproduce the black-hole entropy.

Eric Bergshoeff (Groningen U.)

p-Brane Galilean and Carrol Symmetries

Galilei and Carroll symmetries have occurred in several recent investigations. In this talk I will discuss p-brane extensions of these symmetries. In particular, I will give a classification of p-brane Galilean and Carroll geometries and show how some of these geometries can be realized as special limits of general relativity.

Davide Cassani (INFN, Padua)

Higher-derivative corrections to the entropy of supersymmetric AdS5 black holes and their holographic match

The fundamental theory of quantum gravity is expected to manifest itself at low energies via a series of higher-derivative corrections to Einstein’s theory. Holography and supersymmetry provide a controlled scenario to study such corrections: through holography, quantum gravity in Anti de Sitter space has a rigorous definition in terms of a conformal field theory, while supersymmetry makes it possible to compute exact observables and make quantitative predictions. In this context, I will discuss how a CFT generating function known as the superconformal index provides a microscopic derivation of the entropy of five-dimensional supersymmetric black holes in AdS. I will illustrate how this match goes beyond the Bekenstein-Hawking area law and includes higher-derivative corrections.

Martin Cederwall (Chalmers U. Tech.)

The teleparallel complex

We formalise the teleparallel version of extended geometry (including gravity) by the introduction of a complex, the differential of which provides the linearised dynamics. The main point is the natural replace- ment of the two-derivative equations of motion by a differential which only contains terms of order 0 and 1 in derivatives. Second derivatives arise from homotopy transfer (elimination of fields with algebraic equations of motion). The formalism has the advantage of providing a clear consistency relation for the algebraic part of the differential, the “dualisation”, which then defines the dynamics of physical fields. It remains unmodified in the interacting BV theory, and the full non-linear models arise from covariantisation. A consequence of the use of the complex is that symmetry under local rotations becomes as good as manifest, instead of arising for a specific combination of tensorial terms, for less obvious reasons.

Daniel Grumiller (Vienna, Tech. U.)

Horizon Strings as 3d Black Hole Microstates

We propose that 3d black holes are an ensemble of tensionless null string states. These microstates typically have non-zero winding. We evaluate their partition function in the limit of large excitation numbers and show that their combinatorics reproduces the Bekenstein-Hawking entropy and its semiclassical logarithmic corrections. [2210.10794]

Falk Hassler (Wroclaw U.)

Supergeneralized geometry and dualities

Generalized Geometry has become a powerful tool to study solutions of supergravity and their transformation under duality symmetries of string and M-theory. Its success originates from unifying all bosonic symmetries, consisting of diffeomorphisms and form-field gauge transformations. This idea can be pushed further by including supersymmetry to obtain supergeneralized geometry. After reviewing its salient features, I show how it captures fermionic T-dualities and allows to describe integrable superstrings (called eta- and lambda-deformation) without the ambiguities one faces in generalized geometry.

Olaf Hohm (Humboldt U.)

Weakly constrained double field theory as the double copy of Yang-Mills

Double field theory was originally introduced as the subsector of closed string field theory on a toroidal background given by the massless fields together with all their massive Kaluza-Klein and winding modes, which are encoded in the dependence of the massless fields on doubled toroidal coordinates, subject to the so-called 'weak constraint'. This theory was constructed by Hull and Zwiebach in 2009 to cubic order in fields, but due to the weak constraint it is a highly non-trivial problem to extend this to quartic and higher order. In this I will explain the construction of weakly constrained double field theory to quartic order. To this end I will introduce the framework of homotopy algebras and explain how to construct double field theory as a double copy of the kinematic homotopy algebra of Yang-Mills theory.

Gabriel Larios (Texas A&M U.)

New families of AdS3 solutions in D=6 and D=10

I will describe new families of solutions in N=(1,1) supergravity in D=6 which uplift from half-maximal gauged supergravity in D=3 and are continuously connected to a 1/4-BPS configuration. Using recent Exceptional Field Theory techniques, I will discuss the Kaluza-Klein spectrum on these vacua, which shows that, for a range of parameters, the solutions are perturbatively stable despite non-supersymmetric. These families will be later uplifted to type IIB solutions of AdS3xS3xT4 type and some results on their D=10 spectrum will be presented.

Yolanda Lozano (Oviedo U.)

Low dimensional holography, defects and string dualities

We will review recent constructions of AdS3 and AdS2 solutions that find an interpretation as holographic duals of defects within higher dimensional CFTs. We will discuss the role played by string dualities in these constructions.

Emanuel Malek (Humboldt U.)

Kaluza-Klein Spectrometry for String Theory Compactifications

I will present a powerful new method that for the first time allows us to compute the Kaluza-Klein spectrum of a large class of string theory compactifications, including those arising in maximal gauged supergravities and beyond. This includes geometries with little to no remaining (super-)symmetries, completely inaccessible by previous methods. I will show how these insights can be used to holographically compute the anomalous dimensions of protected and unprotected operators in strongly-coupled CFTs, as well as to 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. We will see the importance of higher Kaluza-Klein modes to the physics of string compactifications, e.g. in realising the compactness of moduli spaces, and in destabilising vacua that appear to be stable in lower-dimensional supergravities. If time permits, I will comment on ongoing work extending these methods to capturing cubic interactions in supergravity, where we will encounter a surprising new structure that is inherited from the consistent truncation to maximal gauged supergravity.

Edvard Musaev (Moscow, MIPT)

Deforming supergravity backgrounds by compact isometries

The well known example of a bi-vector Yang-Baxter deformation is the supergravity background dual to the Leigh-Strassler family of exactly marginal deformation of the d=4 N=4 SYM preserving N=1 SUSY. These are abelian deformation constructed on U(1)xU(1) isometries. A theorem says that there are no solutions to classical Yang-Baxter equation for r-matrices from algebras of compact isometry groups. This talk is devoted to a tri-vector generalization of such deformations where the theorem does not apply. This allows to consider non-abelian deformations on compact isometries of the initial background and generate families of exactly marginal deformation of conformal theories. Explicit examples are given by deformations of the AdS7xS4 background dual to the D=6 N=(2,0) SCFT

Jakob Palmkvist (Orebro U.)

Tensor hierarchy algebras: the first ten years

I will summarise a decade of the infinite-dimensional Lie superalgebras known as tensor hierarchy algebras: their constructions and their applications to gauged supergravity and extended geometry.

Michela Petrini (LPTHE, Paris)

What can generalised geometry say about N=1 SCFT’s

Generalised geometry provides a unified approach to study the geometries dual to N=1 SCFT’s and hence provides a handle on their properties.

In this talk I will summarise the results obtained in recent years in type IIB supergravities and the dual N=1 SCFT”s.

Joris Raeymaekers ( Inst. Phys., Prague)

Wormholes and surface operators in ensemble holography

Euclidean wormhole contributions to the path integral have recently received attention, ranging from excitement (in the context of the information paradox) to bewilderment (in the context of the factorization problem and ensemble holography). Simple toy models, such as Narain duality, can help clear up some of the puzzles related to ensemble holography. Here I will discuss arguably the simplest models of this kind, where the ensemble is a discrete set of rational compact boson CFTs. In this context we can give a clear bulk interpretation of a class of `exotic' wormholes, needed for consistency of the duality, in terms of topological surface defects introduced by Kapustin and Saulina.

Jan Rosseel (Boskovic Inst., Zagreb)

Geometries for non-relativistic strings and branes.

In this talk, I will discuss the target space geometries that non-relativistic strings and branes propagate in. These geometries can be obtained by taking a non-relativistic limit in which the speed of light in the directions transverse to the string/brane-worldvolume is sent to infinity and correspond to particular generalizations of Newton-Cartan geometry. I will discuss their metric and metric compatible connection structure. I will argue that generic metric compatible connections have intrinsic torsion. I will show the various constraints that can be imposed consistently on the intrinsic torsion and clarify their geometrical meaning.

Augusto Sagnotti (Scuola Normale Superiore, Pisa)

Non-Supersymmetric Strings and Some of their (In)Stabilities

I shall address some of the main lessons drawn so far from the tadpole potentials that emerge in the ten–dimensional strings with broken supersymmetry. These lessons include weak-string-coupling cosmologies that appear to provide clues on the onset of the inflation and spontaneous compactifications to lower–dimensional Minkowski spaces at corresponding length scales. The cosmological solutions exhibit an intriguing “instability of isotropy” that, if taken at face value, would point to an accidental origin of compactification. On the other hand, while highly symmetric AdS × S vacuum solutions driven by fluxes and tadpole potentials are unstable due to mixings induced by their internal fluxes, the original Dudas–Mourad solution is perturbatively stable, and we have gathered detailed evidence that instabilities can be held under control in a similar class of type–IIB compactifications to Minkowski space where the string coupling is everywhere weak. These vacua involve internal intervals, and a careful scrutiny of the possible self—adjoint boundary conditions plays a central role in the analysis.

Shahin Sheikh-Jabbari (IPM, Tehran)

Hydro/Thermo Dynamics at Causal Boundaries, Examples in 3d Gravity.

We study 3-dimensional gravity on a spacetime bounded by a generic 2-dimensional causal surface, the boundary degrees of freedom, boundary charges and their algebra. Three of the boundary charges extend and generalize the Brown-York are canonical conjugates of boundary metric components and naturally give rise to a fluid description at the causal boundary. We show that the boundary charges besides the causal boundary hydrodynamic description, also admit a thermodynamic description with a natural (geometric) causal boundary temperature and angular velocity. When the causal boundary is the asymptotic boundary of the 3d AdS or flat space, the hydrodynamic description respectively recovers an extension of the known conformal or conformal-Carrollian asymptotic hydrodynamics. When the causal boundary is a generic null surface.

Kelly Stelle (Imperial Coll.)

Supergravities on Branes

Supergravity brane solutions allow for a generalised type of Kaluza-Klein consistent dimensional reduction onto brane worldvolumes. The seed example of this is the replacement of a flat worldvolume metric by a Ricci-flat metric, i.e. an N=0 reduction. For an underlying "vacuum" worldvolume preserving N unbroken supersymmetries, such a braneworld consistent reduction can be extended to a full nonlinear N-extended supergravity on the worldvolume. This is seen in a number of braneworld examples, and suggests that there may be a general theorem, including possibly also Calabi-Yau reductions.

Per Sundell (Biobio U.)

Higher Spin Quantum Gravity and Noncommutative AKSZ Sigma models

AKSZ sigma models in which both sources and targets are noncommutative geometries provide a natural framework for the BV quantization of Vasiliev's higher spin gravities including generating functionals for amplitudes in terms of dual conformal higher spin gravities.

Alessandro Tomasiello (Milan Bicocca U.)

General bounds on Kaluza–Klein masses

The Kaluza–Klein (KK) spectrum is an important feature of a gravity compactification, but it is hard to compute. In this talk I will describe several new theorems on the masses of the KK spin-two fields, valid for a vast class of gravity compactifications and often even in the presence of brane singularities. The techniques come mostly from the mathematical field of optimal transport, with intriguing connections to the convexity of entropy. I will highlight some applications to the issue of scale separation and to gravity localization.

Mario Trigiante (Turin Polytechnic)

Webs of Marginally Connected Vacua in Gauged Supergravity

We illustrate the recent construction of gauged extended supergravity models in four dimensions featuring webs of anti-de Sitter vacua, preserving different amounts of supersymmetries or no supersymmetry at all, connected by flat directions of the scalar potential.

One class of vacua was found in maximal gauged supergravity and effectively describes S-fold backgrounds of Type IIB superstring theory. Some of the flat directions are interpreted in terms global geometric properties of the internal compact manifold.

The second class of vacua was found in a gauged N=3 model with gauge group SO(3) x SU(3). As opposed to the first class of solutions, their uplift to string/M-theory backgrounds is still an open problem.

We briefly touch upon the possible interpretation of the flat directions in terms of exactly marginal deformations of the dual (super-) conformal field theory.

Page updated

Google Sites

Report abuse