Instituto de Física Teórica

Seminar: Constraining Muon decay parameters from CEvNS measurements at Spallation Sources
2025-11-27 15:00 - 16:00 (Europe/Madrid)
Speaker: Suraj Prakash, IFIC (Valencia)

Venue&Time: Red Room / 3:00 PM
Abstract: The talk will present a study of the sensitivity of COHERENT-like experiments to non-standard neutrino interactions within the vWEFT framework, i.e. low-energy EFT with additional right-handed Dirac neutrinos. Our analysis incorporates, for the first time, flavor-general New Physics effects in both neutrino production (from pion and muon decays) and neutrino detection, through Coherent Elastic Neutrino-Nucleus Scattering (CEvNS). As a special case, we will highlight how CEvNS data provide an alternative probe for muon decay parameters, for neutrino experiments where muon decay is a source of neutrinos. We will further illustrate how the results can be conveniently formulated in compact form and the ease with which they can be implemented in existing or future analyses using effective nuclear charges. Finally, We will discuss numerical results based on current COHERENT data, and also present estimates for the sensitivity of future measurements.

PhD dissertation: 'Shedding light on extended scalar sectors'
2025-11-28 12:00 - 14:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
By Víctor Enguita
Venue & Time: Red Room / 12:00
Abstract:
The Standard Model has a number of traits which are surprising from the theoretical perspective and may hint the presence of some underlying hidden structure beyond the SM. In this thesis, we explored some of the open problems which materialize from those traits and could be solved by the presence of an extended scalar sector. First, we considered axion-like particles (ALPs) using an Effective Field Theory (EFT) approach and imposed improved limits on their CP-odd couplings to fermions. The remainder of the thesis was devoted to the Electroweak hierarchy problem (EWHP). We presented two original works which follow two different guiding principles, one traditional and the other rather innovative: symmetry and near-critical dynamics. The first among these works presents non-abelian discrete symmetries as able to suppress large radiative corrections and stabilize the masses of scalar particles. In the second contribution, we argue that the small observed mass of the Higgs could be a trademark of the near-criticality of the Higgs sector, backed by the observation that every parameter in the Higgs potential seems in fact to also be near-critical. We explore the consequences of this fact using the so-called “Higgs metastability bound” in the case of a concrete model—the low-scale Majoron model—and demonstrate that this justification of the mass of the Higgs implies new experimental signals in future experiments and in particular, in the future colliders. We argue that this conclusion is actually more general and should apply to wider contexts than the concrete model analysed.
Supervisors: Belén Gavela & José Miguel No

Seminar: Quantum simulation of lattice gauge theories with Rydberg atom arrays
2025-12-01 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Daniel González Cuadra (IFT)
Venue&Time: Red Room / 15:00
Abstract: Lattice gauge theories (LGTs) describe a broad range of phenomena in condensed matter and particle physics. A prominent example is confinement, responsible for bounding quarks inside hadrons such as protons or neutrons. When quark-antiquark pairs are separated, the energy stored in the string of gluon fields connecting them grows linearly with their distance, until there is enough energy to create new pairs from the vacuum and break the string. While such phenomena are ubiquitous in LGTs, simulating the resulting dynamics is a challenging task. In this talk, I will report the observation of string breaking in synthetic quantum matter using a programmable quantum simulator based on neutral atom arrays [Nature 642, 321–326 (2025)]. I will first show how a (2+1)D LGT with dynamical matter can be efficiently implemented when the atoms are placed on a Kagome geometry, with a local U(1) symmetry emerging from the Rydberg blockade, while long-range Rydberg interactions naturally give rise to a linear confining potential between pairs of charges. In the experiment, we probe string breaking in equilibrium by adiabatically preparing the ground state of the atom array in the presence of defects, distinguishing regions within the confined phase dominated by fluctuating strings or by broken string configurations. Finally, by harnessing local control over the atomic detuning, we quench string states and observe string breaking dynamics exhibiting a many-body resonance phenomenon. As an outlook, I will present a roadmap to further explore phenomena in high-energy physics using programmable quantum simulators.

Holo Club: 'Complexity equals anything for multi-horizon black holes'
2025-12-02 11:30 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Hong-Yue Jiang (Lanzhou University)
Venue&Time: 11:30 / Gray Room 3
Abstract: We investigate the “complexity equals anything” proposal with codimension-one and codimension-zero gravitational observables for multi-horizon black holes, using the Bardeen-AdS class black hole as an example. In particular, we compare the results with the “complexity equals volume” (CV) proposal and find that the generalized volume complexitiy enables the probing of a more complete black hole interior, that is, all spacetime regions where the blackening factor $f(r)<0$. This is the advantage brought by the flexibility of this holographic complexity conjecture. In addition, we compute the codimension-zero gravitational observables derived from various geometric quantities and show that these constructions can effectively differentiate the distinct interior regions of the black hole.

Cosmology Journal Club
2025-12-02 14:00 - 15:00, 2026-01-20 14:00 - 15:00 | Discussion room 5th floor, C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, Madrid, 28049, Spain
Every Tuesday at 2:00 PM in the discussion room on the 5th floor.
Join the IFT cosmology/gravity journal club at benty-fields.com to vote for papers and volunteer to present them.

GRASS Seminar: 'Electric-magnetic duality of dyonic Kerr-Newman-NUT-AdS spacetimes'
2025-12-02 15:00 - 16:00
GRASS (GRAvity, Supergravity & Superstrings) Seminar
Speaker: Cristóbal Andrés Corral (Universidad Adolfo Ibáñez, Chle)
Venue & Time: Red Room / 15:00
Abstract: We discuss the (anti-)self-duality conditions under which the electric and magnetic parts of the conserved charges of the dyonic Kerr-Newman-NUT-AdS solution become equivalent. Within a holographic framework, the stress tensor and the boundary Cotton tensor are computed from the electric/magnetic content of the Weyl tensor. The holographic stress tensor/Cotton tensor duality is recovered along the (anti-)self-dual curve in parameter space. We show that the latter not only implies a duality relation for the mass but also for the angular momentum. The partition function is computed to first order in the saddle-point approximation and a BPS bound is obtained. The ground state of the theory is enlarged to all the (anti-)self-dual configurations when the SO(4) and U(1) Pontryagin densities are introduced. We demonstrate this at the level of the action and variations thereof.

Pheno Journal Club
2025-12-02 15:00 - 16:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Every Tuesday at 15:00 in Grey Room 3.

Quantum Information Journal Club: 'Programming quantum matter made with light and atoms'
2025-12-03 11:30 - 12:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Cristian Tabares

Venue & Time: 11:30 / Gray Room 3

Abstract: Current experimental quantum devices do not yet meet the requirements for building fault-tolerant quantum computers, but they can still be used to address many-body problems as analogue quantum simulators. Furthermore, recent experimental advances [1-4] are enabling these simulators to operate in a programmable manner [5], where their dynamics can be used as resources to generate a set of (non-universal) quantum gates. These controllable systems are able to generate highly entangled states, but a natural question is how to use these resources for quantum simulation purposes.

In this seminar we will discuss two different approaches. The first one will be based on state preparation, demonstrating how a classical device can be used to assist the analogue quantum simulator in the task of many-body state preparation [6,7] with variational algorithms. We will focus on fermionic atoms in optical lattices [8], constructing for ground-state preparation of local and extended Fermi-Hubbard models that show considerable improvements with respect to equivalent adiabatic methods. Then, in the second part of the talk, we will introduce an algorithm specifically tailored for analog quantum simulators to accurately recover their ground state properties [9]. Using only global time evolution under a target Hamiltonian, our algorithm avoids the need for local control that is typically required in conventional quantum phase estimation.

These results provide programmable quantum simulators with a new set of tools that further leverage their current capabilities. Overall, our work opens new avenues for analog simulators to make a wider and more efficient exploration of their relevant many-body Hilbert space.

[1] X. Zhang et al., Science 379, 278-283 (2023).
[2] C. Kokail et al., Nature 569, 355–360 (2019).
[3] S. Ebadi et al., Nature 595, 227–232 (2021).
[4] D. Bourgund et al., Nature 637, 57–62 (2025).
[5] A. J. Daley et al., Nature 607, 667–676 (2022).
[6] C. Tabares, A. Muñoz de las Heras, L. Tagliacozzo, D. Porras, and A. González-Tudela, Phys. Rev. Lett. 131, 073602 (2023).
[7] A. Muñoz de las Heras, C. Tabares, J. Schneider, L. Tagliacozzo, D. Porras, and A. González-Tudela., Phys. Rev. Research 6, 013299 (2024).
[8] C. Tabares, C. Kokail, P. Zoller, D. González-Cuadra and A. González-Tudela, PRX Quantum 6, 030356 (2025).
[9] C. Tabares, D. S. Wild, J. I. Cirac, P. Zoller, A. Gonzalez-Tudela, and D. González-Cuadra, arXiv:2511.04434 (2025).

SPS Journal Club: 'On the K-point in moduli space'
2025-12-04 12:00 - 13:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Alessandra Grieco (IFT)

Venue & Time: Red Room / 12:00

Abstract: We study a class of infinite-distance loci, referred to as K-points, in one-parameter complex-structure moduli spaces of type IIB string theory compactified on Calabi-Yau manifolds. We show that around K-points the effective four-dimensional supergravity exhibits certain unusual properties. The two most prominent being that the leading order dependence of the prepotential on the gauge couplings is non-perturbative and that the leading gauge kinetic terms in the action vanish when evaluated on an anti self-dual graviphoton background. These properties are shared with the conifold locus in moduli space, rather than the large complex-structure locus. The conifold locus is well-known to arise from integrating out a charged BPS state, and so the similarities suggest that the K-point also arises from integrating out a BPS state. We develop such an interpretation, finding that it corresponds to a BPS state which is extremely light, whose mass in Planck units is doubly-exponentially small in the distance to the K-point. The state behaves as if it had complex charges, or as if it couples to the self-dual and anti self-dual parts of the graviphoton differently. Assuming such an integrating-out scenario is indeed the correct physics for the K-point, we discuss the implications for our understanding of infinite distances in moduli space and for the Swampland Distance Conjecture.

Seminar: 'The Tolerable Inhomogeneity of the Baryon Asymmetry'
2025-12-04 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Stefan Stelzl from EPFL, Lausanne

Venue & Time: Red Room / 15:00

Abstract:

In this talk I present the implications of precision measurements of light element abundances in concordance with the Cosmic Microwave Background for scenarios of physics beyond the Standard Model that generate large inhomogeneities in the baryon-to-photon ratio. We show that precision Big Bang Nucleosynthesis (BBN) imposes strong constraints on any mechanism that produces large scale inhomogeneities at temperatures of the order or below a TeV. In particular, we find that inhomogeneities of the order of at comoving length scales larger than the comoving horizon at the temperature of are in conflict with the measured light element abundances. I then briefly highlight the phenomenological consequences thereof.

Old Journal Club: 'Field Theories with Superconductor Solutions'
2025-12-04 17:00 - 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Lorenzo Paoloni (IFT) will present :“Field Theories with Superconductor Solutions”, Nuovo Cim. 19 (1961) 154–164 de J. Goldstone.
Venue & Time: Blue Room / 17:00

Abstract: The conditions for the existence of non-perturbative type « superconductor » solutions of field theories are examined. A non-covariant canonical transformation method is used to find such solutions for a theory of a fermion interacting with a pseudoscalar boson. A covariant renormalisable method using Feynman integrals is then given. A « superconductor » solution is found whenever in the normal perturbative-type solution the boson mass squared is negative and the coupling constants satisfy certain inequalities. The symmetry properties of such solutions are examined with the aid of a simple model of self-interacting boson fields. The solutions have lower symmetry than the Lagrangian, and contain mass zero bosons.
More info: https://inspirehep.net/literature/12289

31st Xmas Workshop
2025-12-09 09:30 - 2025-12-11 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
From December 9th to December 11th 2025 we will celebrate the XXXI edition of our annual Christmas Workshop at the Instituto de Física Teórica (IFT) UAM-CSIC.
Leading experts will meet at the IFT to discuss recent developments in (astro) particle physics, phenomenology, cosmology, string theory, and quantum information.
More info.
Organizers:

Alejandro Bermudez
David Cerdeño
Gregorio Herdoíza
Miguel Montero
Pilar Coloma
Sven Heinemeyer
Yashar Akrami

Confirmed speakers:

Massimo Bianchi (Rome)
Diego Blas (IFAE)
Rebecca Gozzini (IFIC)
Aram Harrow (MIT)
Yolanda Lozano (U Oviedo)
Gonzalo Palma (Chile U.)
Ryan Plestid (CERN)
Carsten Urbach (U. Bonn)
Alexander Westphal DESY)
Giulia Zanderighi (MPI Munich)

posterIFTXmas25.pdf

Joint Colloquium IFT + ICMAT: 'Geometry of gauge theories in two dimensions'
2025-12-12 09:30 - 14:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Joint ICMAT-IFT Colloquium
After the colloquium, the traditional “Farewell to the Year” party will take place in the CFTMAT cafeteria.
Speaker: Oscar García-Prada (ICMAT-CSIC)
Date: Friday, 12 December 2025 – 12:00
Place: Blue Room
Abstract:
I will describe several geometric aspects of different gauge theories on Riemann surfaces that originate in four-dimensional Yang–Mills theories. A common theme is the appearance of various types of Higgs fields. I will provide some basic mathematical and historical background.

Seminar: 'Active Galactic Nuclei as Laboratories for Fundamental Physics'
2025-12-15 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Gonzalo Herrera (MIT & Harvard)
Venue & Time: Red Room / 15:00

Abstract: The vicinity of supermassive black holes at the center of Galaxies represents one of the most extreme environments in the Universe. In Active Galactic Nuclei (AGN), intense gravitational fields, relativistic particle acceleration, strong magnetic fields, and dense ambient gas and radiation coexist in conditions unmatched by other astrophysical sources or Earth-based laboratories. Recent high-energy neutrino observations from the IceCube collaboration and their electromagnetic counterparts from AGN have revolutionized the field of multi-messenger astronomy, providing the first direct window into the hadronic and leptonic processes operating at these cosmic accelerators, and opening new opportunities to test fundamental physics at energies and densities beyond terrestrial reach.
Here I will discuss how these environments can be exploited as laboratories for fundamental physics. I will first focus on dark matter–Standard Model interactions, showing how dark matter scattering with cosmic rays, neutrinos and gamma-rays can can lead to observable signatures on Earth. Second, I will consider other exotic phenomena that may occur independently on the dark matter background in these environments, such as photon-axion-like particle oscillations and microscopic black hole production from cosmic-ray collisions. Finally, I will conclude by showing how AGN can boost the cosmic neutrino background to higher energies via Standard Model processes, giving us a viable and promising pathway to detect the oldest particles in the Universe.

Pheno Journal Club: 'How large can lepton mixing be?'
2025-12-16 15:00 - 16:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Sergio Rodríguez Benítez (IFT)
Venue & Time: Grey Room 3 / 15:00
Abstract: We show that, contrary to common expectations, the observed charged leptons can have a substantial mixing with new heavier fermions, at the level of 20%. This can happen, in the language of effective theories, when the effect of mixing with heavier fermions vanishes at tree level in operators of mass-dimension 6 (or it is suppressed by the small charged lepton masses), a cancellation that can be naturally ensured by symmetries. Using a model that realizes this scenario we consider all current direct and indirect constraints and show that experimental constraints on the mixing are so mild that, given the current direct limit on the mass of the heavy fermions, theoretical considerations become the leading current constraints on the mixing. We also estimate the sensitivity to the mixing at future experiments, including the high-luminosity phase of the LHC and, most notably, the FCCee, and FCC-hh. We find a pattern in which the reach of direct searches in hadron machines makes theoretical considerations lead the limits while the precision of lepton machines can beat these theoretical considerations. We find that the FCC can finally reach per milleprecision in the mixing squared of the charged leptons.

GRASS Seminar: 'Axions, Three-Forms, and M-Theory'
2026-01-14 15:00 - 17:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Gravity, Supergravity and Superstrings (GRASS) Seminar
Speaker: Ziqi Yan (Niels Bohr Institute, Denmark)
Venue & Time: Red Room / 15:00
Abstract: Scalar fields with masses protected by global shift symmetries, commonly referred to as axions, are abundantly used in effective field theories in cosmology and particle physics. I will discuss a (4+1) dimensional braneworld construction for axion-like particles, where a 3-brane is coupled to a flux in the fifth dimension orthogonal to the brane, and its uplift to M-theory. From the (3+1)-dimensional perspective, this construction generates a mass for the axion and matches previously known proposals based on the coupling between the axion and a three-form gauge field.

SPS Journal Club: 'Exotic Branes and Symmetries of String Theory'
2026-01-15 12:00 - 13:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Andriana Makridou (IFT)
Venue & Time: Red Room / 12:00
Abstract: Are duality transformations symmetries of string theory? For AdS space-time the answer is
no for generic asymptotic values of the moduli, since the duality symmetry is broken explicitly
in the dual conformal field theory. In contrast, in string theory in flat space-time, monodromy
around codimension two exotic branes show that duality transformations are spontaneously
broken discrete gauge symmetries with observable consequences, provided macroscopic loops
of these branes are not hidden behind an event horizon. We discuss how this can be achieved
and how the situation in flat space-time differs from that in AdS space-time. We also discuss
observability of codimension two non-BPS branes and codimension one BPS and non-BPS
branes. Based on [2512.19068].

Pheno Journal Club: 'Bubble velocities in local equilibrium from a pseudopotential'
2026-01-15 12:00 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Eric Madge, IFT
Venue&Time: 12:00 / Grey room 3
Abstract: We present a new method to estimate terminal bubble velocities during first-order phase transitions in a plasma in local equilibrium. The method relies on calculating the extrema of a modified potential function for the scalar field undergoing the transition. The shape of this function, which we refer to as the “pseudopotential”, changes with the wall velocity, and if the dependence of the fluid temperature on scalar gradients is weak—which is confirmed to hold with high accuracy in concrete examples—the difference in pseudopotential between two appropriate extrema gives the net outward pressure acting on the bubble wall. It then follows that the correct terminal bubble velocities are those that lead to degenerate minima in the pseudopotential. This allows to compute bubble velocities without having to solve the equation of motion of the scalar field, and in contrast to other methods this can be done without relying on simplified equations of state for the plasma or without choosing a specific ansatz for the scalar field profile. We illustrate the method in a singlet extension of the Standard Model, computing the net outward pressure as a function of the wall velocity. We confirm the dip in outward pressure found in the literature for hybrid bubbles, which implies that stationary deflagrations are stable, while their detonation counterparts are unstable

Seminar: 'Dark Sector Karaoke: A 3D EFT for a Pitch-Perfect Phase Transition'
2026-01-15 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Cristina Puchades Ibáñez (University of Mainz)
Venue & Time: Red Room / 15:00
Abstract: We explore the dynamics of cosmological phase transitions in a dark sector model featuring a dark photon associated with a U(1)D gauge symmetry and radiative symmetry breaking. Our analysis focuses on different approaches to construct the effective potential: the high-temperature approximation, a full numerical evaluation of the thermal integrals, and a dimensionally reduced 3D effective theory built with DRalgo, at both leading and next-to-leading order. We as well explore the effect of including the running of the parameters in order to respect the hiercarchy scales. We investigate how these methods impact the characterization of the phase transition, particularly in the supercooled regime. Our results show the importance of method choice when predicting observable signatures, and establish a benchmark for future studies of first-order phase transitions in models with weakly coupled dark sectors.

SPS Journal Club: 'K-Points and Type IIB/Heterotic Duality with NS5-Branes'
2026-01-22 12:00 - 13:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Lorenzo Paoloni (IFT)
Venue & Time: Red Room / 12:00
Abstract: We revisit type II_0 limits in the vector multiplet moduli space of compactifications of Type IIB string theory on Calabi-Yau threefolds. These limits are special because they cannot be described using mirror symmetry. While we showed in previous work that the gravitational duality frame emerging in such limits corresponds to a weakly coupled heterotic string compactified on K3 times a string-sized torus, our focus here is on the additional field theory sectors that decouple from gravity in these asymptotic regimes. Concretely, we argue that, in the dual heterotic description, these field theory sectors correspond to spacetime-filling NS5-branes wrapping the heterotic torus. The existence of such non-perturbative field theory sectors manifests itself in an exponential dependence of the prepotential on the heterotic dilaton at leading order. Applied to K-point limits in one-parameter moduli spaces, our results imply that these limits are in perfect agreement with the Distance and Emergent String Conjectures. More precisely, the light tower of states predicted by the Distance Conjecture arises from excitations of a weakly coupled heterotic string compactified to four dimensions on a background containing spacetime-filling NS5-branes.

Pheno Journal Club
2026-01-22 12:00 - 13:00
Every Thursday at 12:00 in Grey Room 3.

Seminar: 'Reviving PBHs: primordial black holes from supercooled phase transitions revisited'
2026-01-22 15:00 - 16:00
Speaker: Piotr Toczek (Warsaw University)
Venue & Time: 15:00 / Red Room
Abstract: Primordial black holes, hypothetical objects that may have formed in the early Universe through the interplay between high-energy physics and gravity, are very appealing candidates for dark matter. In this seminar, I will discuss their formation as a result of the collapse of energy density fluctuations originating from supercooled first-order phase transitions. I will present the formalism that we use to track the evolution of such fluctuations in a fully covariant manner, explicitly incorporating the spacetime metric perturbations. I will show which aspects of the phase transition drive the growth of density fluctuations and their gravitational collapse, and identify the transitions for which the produced population of primordial black holes may constitute a significant fraction of the total dark matter abundance.

Old Journal Club: 'Particle Spectrum in Quantum Field Theory'
2026-01-22 17:00 - 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Alejandro Puga (IFT) will present “Particle Spectrum in Quantum Field Theory” de Alexander M. Polyakov (JETP Lett. 20 (1974) 194-195)

Abstract: We investigate the nonperturbative structure of quantum field theories and its consequences for the physical spectrum of excitations. Emphasis is placed on the role of instantons—topologically nontrivial field configurations—which contribute essentially to tunneling processes and mass generation beyond perturbation theory. The analysis demonstrates how instanton effects modify correlation functions and lead to qualitatively new features in the particle spectrum, highlighting the deep connection between topology, symmetry, and dynamics in quantum field theory.

Venue & Time: Blue Room / 17:00

Cosmology Journal Club
2026-01-27 14:00 - 15:00

ML-AI-HPC Jounal Club: 'Probabilistic modeling and Bayesian inference for collider data'
2026-01-29 11:00 - 13:00 | Gray Room 1, Instituto de Física Teórica, C/ Nicolás Cabrera 13-15, Cantoblanco, Madrid, Madrid, 28049, Spain
Title: ‘Probabilistic modeling and Bayesian inference for collider data’
Speaker: Santiago Tanco (IFLP-CONICET/UNLP)
Venue&Time: Gray Room 1 / 11:00

Polygonal Gravity Seminars
2026-01-29 11:30 - 16:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Madrid’s Polygonal Gravity Seminar Series
Wednesday, January 29th. Blue Room (IFT)

11:30h First talk

Speaker: Robie Hennigar (U. Durham, UK)
Title: Building Regular Black Holes

Abstract: The study of regular (singularity-free) black holes has a long
history, but progress has been limited by the absence of a dynamical
framework in which they form and by conceptual issues at the kinematical
level. In this talk I will discuss recent work in which spherically
symmetric regular black holes emerge as unique solutions of gravity
theories with infinite towers of higher-curvature corrections, enabling
explicit analyses of their formation and dynamics. I will review the
construction, summarize key results, and highlight open problems.

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12:45-14:15 Lunch break

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14:30h Second talk

Speaker: 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 for new physics.

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More information about these and following monthly seminars can be found at the webpage

SPS Journal Club: 'Mapping moduli across heterotic conifolds'
2026-01-29 12:00 - 13:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Strings, Pheno and the Swampland Journal Club

Title: ‘Mapping moduli across heterotic conifolds’

Speaker: Christian Aoufia (IFT)

Venue & Time: Red Room / 12:00

Abstract: In this work, we provide evidence for a duality between 4-dimensional Calabi-Yau compactifications of the heterotic string, in which the base manifolds are linked by a conifold transition. In recent work, a geometric proposal was put forward for how 5-branes and gauge bundles are carried across such transitions. It was observed that compactifications connected in this way lead to 4-dimensional effective theories with the same massless spectrum. Here we provide much stronger evidence that these heterotic conifold transitions do indeed lead to dual theories. We construct a duality map between the field spaces of the two compactifications and use it to demonstrate the agreement of large numbers of holomorphic functions appearing in the definition of the effective theories. In an example, we show that 147,440 independent superpotential Yukawa couplings agree across the duality as holomorphic functions of the moduli. In certain special cases, the putative duality studied here reduces to the target space duality of (0,2) gauged linear sigma models.

Pheno Journal Club: 'GeV-scale QCD Axion'
2026-01-29 12:00 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘GeV-scale QCD Axion’

Speaker: Thomas Steingasser (IFT)

Venue & Time: 12:00 / Gray Room 3

Abstract: In order to solve the strong CP problem, we study the possibility that the Peccei–Quinn symmetry is broken below the QCD scale. We find that a QCD axion can be above GeV, and may be among the observed η resonances. It is immune to quantum gravity corrections. The only fermion that has a U (1) Peccei–Quinn charge is the right-handed up quark. Flavor-changing neutral currents are surprisingly small, except for a possible but not necessary contribution to D0–D0 mixing. All accelerator and astrophysical limits can be evaded. The most significant constraint is the mass splitting between π± and π0. In a UV completed model, LHC can look for a dijet resonance in u ̄u,u ̄d, d ̄u channels.

Seminar by Ennio Salvioni (IFAE): 'Probing the Dark Sector with Large Scale Structure'
2026-01-29 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘Probing the Dark Sector with Large Scale Structure’
Speaker: Ennio Salvioni (IFAE)
Venue&Time: Red Room / 15:00
Abstract: Precision cosmology offers opportunities to test the nature of dark matter independently of any interactions with the visible sector. I will discuss how data from galaxy surveys, including the ongoing DESI and Euclid projects, can be leveraged to probe new dynamics in the dark sector. For this purpose, I will show how to extend the Effective Field Theory of Large Scale Structure to include physics beyond the Standard Model, enabling perturbative computations of the power spectrum of galaxies. The scenarios I will discuss include long-range dark matter self-interactions, and sub-components of dark matter exhibiting suppressed growth of structure, such as ultra-light axions or light thermal relics.
This seminar is related to the I+D+i project whose reference is CEX2020-001007-S, funded by MCIN/AEI/10.13039/501100011033. The topic is framed within the following research line: Origin and composition of the universe: Astroparticles and Cosmology (Astro/Cosmo).
