IV GRASS-SYMBHOL Meeting

The 4th meeting of the members of the two coordinated AEI-funded research grants Gravity Supergravity and Superstrings (GRASS, Ref. PID2024-155685NB-C21) and Strings, Supersymmetry, Black Holes and Holography (SYMBHOL, Ref. PID2024-155685NB-C22 ) will take place the 11th, 12th and 13th of November 2025 in Toledo (Spain). The previous 3 editions took place in Cuenca (2022), Ávila (2023) and Segovia (2024).

The goal of this meeting is to increase the contact between the researchers of both grants, getting to know the members of the other grant and their research, creating opportunities for collaboration and the interchange of ideas and scientific knowledge, to give opportunities to the young researchers to give a scientific talk in a friendly environment as part of their training. Old members of the research grants and external collaborators are also invited to participate.

This is the first occasion in which we are going to publish the scientific program and the presentations of the talks for the benefit of all those interested.

LIST OF PARTICIPANTS

César Agón (UP Cartagena)
Romina Ballesteros (U de San Sebastián, Chile)
Igor Bandos (UPV/EHU, Bilbao)
Gabriele Barbagallo (IFT UAM/CSIC)
Raúl Belmonte Aix (U Murcia)
Eric Bergshoeff (U Groningen)
Federico Bonetti (U Murcia)
Pablo Bueno (U Barcelona)
Pablo Cano (U Murcia)
José Luis V. Cerdeira (IFT UAM/CSIC)
José Juan Fernández-Melgarejo
Giacomo Giorgi (U Murcia)
Adolfo Guarino (U Oviedo)
Javier Matulich (IFT UAM/CSIC)
Patrick Meessen (U Oviedo)
Javier Molina-Vilaplana (UP Cartagena)
Ángel Murcia (U Barcelona)
Tomás Ortín (IFT UAM/CSIC)
Luca Romano (U Murcia)
Pablo Saura (UP Cartagena)
Carlos Shahbazi (UNED)
Elena Paola Simón Félix (U Murcia)
Matteo Zatti (U Munich)

LIST OF TALKS

(With links to the presentations, after the meeting takes place)

Tuesday 11th

Federico Bonetti (U. Murcia), Title: SymTFTs for continuous symmetries, Abstract: Ideas and methods from topological field theory have come to the fore as useful tools to characterize global symmetries of quantum field theories and their implications. In particular, the symmetry topological field theory (SymTFT) is a flexible framework that has been successfully applied to various kinds of symmetries, including higher-form symmetries, higher-group
symmetries, non-invertible symmetries. The SymTFT is best understood for finite symmetries. After providing a brief review of the SymTFT formalism, I will discuss some recent developments in its application to continuous
symmetries.
Adolfo Guarino (U. Oviedo) Title: Type IIB uplift of pure N=4, D=4 gauged supergravity Abstract: I will show how pure N=4, D=4 gauged supergravity can be uplifted to a class of non-geometric backgrounds of type IIB supergravity known as S-folds. This provides an alternative to the M-theory uplift constructed by Cvetic, Lu and Pope 25 years ago.
Pablo Saura (UP Cartagena) Title: Twist Fields and Anomalies for non-Invertible Symmetries Abstract: In this talk I will introduce Symmetry Resolved Entanglement Entropy from the twist field approach. I will build twist fields for non-invertible symmetries in 2d Rational Conformal Field Theories and show their connection to anomalies. The anomaly, understood as the lack of scalar primaries in the twisted-symmetry.
Igor Bandos (UPV/EHU, Bilbao) Title: Quantum state spectrum and field theory of D0-brane Abstract: We quantize D0-brane, the simplest representative of the family of supersymmetric Dirichlet p-branes, in its spinor moving frame formulation and analyze its quantum state spectrum. Besides being a preparatory stage for quantization of the complete supersymmetric multiple D0-brane (mD0) model, which is presently known only in the frame of spinor moving frame formalism, this is interesting as its own: despite the covariant quantization of D=10 D0-brane was discussed before, its quantum state spectrum was not analyzed and its field theory, describing that, was not studied. We show that the quantum state vector of the D0-brane is described by an on-shell superfield that collects the fields of the massive counterpart of the linearized type IIA supergravity supermultiplet which can be obtained as massive Kaluza-Klein mode of the dimensional reduction of the eleven dimensional supergravity down to ten dimensions. In case of having time, we will also briefly discuss a spinor helicity formalism for D0-brane which can be used as one of the basic elements for developing type IIA string theory amplitude calculus based on multiparticle generalizations of the on-shell superfields. Based on: arXiv:2509.11324 [hep-th] with Unai Sarraga and Mirian Tsulaia.
Luca Romano (U. Murcia) Title: Higher-Order Newton-Cartan Gravity Abstract: We study the non-relativistic Newton-Cartan limit of higher-order gravity theories in arbitrary dimensions. We first study it at the level of the action by introducing an additional 1-form gauge field and coupling it appropriately to the gravity sector. We extend this procedure to any theory whose Lagrangian is a function of the Ricci scalar, quadratic Ricci tensor and quadratic Riemann tensor. We also study the limit of the equations of motion for two models, Einstein-Gauss-Bonnet gravity and quadratic Ricci scalar theory. We prove that, in the first case, it is possible to obtain the Poisson equation by introducing a scalar field and imposing an appropriate constraint. In the latter case, we show that it is possible to get the Poisson equation from the limit of the equations of motion as long as the on-shell constraint used in the two-derivative theory is supplemented with a further condition. We give the expressions of the two higher-order corrected Poisson equations in terms of curvatures of Newton-Cartan geometry. In both cases, we derive the full set of non-relativistic equations and study their boost transformations. The two sets of equations of motion define zero-torsion Gauss-Bonnet Newton-Cartan gravity and zero-torsion quadratic Ricci scalar Newton-Cartan gravity.
César Agón (UP Cartagena) Title: Holographic Renyi entropy and Euclidean fluids Abstract: In this talk I will revisit the holographic prescription for refined Rényi entropies in the n→0 limit. In this regime, the reduced state behaves like a CFT fluid in local equilibrium, subject to vortex-like boundary conditions near the entangling surface. Using this intuition, we construct a dual bulk ansatz that solves Einstein’s equations with a cosmic brane, at leading order in the small n expansion, consistent with Dong’s proposal. The conical bulk ingularity naturally appears as the bulk continuation of the boundary fluid vortices.
Ángel Murcia (U. Barcelona) Title: Novel duality-invariant theories of electrodynamics Abstract: We identify new families of duality-invariant theories of electrodynamics. We achieve this in two different ways. On the one hand, we present an algorithm to construct a one-parameter family of exactly duality-invariant theories from a single seed duality-invariant theory. If the seed theory is causal, the theories constructed from this method will also be causal when the parameter is non-negative. On the other hand, we find two additional novel families of duality-invariant theories which include a nonzero term independent of the electromagnetic field. The first of them generalizes Bialynicki-Birula electrodynamics, while the second family of theories features a well-defined Maxwell limit as the term independent of the gauge field strength is sent to zero.
Elena P. Simon (U. Murcia) Title: Abstract:

Wednesday 12th

Javier Molina-Vilaplana (UP Cartagena) Title: Quantum Channels, Jones Index and Entropic Signatures of Symmetry Breaking of Non-Invertible Symmetries Abstract: In this talk, I present an algebraic and information–theoretic framework to characterize symmetry breaking of generalized, non-invertible symmetries in two spatial dimensions. The reduction of symmetry is modeled within the subfactor theory, where condensable Frobenius algebras play the role of subgroups in the categorical setting. This perspective naturally connects to the description of anyon condensation in topological phases of matter. Central to our approach are coarse-graining maps, or conditional expectations, which act as quantum channels projecting observables from a phase with higher symmetry onto one where the symmetry is partially or completely broken by condensation. By employing relative entropy as an entropic order parameter, we quantify the information loss induced by condensation and establish a universal bound governed by the Jones index, equal to the quantum dimension of the condensate. We illustrate the framework through explicit examples and show how dualities give rise to equivalence classes of condensation patterns. Our results forge new links between operator algebras, tensor category theory, and quantum information in the study of generalized symmetries.
Carlos Shahbazi (UNED) Title: The categorical symmetriesof the supergravity b-field Abstract: I will give a pedagogical introduction to bosonic NS supergravity as a higher gauge theory
Giacomo Giorgi (U Murcia) Title: Abstract:
Eric Bergshoeff (U Groningen) Title: An Introduction to Aristotelian Physics Abstract: In this talk I will discuss physical systems that are invariant under spacetime translations and spatial rotations but not under boost transformations. I will discuss the gauge theory of these Aristotelian symmetries and a conformal program that can be used to construct Aristotelian invariant actions. In particular, I will discuss the example of the so-called fractons.
Pablo Bueno (U Barcelona) Title: Regular black holes frompure gravity: lessons andperspectives Abstract: Recently, we have shown that regular black holes arise as the unique spherically symmetric solutions of a broad class of gravitational theories consisting of Einstein gravity supplemented by infinite towers of higher-curvature corrections. Within these models, such black holes form dynamically as a byproduct of the gravitational collapse of ordinary matter. In this talk, I will review the main results and lessons learned from this framework, and discuss new directions, including: the four-dimensional version of the models, the interplay between matter couplings and regularity, the generality of Birkhoff’s theorem among higher-curvature theories, the fate of the inner horizon, and the outcome of the evaporation process.
Matteo Zatti (U Munich) Title: Insights on Non-Perturbative Corrections to Extremal Black Holes Abstract: We revisit and study quantum corrections to the supersymmetric entropy of BPS black holes in 4d N=2 supergravity, which can be obtained from Type IIA string theory compactified on a Calabi–Yau threefold. Macroscopically, these corrections arise from an infinite series of higher-derivative F-terms. They result from integrating out the tower of light D0-branes in the large volume patch. We analyze the most general black hole configuration with D0–D2–D4–D6 charges and find that this setup
can receive non-perturbative corrections. We interpret these corrections as arising from virtual particle pair production. We characterize the quantum effects by providing both a semi-classical description and a precise one-loop evaluation. We show that, despite the presence of non-trivial corrections, the stability of the system remains intact. As a byproduct, we uncover a correspondence among virtual pair production, classical confinement in the black hole throat and non-perturbative corrections to the Wald entropy.
Javier Matulich (IFT UAM/CSIC) Title: Gravity as a Deep Neural Network Abstract: Artificial Intelligence (AI) has achieved remarkable success in modeling complex systems across science and technology. At the heart of these advances are deep neural networks, inspired by the structure of the human brain and capable of learning intricate patterns from data. In recent years, these tools have begun to spark a paradigm shift in fundamental physics, opening the door to new ways of probing long-standing theoretical challenges. Among the fundamental interactions, gravity remains the least understood, with Einstein’s General Relativity working extremely well at macroscopic scales but failing to reconcile with Quantum Mechanics at the microscopic level. This talk explores the possibility of treating gravity itself as a deep neural network. By training physics-informed architectures on data from increasingly complex gravitational phenomena, one can encode physically meaningful features and gain new insights into gravitational interaction.
José Luis V. Cerdeira (IFT UAM/CSIC) Title: On-shell Lagrangians as total derivatives: general algorithm and some applications Abstract: Lagrangians which are total derivatives give trivial equations of motion. Nonetheless, when evaluated on-shell, non-trivial Lagrangians can be typically written as total derivatives. We prove that a Lagrangian which transforms homogeneusly under a global rescaling of the fields is a total derivative when evaluated on-shell and give a simple algorithm to compute it. Furthermore, we show that if one promotes the coupling constants to fields, all Lagrangians can be written as total derivatives. We will review some examples and show how this result can be applied to the construction of generalized Komar charges and to the Euclidean path integral.

Thursday 13th

José Juan Fernández-Melgarejo (U Murcia) Title: Abstract:
Romina Ballesteros (U de San Sebastián, Chile) Title: Non-closed scalar charge in 4-dimensional Einstein-scalar-Gauss-Bonnet blackholes Abstract: We define scalar charges for stationary, asymptotically flat black holes in 4-dimensional Einstein-scalar-Gauss-Bonnet gravity with a general scalar coupling function. Contracting the scalar field equation of motion with the horizon generator k yields a non-closed-form scalar charge, revealing a bulk contribution encoded in a 3–form, which measures the obstruction to its closedness. In the presence of shift-symmetry, this obstruction vanishes and the 2–form scalar charge satisfies a Gauss law, depending solely on boundary data. Geometrically, this reproduces known topological results in the shift-symmetric limit. This framework allows us to analyze the role of the non-closed scalar charges in black hole thermodynamics through the Smarr formula for more general couplings and provide a covariant, charge-based interpretation of the spontaneous scalarization mechanism, showing how the behavior of the scalar charge and the bulk term capture the instability of scalar-free black holes and the emergence of scalar hair. Our results offer a unified geometric understanding of the role of scalar charges and the mechanism of spontaneous
Gabriele Barbagallo (IFT UAM/CSIC) Title: Higher-form symmetries and generalized Komar charge in KK theory of gravity Abstract: In this talk I will present the construction of a generalized Komar charge for 5-D pure gravity with Kaluza–Klein (KK) boundary conditions that reproduces the 4-D mass. By exploiting the freedom to build conserved charges as linear combinations of other conserved charges, together with the well known higher-form symmetry of GR with KK boundary conditions, it is possible to build a Komar charge whose integral at spatial infinity for the timelike Killing vector generating time translations reproduces the physical 4D mass while removing the contribution of the 4-D KK scalar charge. I will conclude the talk by discussing how this construction can be extended to more complex situations, such as 5-D minimal supergravity.
Pablo Cano (U Murcia) Title: Amplification of new physics in the quasinormal mode spectrum, of highly-rotating black holes Abstract: The computation of quasinormal modes of rotating black holes in modified theories of gravity has been recently made possible thanks to the development of new techniques, like a modified Teukolsky equation and spectral methods. However, no method so far has been able to peek into the highly rotating regime — close to extremality. In this talk, I will consider a newly identified higher-curvature modification of GR that preserves the isospectrality of quasinormal modes in the eikonal limit. In this theory, eikonal perturbations can be described in terms of an effective scalar equation, and solving it we will obtain the corrections to the eikonal Kerr quasinormal modes for arbitrary rotation. For moderate rotation, we check that the eikonal computation gives a good approximation to the exact QNMs obtained from the modified Teukolsky equation, even for low harmonics. For high rotation, we discover that the corrections to GR become much larger and can lead to dramatic effects. Our results suggest that the observation of the ringdown of a highly rotating black hole would be a “golden event” to search.