Iberian Strings 2023

11 Jan 2023, 01:00 → 13 Jan 2023, 23:59 Europe/Madrid

Universidad de Murcia, Campus de la Merced (Murcia, Spain)

Fernández-Melgarejo, José Juan, Molina, Javi, Torrente-Luján, Emilio, Strings 2023, Iberian (Universidad de Murcia)

 

Iberian Strings 2023 is the 15th-installment of the annual meeting of the Spanish and Portuguese String Theory community, where recent developments in the field of supergravity, strings, branes and gauge theory are discussed. 

 

The three day meeting will have 6 one hour invited talks, as well as contributed talks, that center around the latest developments in String Theory, the AdS/CFT correspondence, Quantum Gravity and Quantum Field Theories as well as the profound relations among them. The workshop is structured in a discussion-friendly schedule and located in very friendly surroundings, with the aim of creating the ideal environment for scientific discussion.

 

The conference will be held on-site at the Paraninfo de la Universidad de Murcia, which is located at the city center and 70 km far from the Mediterranean Sea.

 

 

Please have a look at the Transportation section on how to travel to Murcia and the Accommodation section to obtain some special rates for the participants of this meeting.

 

 

 

Invited Speakers

• de Boer, Jan (Universiteit van Amsterdam)
• Guica, Monica (IPhT, Saclay)
• Magán, Javier (University of Pennsylvania)
• Montero, Miguel (Harvard University)
• Pedraza, Juan (IFT-CSIC/UAM)
• Pimentel, Guilherme (Scuola Normale Superiore, Pisa)

 

Public Talk: "La lencería del cosmos"

 

 

The earlier meetings in the Iberian Strings series were held in Gijón '22,  Lisbon '21, Santiago de Compostela '20, Barcelona '19, Granada '18, Lisbon'17, Madrid '16, Salamanca '15, Palencia '14, Lisbon'13, Bilbao '12, Valencia '11, Oporto '10, Gijón '09.

 

Scientific Committee

• Bandos, Igor (EHU/UPV)
• Costa, Miguel (Universidade do Porto)
• Edelstein, José (Universidade Santiago Compostela)
• Emparan, Roberto (ICREA/Universitat de Barcelona)
• Hernández, Rafael (Universidad Complutense Madrid)
• Janssen, Bert (Universidad de Granada)
• Lledó, María A. (IFIC-CSIC/Universitat de Valencia)
• Lopes-Cardoso, Gabriel (Universidade Tecnica Lisboa)
• Lozano, Yolanda (ICTEA/Universidad de Oviedo)
• Marchesano, Fernando (IFT-CSIC/UAM)
• Mateos, David (ICREA/Universitat de Barcelona)
• Ortín, Tomás (IFT-CSIC/UAM)
• Vázquez-Mozo, Miguel Ángel (Universidad de Salamanca)

 

Organizing Committee:

• Cardona, Biel (Universidad de Murcia)
• Fernandez-Melgarejo, Jose J. (Universidad de Murcia)
• Marrani, Alessio (Universidad de Murcia)
• Molina-Vilaplana, Javier (Universidad Politécnica Cartagena)
• Romano, Luca (Universidad de Murcia)
• Rosabal, J. Alejandro (Universidad de Murcia)
• Torrente-Lujan, Emilio (Universidad de Murcia)

 

 Technical Organizing Committee:

• Balaguer, Juan Ramon (Universidad de Murcia)
• Giorgi, Giacomo (Universidad de Murcia)
• Saura, Pablo (UPCT, IFT-UAM/CSIC)

 

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Accommodation.docx

Accommodation.odt

Map_Buses_and_Tram.pdf

map_campus.pdf

map_hotels.pdf

PosterEdelstein.pdf

Poster.pdf

Wednesday 11 January

08:30 → 08:50 Registration

08:50 → 09:00 Welcome

09:00 → 10:00 Invited Contribution

09:00 Microscopic origin of the entropy of black holes in general relativity

We present a construction in which the origin of black hole entropy gets clarified. We start by building an infinite family of geometric microstates for black holes in general relativity. This construction naively overcounts the Bekenstein-Hawking entropy. We then describe how wormholes in the Euclidean path integral for gravity cause these states to have exponentially small, but universal, overlaps. These overlaps recontextualize the Gibbons-Hawking thermal partition function. We finally show how these results imply that the microstates span a Hilbert space of log dimension equal to the Bekenstein-Hawking entropy.

Speaker: Magán, Javier (University of Pennsylvania)

IberianMicrostates.key

10:00 → 11:00 30' Contribution

10:00 On the thermodynamics of Kaluza-Klein black holes

We study the thermodynamics of Kaluza-Klein black holes from the lower-dimensional point of view in which they are solutions of gravity coupled to a scalar and a vector field and from higher-dimensional point of view in which they are pure gravity (vacuum) solutions and compare both points of view which, in particular, should lead to exactly the same zeroth and first laws.

Speaker: Ortin, Tomas (Institute for Theoretical Physics IFT-UAM/CSIC, Madrid)

On the thermodynamics of KK BHs.pdf

10:30 Flavored anisotropic black holes

We construct a black hole geometry dual to a (2+1)-dimensional defect in an ambient (3+1)-dimensional gauge theory at non-zero temperature and quark density. The geometry is a solution to the equations of motion of type IIB supergravity with brane sources, a low energy limit of an intersection of stacks of color D3-branes and flavor D5-branes. We consider the case in which the number of D5-branes is large and they can be homogeneously distributed along the directions orthogonal to the defect, creating in this way a multilayer structure. The quark density is generated by exciting a gauge field in the worldvolume of the dynamic brane sources. We study the thermodynamics of the anisotropic black hole and compute the energy density of the dual theory, as well as the pressures and speeds of sound along the directions parallel and orthogonal to the defect. We also calculate transport coefficients in the shear channel, quark-antiquark potentials, and the entanglement entropies for slab subregions. These analyses give us a good overview on how the degrees of freedom are spread, entangled, and behave in this unquenched system in the deconfining phase at strong coupling.

Speaker: Penin Ascariz, Jose Manuel (University of Helsinki)

iberian_murcia_josemanuelpenin.pdf

11:00 → 11:20 Coffee break

11:20 → 12:50 30' Contribution

11:20 Corrections to AdS_5 black hole thermodynamics from higher-derivative supergravity

I will discuss the results that have recently appeared in 2208.01007 [hep-th], where we study four-derivative corrections to five-dimensional minimal gauged supergravity and evaluate the on-shell action of the AdS_5​ black hole solution with two independent angular momenta and one electric charge at linear order in the corrections. After imposing supersymmetry, we are able to recast the action in terms of the supersymmetric chemical potentials and match the result obtained from the dual superconformal index on the second sheet. We then use the on-shell action to determine the corrections to the black hole thermodynamics, including those to the entropy and the charges. We then specialize to the supersymmetric and extremal case and find a simple expression for the microcanonical entropy. In particular, for the case with one independent angular momentum the corrections are entirely encoded in the dual superconformal anomaly coefficients. We corroborate our results for the black hole entropy constructing the corrected near-horizon solution and applying Wald's formula and also evaluating the Legendre transform of the supersymmetric on-shell action.

Speaker: Ruiperez, Alejandro (Università di Roma Tor Vergata)

20230112 IBERIAN STRINGS MURCIA.pdf

11:50 Trans-IR flows to black hole singularities

Probing the interior of a black hole using gauge/gravity duality remains an active area of research. In this talk, I will present one recent attempt to probe the black hole interior by analytically continuing traditional holographic RG flows beyond their IR-fixed point. Such "trans-IR" flows are a natural framework for describing physics inside of black holes. First, I will discuss the construction of a monotonic holographic a-function which counts degrees of freedom along the trans-IR direction. Then with this function, I will argue that the degrees of freedom "thin out" and vanish when flowing to a trans-IR endpoint, represented by a Kasner singularity. Finally, I will discuss the relationship between this 'a' function and well-studied quantum information probes in the language of trans-IR flows.

Speaker: Patra, Ayan Kumar (IFT-Madrid)

Trans IR flows to BH Singularity_Ayan_Patra.pdf

12:20 Electromagnetic generalized quasi-topological gravities in three dimensions

We present new families of three-dimensional gravities non-minimally coupled to a scalar field whose effective on-shell Lagrangian becomes a total derivative when evaluated in a static spherically symmetric ansatz for the metric and a magnetic-like solution for the scalar field. After integrating once, the resulting equations of motion are of second order at most. We show that these theories, dubbed Generalized quasitopological gravities, exist at every order in curvature. We also present their covariant expression and a recursive relation that allows to construct them at arbritrarily high order. After that, we focus on solutions to the quasitopological family. We check that they corresponds to multiparametric generalizations of the Bañados-Teitelboim-Zanelli black hole, describing a plethora of new analytic black holes and globally regular horizonless spacetimes. Interestingly, in some cases the black holes have no singularity at all, being completely regular.

Speaker: Moreno, Javier (Technion-Haifa U.)

Moreno - EGQT in 3D v2.pdf

12:50 → 13:05 15' Contribution

12:50 Stringy Black Holes with alpha prime corrections

I will review some recent results in the costruction of alpha prime corrections of some families of well known solutions of 10 dimensional heterotic string theory and I will comment on their thermodynamical properties. The families taken into account correspond to extremal (non)supersimmetric black holes, their non-extremal generalization and solutions describing multiple (non)supersymmetric extremal black holes in equilibrium. The talk is based on [2111.15579], [2112.12764] and [2210.01861].

Speaker: Zatti, Matteo (IFT UAM/CSIC)

IberianStringsZatti.pdf

13:05 → 15:00 Lunch

15:00 → 16:00 Invited Contribution

15:00 Symmetries of TTbar-deformed CFTs and their manifestations in holography

Speaker: Guica, Monica (Institut de Physique Théorique)

ttb_lst.pdf

16:00 → 16:30 30' Contribution

16:00 A universal feature of charged entanglement entropy

In a theory with global symmetries, one can define a notion of charged entanglement entropy, which is a function of the chemical potential conjugate to the charge contained in the entangling region. In this talk, I will show that for a general d(≥3)-dimensional CFT, the leading correction to the uncharged entanglement entropy across a spherical entangling surface is quadratic in the chemical potential, positive definite, and universally controlled by the coefficients of the correlators <JJ> and <TJJ>. This result is motivated by analytic holographic calculations for a special class of higher-curvature gravities in general dimensions as well as for free fields in d=4. A proof for general theories and dimensions follows from previously known universal identities involving the magnetic response of twist operators.

Speaker: Cano, Pablo A. (KU Leuven)

Cano.pdf

16:30 → 16:50 Coffee break

16:50 → 17:50 30' Contribution

16:50 Higher-derivative holography with a chemical potential

We carry out an extensive study of the holographic aspects of any-dimensional higher-derivative Einstein-Maxwell theories in a fully analytic and non-perturbative fashion. We achieve this by introducing the d-dimensional version of Electromagnetic Quasitopological gravities: higher-derivative theories of gravity and electromagnetism that propagate no additional degrees of freedom and that allow one to study charged black hole solutions analytically. These theories contain non-minimal couplings, that in the holographic context give rise to a modified <JJ> correlator as well as to a general <TJJ> structure whose coefficients we compute. We constrain the couplings of the theory by imposing CFT unitarity and positivity of energy (which we show to be equivalent to causality in the bulk) as well as positive-entropy bounds from the Weak Gravity Conjecture. We also obtain the charged Rényi entropies and we observe that the chemical potential always increases the amount of entanglement and that the usual properties of Rényi entropies are preserved if the physical constraints are met. Finally, we compute the scaling dimension and magnetic response of twist operators and we provide a holographic derivation of the universal relations between the expansion of these quantities and the coefficients of <JJ> and <TJJ>.

Speaker: Murcia, Ángel (Istituto Nazionale di Fisica Nucleare, Sezione di Padova)

IBStrings2023_Angel_Murciav2.pdf

17:20 Damping of Pseudo-Goldstone Fields from Schwinger-Keldysh Effective Field Theory

Approximate symmetries abound in Nature. If these symmetries are also spontaneously broken, the would-be Goldstone modes acquire a small mass, or inverse correlation length, and are referred to as pseudo-Goldstones. At nonzero temperature, the effects of dissipation can be captured by hydrodynamics at sufficiently long scales compared to the local equilibrium. In this talk we will explain how the framework of Schwinger-Keldysh effective actions for hydrodynamics allows us to show that the damping of pseudo-Goldstones is completely determined by their mass and diffusive transport coefficients. We will also discuss how we can use a simple holographic model in order to derive such Schwinger-Keldysh effective actions for the hydrodynamics of broken symmetries.

Speaker: Ziogas, Vaios (École Polytechnique)

Ziogas_Iberian Strings.pdf

17:50 → 18:50 15' Contribution

17:50 Holographic Floquet states in low dimensions

I'll discuss our recent work, in which we study holographically a strongly coupled (2+1)-dimensional gauge theory subject to an external rotating electric field, both at zero and non-zero temperature. The system is modelled holographically as a D3/D5 probe intersection, and we analyze the phase diagram. We find a conductive phase and an insulating phase, and we observe that the conductive phase extends down to vanishing external electric field at discrete values of the frequencies where vector meson Floquet condensates form. For all temperatures, at given intercalated frequencies, we find new dual states that we name Floquet suppression points, where the vacuum polarization vanishes even in the presence of an electric field. From the data we infer that these states exist both in the conductive and insulating phases. In the massless limit we find a linear and instantaneous conductivity law, recovering known general results in 2+1 dimensions. We also examine the photovoltaic AC and DC current as the response to an oscillating probe electric field and see that rising the temperature suppresses the photovoltaic Hall current. All the results obtained carry over qualitatively unaltered to the case of D3/D7.

Speaker: Berenguer Mimó, Martí (IGFAE, Universidade de Santiago de Compostela)

MartiBerenguer_IberianStrings2023v2.pdf

18:05 Holographic BCFT Spectra from Brane Mergers

Recently, boundary conformal field theories (BCFT) and their holographic duals have received renewed attention due to appearing in models of black hole evaporation. The holographic models involve dynamical end-of-the-world (EOW) branes that encode properties of the BCFT boundary in gravity. In the case of 3D gravity, simple EOW brane models are not able to describe excited states or boundary condition changing (BCC) operators of the dual 2D BCFT. In this talk, I show how to overcome these shortcomings by coupling the bulk theory to scalar fields and point-particles while at the same time allowing the branes to intersect non-smoothly. It turns out that BCC operators are exactly described by the intersecting brane configurations. I will also mention a new bra-ket wormhole saddle whose CFT interpretation seems to require ensemble averaging. Based on: 2209.11227

Speaker: Kastikainen, Jani (Université Paris Cité, APC laboratory)

Talk_Kastikainen_V3.pdf

18:20 An Outsider's Perspective on Information Recovery in de Sitter Space

Entanglement islands play a crucial role in our understanding of how Hawking radiation encodes information in a black hole, but their relevance in cosmological spacetimes is less clear. In this paper, we continue our investigation of information recovery in de Sitter space and construct a two-dimensional model of gravity containing a domain wall that interpolates between de Sitter space and Rindler space. The Rindler wedges introduce weakly-gravitating asymptotic regions from which de Sitter space can be probed, yielding an outside perspective of the cosmological horizon. In contrast to earlier works, backreaction effects are under control by considering a quantum state that only breaks the thermal equilibrium of the Bunch-Davies state for a finite time. This allows information to be decoded from the Gibbons-Hawking radiation in a controlled fashion.

Speaker: Mr Aguilar Gutierrez, Sergio Ernesto (KU Leuven)

Outsiders perspective.pdf

18:35 Analyticity of the wavefunction of the universe

In recent years there has been an increasing interest in the interplay between amplitudes and cosmological correlators, in particular in the use of amplitudes techniques to constrain cosmological correlators. In this talk, I will give an overview of the formalism of the wavefunction of the universe and how it relates to cosmological correlators. After this, I will review the success of the S-matrix programme in studying the analytic properties of the amplitude of scattering A(s,t) in a gapped theory. Among the many results, I will focus on the sum rules for Wilson coefficients, which relate the coefficients in an EFT expansion with an integral of the UV completion of the theory. To incorporate the sum rules to the wavefunction of the universe framework, we define off-shell wavefunction coefficients whose analytic structure is fixed by its tree-level diagrams. The resulting sum rules encapsulate a larger set of Wilson coefficients than those from amplitudes. Finally, I will address future research in the rich interplay between amplitudes and cosmology

Speaker: Agüí Salcedo, Santiago (University of Cambridge)

The_analytic_wavefunction__short_-3.pdf

Thursday 12 January

09:00 → 10:00 Invited Contribution

09:00 Quantum Gravity, Chaos and Statistical Physics

In this talk I will describe a picture which has emerged over the past few years regarding the statistical interpretation of semiclassical gravity and how this relates to wormholes, averaging and the so-called factorization puzzle.

Speaker: de Boer, Jan (University of Amsterdam)

murcia0123.pdf

10:00 → 11:00 30' Contribution

10:00 Conformal dualities from unoriented gauge theories

We study various orientifold projections of 4d N = 1 toric gauge theories. We obtain superconformal field theories that have the same central charge, anomalies and superconformal index, whereas they were different before the orientifold. Some of these projections are implemented by a novel type of orientifold without fixed loci, known as glide orientifold. We claim that these theories flow to the same conformal manifold, and they are connected by exactly marginal deformations.

Speaker: Riccioni, Fabio (INFN Roma La Sapienza)

TalkRiccioni.pdf

10:30 Leigh and Strassler Spindled

Spindles are two-dimensional orbifolds that are topologically two-spheres, but with conical deficit angles at the north and south poles. These compact spaces are interesting, because under certain circumstances they provide a novel way to preserve supersymmetry which is distinct from the familiar topological twist. This observation
opens the possibility to construct new classes of interacting superconformal field theories (SCFTs), by compactifying higher dimensional SCFTs on spindles. In this talk, I will introduce a new class of two-dimensional N=(0,2) SCFTs in their holographic limit. By
appealing to anomaly matching arguments I further provide evidence of their higher dimensional origin--a well known four-dimensional SCFT compactified on a spindle.

Speaker: Rosen, Christopher (CCTP, University of Crete)

IberianStrings23_ROSEN.pdf

11:00 → 11:20 Coffee break

11:20 → 12:50 30' Contribution

11:20 Towards a non-relativistic AdS/CFT duality

It is well-known that non-relativistic limits of a string theory modify its background geometry, which no longer remains Lorentzian. This opens a new window into non-AdS holography, for instance by taking a non-relativistic limit of the most studied and understood case, namely strings in AdS5xS5. Although its non-relativistic dual field theory has not been identified yet, in this talk we shall focus on the string side of the correspondence. We report on recent progress in non-relativistic strings in AdS5xS5, namely on classical solutions, semiclassical expansion and a Lax pair.

Speaker: Fontanella, Andrea (Perimeter Institute for Theoretical Physics)

FONTANELLA.pdf

11:50 A non-relativistic vivisection of 11-dimensional supergravity

Non-relativistic limits of string and M-theory offer a way to (in principle) explore non-relativistic quantum gravity. In this talk I will focus on the realisation of such a limit for 11-dimensional supergravity. Bosonically this results in a non-Lorentzian "membrane Newton-Cartan geometry" with the local tangent space split into three "longitudinal" and eight "transverse" directions, related by Galilean rather than Lorentzian symmetries. Consistency of the limit and its compatibility with local supersymmetry imposes additional constraints on this geometry, and reveals a surprising and intricate non-relativistic supergravity theory in a sense lurking within the (famously unique) relativistic theory. I will explain how this works, and discuss the relationship to the duality web of both relativistic and non-relativistic theories. Based on upcoming work with E. Bergshoeff, J. Lahnsteiner and J. Rosseel.

Speaker: Blair, Chris (IFT-UAM/CSIC)

Blair.pdf

12:20 Nonlinear automorphism of the conformal algebra in 2D and continuous \sqrt{T\bar{T}} deformations

It depends on a single real parameter and it can be regarded as a ``nonlinear $SO(1,1)$ automorphism.'' The map preserves the form of the momentum density and naturally induces a flow on the energy density by a marginal $\sqrt{T\bar{T}}$ deformation. In turn, the general solution of the corresponding flow equation of the deformed action can be analytically solved in closed form, recovering the nonlinear automorphism. The deformed CFT$_{2}$ can also be described through the original theory on a field-dependent curved metric whose lapse and shift functions are given by the variation of the deformed Hamiltonian with respect to the energy and momentum densities, respectively. The conformal symmetries of the deformed theories can then also be seen to arise from diffeomorphisms that fulfill suitably deformed conformal Killing equations. Besides, Cardy formula is shown to map to itself under the nonlinear automorphism. As a simple example, the deformation of $N$ free bosons is briefly addressed, making contact with recent related results and the dimensional reduction of the ModMax theory.

Speaker: Tempo Rangel, Jose David (Universidad Católica de Temuco (UCT))

IberianString2023Murcia-00.key

12:50 → 13:05 15' Contribution

12:50 On action and properties of 10D multiple D0-brane system

We present an action for the dynamical system of N nearly coincident multiple D0-branes and strings connecting these D0-branes (mD0 system) which is invariant under spacetime (type IIA target superspace) supersymmetry and the local worldline supersymmetry generalizing the kappa-symmetry of single D0-brane action (massive D=10 superparticle or Dirichlet superparticle). The action includes an arbitrary nonvanishing function M(H) of the relative motion Hamiltonian H. The 10D mD0 model with a particular form of M(H) can be obtained by dimensional reduction from the action of the D=11 multiple M-wave (mM0) system. This talk is based on Phys. Rev. D106 (2022) 066004 with Igor Bandos.

Speaker: De Miguel Sárraga, Unai (Department of Physics and EHU Quantum Center, University of the Basque Country UPV/EHU)

UnaiDMS_IBS_2023.pdf

13:05 → 15:00 Lunch

15:00 → 16:00 Invited Contribution

15:00 Swampland constraints from cobordisms

TBA

Speaker: Montero, Miguel (Harvard University)

iberian-strings.pdf

16:00 → 16:30 30' Contribution

16:00 Asymptotic Accelerated Expansion in String Theory?

In this talk I will address the question: Is there asymptotic accelerated expansion in string theory? First I will present a Swampland conjecture suggesting a negative answer. It has been tested in a particular asymptotic limit associated to weak string coupling and large volume in Type II string theory compactifications. To go beyond this lamppost, we consider different asymptotic limits of F-theory flux compactifications on Calabi-Yau fourfolds. I will discuss a couple of candidates that could feature asymptotic accelerated expansion once the Kähler moduli are stabilized. Based on arXiv:2209.11821 in collaboration with I. Ruiz and I. Valenzuela.

Speaker: Calderón-Infante, José (CERN)

Calderon-Infante.key

16:30 → 16:50 Coffee break

16:50 → 17:50 30' Contribution

16:50 T-duality building blocks in stringy corrections

T-duality has been shown to constrain the higher derivative corrections of string theory. We revisit the problem of understanding the T-duality constraints imposed on the alpha prime corrections using the language of a torsionful connection to construct O(d,d) invariant building blocks for general d-dimensional torus compactifications. This also suggests that there are in fact some hidden geometrical structures in string theory and use this to revisit the heterotic and bosonic ten-dimensional string action at order alpha prime.

Speaker: David, Marina (KU Leuven)

Marina_David_Slides.pdf

17:20 New sectors of string theory from supermembranes with discrete spectrum

In the talk I will comment on two new sectors of string theory that are related to two sectors of the Supermembrane theory with a purely discrete spectrum. We will see that from the sector of the compactified supermembrane with constant and quantized 3-form supergravity background and monodromy contained in $SL(2,Z)$, by double dimensional reduction, it is obtained a new type of (p,q) string in 9D with a reduced parabolic symmetry and with a new tension and a flux contribution. This string is associated with the supermembrane with parabolic monodromy. At low energies, it should correspond to the type II parabolic gauged supergravity in 9D. On the other hand, from the massive supermembrane, which corresponds to a supermembrane on a puntured Rieman surface when a particular double dimensional reduction is performed, it is possible to obtain a worldsheet description of a new type of N=2, IIA string in 10D. We will discuss its main properties and its relation with the conjectured massive type IIA string from Romans supergravity.

Speaker: García del Moral, María del Pilar (Universidad de la Rioja)

IberianstringsFrev 2023.pdf

17:50 → 18:20 30' Contribution

17:50 Local supersymmetry enhancement and the entropy of three-charge black holes

In string theory, black holes can be realised as bound states of branes and strings. The branes and the strings preserve a set of global supersymmetries, which imposes the geometry of the near-horizon region. However, there exists a whole moduli space of brane systems that preserve those same global supersymmetries, but whose number of local supersymmetries is enhanced. Such brane configuration should describe some microstates of the black hole; but how much of the black-hole entropy can these configurations account for? In this talk, I will first present this (new) formalism based on local supersymmetries that identifies the ingredients needed to describe the microstates of a supersymmetric black hole. Then, I will illustrate the local supersymmetry enhancement mechanism with the three-charge F1-NS5-P black hole and its U-dual, the M2-M5-P black hole. In Type IIA, the black-hole entropy is accounted by the fractionation, due to the presence of the five-branes, of the fundamental strings into many ‘little strings’ which act as independent momentum carriers. These microstates are the celebrated ‘’Dijkgraaf-Verlinde-Verlinde (DVV) microstates,’’ and have a description in M theory in terms of strips of M2 branes connecting pairs of parallel M5 branes. I will apply the supersymmetric enhancement mechanism to the DVV microstates, and show it gives rise to a new class of black-hole microstate solutions which preserve the rotational symmetry of the black-hole horizon. Finally, I will explain why one should expect their supergravity description to be horizonless, and thus, how our results point towards a change of strategy in the fuzzball programme in the endeavour of constructing horizonless black-hole microstates. Based on [arXiv:2211.14326] with I. Bena, S. Hampton, A. Houppe and D. Toulikas.

Speaker: Li, Yixuan (MPI Munich)

Yixuan Li - presentation.pdf

18:20 → 18:35 15' Contribution

18:20 On the running of gauge couplings in string theory

String theories naturally give rise to infinite towers of states whose degeneracies grow exponentially as functions of mass. These infinite towers of states are ultimately responsible for many of the finiteness properties for which string theory is famous. Recently, a framework was developed in which the effects of all of these states can be incorporated in a self-consistent way when calculating quantities relevant for low-energy phenomenology, such as the masses of the Higgs fields that arise in such theories. This formalism also gives rise to an "on-shell'' effective field theory description in which the final results are expressed in terms of contributions from only the on-shell, level-matched physical string states, and in which these quantities also exhibit an EFT-like "running'' as a function of an effective spacetime mass scale. In this talk I’ll discuss hot to apply this formalism to calculate the running of the gauge couplings within closed string theories. Unlike previous calculations in the literature, our calculation fully respects the underlying closed-string modular invariance and expresses many of the final results in terms of contributions from only the on-shell physical string states. We find, however, that the calculation of the gauge couplings differs in one deep way from the calculation of the Higgs mass: while the latter results depend on the supertraces over only the on-shell string states, the former results have a different modular structure which causes them to depend on supertraces over the off-shell string states as well. Taken together, our results yield the expected logarithmic running of the gauge couplings at certain energy scales. However, they also yield a number of intrinsically stringy behaviors that transcend what might be expected within an effective field theory approach.

Speaker: Nutricati, Luca Armando (Durham University)

Iberian Strings 23.pdf

20:15 → 22:15 Social Dinner

Friday 13 January

09:00 → 10:00 Invited Contribution

09:00 Differential Equations for Cosmological Correlators

I will review the “bootstrap” approach to compute primordial correlation functions in cosmology (which control the initial conditions for structure formation in the universe). This bootstrap relies on the existence of differential equations in terms of boundary momenta. I will describe a new method to efficiently characterize and (in some sense) explain the existence of these differential equations. The method is general—in fact, it is heavily inspired by technology used in loop computations in flat space---, but I will focus on cosmological correlation functions of a light scalar in power law FLRW cosmologies. It recasts the differential equation in terms of a new (somewhat magical) object, a flat connection in the boundary kinematic space. The mathematical theory of this flat connection is beautiful on its own right, and not fully developed yet. The physical information it carries — in particular, locality of the correlator — is encoded in its structure in a way that I don’t fully understand.

Speaker: Leite Pimentel, Guilherme (Scuola Normale Superiore)

10:00 → 11:00 30' Contribution

10:00 The correspondence between rotating black holes and fundamental strings

The correspondence between black holes and degenerate states of fundamental strings becomes puzzling when attempting to include rotation: At large enough spins, there exist degenerate string states that seemingly cannot be matched to any black hole. Conversely, there exist black holes with arbitrarily large spins that cannot correspond to any single-string state. I will discuss work (to appear) with Ceplak, Puhm and Tomasevic, where we address these problems.

Speaker: Emparan, Roberto (ICREA & ICC U Barcelona)

RotCorresp_IbStrings.pdf

10:30 Holographic duals to black hole evaporation

We describe the dynamical evaporation of a black hole through quantum Hawking emission in holographic form, namely, as the classical gravitational evolution of a black hole in an Anti-de Sitter braneworld. A bulk black hole whose horizon intersects the brane yields the classical bulk dual of a black hole coupled to quantum conformal fields. The evaporation of this black hole happens when the bulk horizon slides off the brane, making the horizon on the brane shrink. We use a large-D effective theory to solve the time evolution of the bulk Einstein equations. With this method, we study the dual dynamical evaporation of a variety of black holes interacting with radiation baths. We also obtain the dual of the collapse of holographic radiation to form a black hole on the brane. Finally, we discuss the evolution of the Page curve of the radiation in our evaporation setups, with entanglement islands appearing and then shrinking during the decreasing part of the curve.

Speaker: Tomasevic, Marija (CPHT, Ecole polytechnique)

the dual dynamics of quantum black holesfff.pdf

11:00 → 11:20 Coffee break

11:20 → 12:50 30' Contribution

11:20 Multipartite information in conformal field theories

The mutual information between two subsystems is a well-known information theoretic quantity which, contrary to other measures such as entanglement entropy, remains finite in the continuum limit of quantum field theories. It is possible to generalize it by considering a system made out of N distinct parts, in which case we compute the N-partite information shared by them. In this talk, we will provide some general results for the N-partite information between spatial subregions in the ground state of CFTs: generic behaviour at long distances, relation between bulk and boundary N-partite informations in holographic theories, and lattice computations for a free boson in 2+1 dimensions, which support the analytical results obtained.

Speaker: Vilar López, Alejandro (Université Libre de Bruxelles (ULB))

Multipartite16-9-split.pdf

11:50 Extended Thermodynamics on the brane

I will talk about extended thermodynamics in the braneworld scenario. I will discuss motivations, the holographic derivation and examples. In particular, I will illustrate the quantum BTZ black hole example.

Speaker: Frassino, Antonia Micol (ICC, University of Barcelona)

Frassino_iberian_strings_2023.pdf

12:20 Asymptotic symmetries at spatial infinity

The BMS (Bondi-van der Burg-Metzner-Sachs) group was shown long ago to be the group of asymptotic symmetries of gravity in asymptotically flat spacetime. This group naturally emerges at null infinity, however, analyses at spatial infinity did not exhibit any sign of the BMS group. This discrepancy was recently resolved by considering appropriate “parity twisted boundary conditions” at spatial infinity leading to a full agreement with the result at null infinity. This talk will briefly describe how the infinite dimensional BMS group appears at spatial infinity along with recent efforts in both its higher spacetime dimensions description and its elusive enhancement with superrotations.

Speaker: Matulich, Javier (IFT-UAM/CSIC)

Iberian_Strings_Matulich.PDF

12:50 → 13:05 15' Contribution

12:50 Higher-curvature Gravities from Braneworlds and the Holographic c-Theorem

We study the structure of the higher-curvature gravitational densities that are induced from holographic renormalization in AdSd+1. In a braneworld construction, such densities define a d-dimensional higher-curvature gravitational theory on the brane, which in turn is dual to a (d-1)-dimensional CFT living at its boundary. We show that this CFTd−1 satisfies a holographic c-theorem in general dimensions, since at each and every order the higher-curvature densities satisfy c-theorems on their own. We examine various other features of the holographically induced higher-curvature densities.

Speaker: Llorens, Quim (ICC U Barcelona)

QLlorens_IbStrings23.pdf

13:05 → 15:00 Lunch

15:00 → 16:00 Invited Contribution

15:00 de Sitter space and braneworld holography

Quantum backreaction in semi-classical gravity is a notoriously difficult task. In this talk, I will explain how braneworld holography can help us tackle this problem. I will review some basic properties of braneworld models with or without a cosmological constant, emphasizing various semi-classical properties of the solutions. As an application, I will consider the backreaction due to conformal matter in conical de Sitter space and show that it gives rise to quantum dS black holes in 3D, solutions that do not have a classical counterpart.

Speaker: Pedraza, Juan (IFT-CSIC/UAM)

dS-Branes-Pedraza.pdf

16:00 → 16:30 30' Contribution

16:00 Towards finite baryon density in confining solutions

Understanding the phase diagram of QCD at finite density and temperature remains one of the most prominent open problems in modern physics. In this talk, I will present a model in type IIA supergravity that describes holographically a QCD-like theory at strong coupling. I will show how the phase diagram at finite temperature and external magnetic field looks like. This turns out to be quite rich, both with first and second order confinement/deconfinement phase transitions and a critical point. Finally, I will explain how these results are leading us to find the first realization of finite baryon density in a top-down confining holographic model.

Speaker: Subils, Javier (Nordita)

Javier_Subils.pdf

16:30 → 16:50 Coffee break

16:50 → 17:50 30' Contribution

16:50 Unitarization of infinite range forces, resonances in gravitational scattering of gravitons: The graviball

We study graviton-graviton scattering in partial-wave amplitudes after unitarizing their Born terms. In order to apply S-matrix techniques, based on unitarity and analyticity, we introduce an S-matrix associated to this resummation that is free of infrared divergences. This is achieved by removing the diverging phase factor calculated by Weinberg that multiplies the S matrix, and that stems from the virtual infrared gravitons. A scalar graviton-graviton resonance with vacuum quantum numbers is obtained as a pole in the nonperturbative S-wave amplitude, which we call the graviball. Its resonant effects along the physical real-s axis may peak at values substantially lower than the UV cutoff squared of the theory. For some scenarios, this phenomenon could have phenomenological consequences at relatively low-energy scales, similarly to the σ resonance in QCD. To further illustrate this method we also consider Coulomb scattering, and compare with its known solution. References: 1.- D.Blas,J.Martín-Camalich,J.A.Oller, Phys.Lett.B827,136991(2022) 2.- D.Blas,J.Martín-Camalich,J.A.Oller,JHEP08,266(2022) 3.- J.A.Oller,arXiv:2207.08784[hep-th]

Speaker: Oller, José Antonio (Universidad de Murcia)

String.pdf

17:20 BMS flux algebra and loop corrections to soft graviton theorems

I will discuss recent developments in the characterisation of asymptotic states in asymptotically flat gravity, and the central role played by BMS fluxes in connection to soft graviton theorems. As a result of these new ideas, I will show that the subleading soft graviton theorem including loop effects is the Ward identity associated with superrotations symmetries. We will conclude that BMS symmetries are genuine symmetries of the gravitational S-matrix beyond the classical regime. Based on arXiv:2205.11477.

Speaker: Nguyen, Kévin (King's College London)

KevinNguyen_talk.pdf

17:50 → 18:20 30' Contribution

17:50 Non-invertible Symmetries and theories of class S

Non-invertible symmetries is a generalization of a conventional notion of symmetry, which includes symmetry transformations that do not obey the group law, and in particular fail to have the inverse. In this talk I will discuss the construction of such non-invertible symmetries in class S theories, obtained by compactifying 6d (2,0) superconformal field theory on a Riemann surface with no punctures. The simplest example in this family is N=4 SYM. After setting up the general framework, I will describe how such symmetries can be classified up to genus 5. I will also explain the imprints of non-invertible symmetries in the Symmetry TFT of the theories under discussion.

Speaker: Bashmakov, Vladimir (Uppsala University)

Iberian_Strings_2023_Bashmakov.pdf

18:20 → 18:35 15' Contribution

18:20 The fate of horizons under quantum corrections

In this paper, we study the physical effects of deforming the usual Einstein-Hilbert lagrangian with the Goroff-Sagnotti counterterm (the first which is nonvanishing on shell). The related facts that Schwarzschild’s spacetime is not a solution to the corresponding equations of motion and Birkhoff’s theorem is not valid anymore are analyzed and some consequences worked out.

Speaker: Velasco Aja, Eduardo (IFT-UAM/CSIC)

Iberian2023VelascoAja.pdf

20:00 → 21:00 Public Talk

20:00 La lencería del cosmos

¿Cuál es la naturaleza íntima del espacio y del tiempo? ¿Qué ocurre cuando se desgarra en agujeros negros como el gigante del centro de nuestra Vía Láctea? Así como la materia está hecha de átomos, ¿existen unidades fundamentales del espacio-tiempo?
En esta charla, el profesor Edelstein presentará argumentos que sugieren la posible existencia de una recóndita estructura en el Universo dada por minúsculas cuerdas sin espesor. Explicará a los asistentes las sorprendentes consecuencias que este íntimo encaje, la “lencería” del cosmos, ofrece a nuestra comprensión del Universo.

Speaker: Edelstein, Jose (IGFAE, Universidade de Santiago de Compostela)