Instituto de Física Teórica

SPS Journal Club: 'Anomaly-induced vanishing of brane partition functions'
2026-02-26 12:00 - 13:00 (Europe/Madrid) | 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 (SPS)
Speaker: Michelangelo Tartaglia (IFT)
Title: ‘Anomaly-induced vanishing of brane partition functions’
Abstract: In the presence of ‘t Hooft anomalies, backgrounds for the symmetries of a quantum field theory can lead to non-conservation of Noether currents, or more generally, to the presence of charged insertions in the path integral. When there is a net background charge, the partition function evaluated on closed manifolds will vanish. For anomalous symmetries, this statement can also be understood as the anomaly theory giving rise to a non-trivial anomalous phase for the partition function even for “rigid” transformations which leave all background fields unchanged. We use the generalisation of this second viewpoint to the setting of anomalous higher-form symmetries in order to show vanishing of the partition function for a number of examples, both with and without a Lagrangian description. In particular, we show how to derive from these considerations the analogue of the Freed-Witten anomaly cancellation condition for the M5-brane, and also that for the D3-brane in S-fold backgrounds.

Pheno Journal Club
2026-02-26 12:00 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Every Thursday at 12:00 in Grey Room 3.

Seminar: 'Sub-PeV gamma-ray astronomy and its physics'
2026-02-26 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: ‘Sub-PeV gamma-ray astronomy and its physics’
Speaker: Sei Kato (Sorbonne Université, Institut d’Astrophysique de Paris)
Venue&Time: Red Room / 15:00
Abstract: This talk will focus on the physics that can be explored with sub-PeV gamma-ray astronomy (E > 10^14 eV), particularly on the Galactic diffuse gamma rays and the dark matter. Also, our project called ALPACA, which aims systematic sub-PeV gamma-ray observations in the southern sky for the first time in the world, is detailedly presented.

Old Journal Club: 'Generalized Global Symmetries'
2026-02-26 17:00 - 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Miquel Aparici Domingo (IFT) will present Generalized Global Symmetries by Davide Gaiotto, Anton Kapustin, Nathan Seiberg, Brian Willett, JHEP 02 (2015) 172

Abstract:
A q-form global symmetry is a global symmetry for which the charged operators are of space-time dimension q, e.g. Wilson lines, surface defects, etc., and the charged excitations have q spatial dimensions, e.g. strings, membranes, etc. Many of the properties of ordinary global symmetries (q = 0) apply here. They lead to Ward identities and hence to selection rules on amplitudes. Such global symmetries can be coupled to classical background fields and they can be gauged by summing over these classical fields. These generalized global symmetries can be spontaneously broken (either completely or to a sub-group). They can also have ’t Hooft anomalies, which prevent us from gauging them, but lead to ’t Hooft anomaly matching conditions. Such anomalies can also lead to anomaly inflow on various defects and exotic Symmetry Protected Topological phases. Our analysis of these symmetries gives a new unified perspective of many known phenomena and uncovers new results.

Seminar: 'The tensions of LCDM: An update of observations and theoretical implications'
2026-03-02 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: ‘The tensions of LCDM: An update of observations and theoretical implications’
Speaker: Leandros Perivolaropoulos (Ioannina)
Venue&Time: Red Room / 15:00
Abstract: The standard LCDM cosmological model, despite its success in describing the large-scale structure of the Universe, is currently challenged by statistically significant discrepancies between early and late-universe observations. In this talk, I provide a comprehensive update on observational status and theoretical implications of three major tensions: the Hubble (H0) constant discrepancy, the DESI DR2 Phantom-Crossing Anomaly, and the S8 tension. First, I re-examine the H0 tension by classifying 88 Sound-Horizon-Free measurements. This analysis reveals that the discrepancy is not merely an “Early vs. Late” issue but is fundamentally driven by a clash between the Distance Ladder and the majority of other probes (reaching a significance of ~ 6.5sigma). I will further discuss why simple late-time modifications to the expansion history fail to solve this tension due to constraints from unanchored Type Ia Supernovae (Pantheon+), effectively establishing a “no-go” theorem for such solutions.
Second, I address the implications of the recent DESI DR2 data, which favors a dynamical dark energy equation of state crossing the phantom divide (w(z) < -1). While this behavior is forbidden in simple quintessence models within General Relativity, I demonstrate how it can be naturally accommodated in reconstructed Scalar-Tensor theories. By allowing for an evolving effective gravitational constant (G_eff), these models can fit the phantom crossing while simultaneously alleviating the Hubble tension. Finally, I review the current landscape of the S8 tension. I discuss the shift toward a “Combined CMB” baseline (Planck + ACT + SPT) which reduces uncertainties, and analyze the dichotomy currently present in weak lensing surveys (e.g., DES Year 6 vs. KiDS Legacy). I conclude by summarizing which theoretical extensions of LCDM remain viable in the face of these combined precision constraints. (edited)

Cosmology Journal Club
2026-03-03 10:00 - 11:00 | 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.

Holo Club: 'Brick wall Normal Modes and Emerging Thermality'
2026-03-03 11:30 - 13:00 | Gray Room 1, Instituto de Física Teórica, C/ Nicolás Cabrera 13-15, Cantoblanco, Madrid, Madrid, 28049, Spain
Speaker: Suman Das (IFT)
Title: ‘Brick wall Normal Modes and Emerging Thermality’
Venue & Time: Gray Room 1 / 11:00
Abstract:
arXiv:2401.01417
The ’t Hooft brick wall model provides one of the earliest microscopic derivations of the black-hole area law within the probe approximation of quantum field theory in curved spacetime. In this talk, I will revisit the original construction and present a modern perspective based on the spectral properties of the probe fields. After briefly reviewing how the area-proportional entropy arises in ’t Hooft’s setup, I will show that its origin can be understood in terms of the structure of the normal-mode spectrum. In particular, a quasi-degenerate growth of states along a specific quantum-number direction leads directly to the area scaling of the entropy.This viewpoint not only clarifies the mechanism behind the entropy but also reveals a number of non-trivial features of the spectrum, including signatures commonly associated with quantum chaos. I will discuss these features. Finally, I will show that, when the brick wall is placed parametrically close to the horizon, the two-point function of the probe field becomes indistinguishable from a thermal correlator, providing a precise sense in which thermality emerges in this framework.

Shannon's Corner Journal Club
2026-03-05 11:30 - 17:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Venue & Time: Gray Room 3 / 11:30
Speaker: Franco Salinas Pytel (UCM)
Abstract: “The debates between Einstein and Bohr on the foundations of quantum
mechanics culminated in one of the most iconic statements in the
history of physics: “God does not play dice.”
In their seminal 1935 paper, Albert Einstein, Boris Podolsky, and
Nathan Rosen argued that if locality is to be maintained, then quantum
mechanics must be incomplete.
In this talk, I will present a concise overview of the original EPR
argument, Bell’s theorem and its experimental confirmation. I will
then explore quantum non-locality through the framework of XOR games,
highlighting their connections to foundational questions in
mathematics.”

Pheno Journal Club
2026-03-05 12:00 - 13:00 | 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 2.

SPS Journal Club: 'Self-gravitational Effects in the Black Hole-Tower Correspondence'
2026-03-05 12:00 - 17:00 | 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: ‘Self-gravitational Effects in the Black Hole-Tower Correspondence’
Venue&Time: Red Room / 12:00
Speaker: Miquel Aparici (IFT)
Abstract: It is well-known that in weak coupling and near decompactification limits, towers of light particles appear in the spectrum of gravitational theories. These towers can be postulated to correspond to minimal black holes in a framework known as the black hole-tower correspondence. We study the transition from towers of particles to black holes and analyze self-gravitational effects of the tower as the EFT cutoff is approached.

Seminar: 'Cosmological Magnetic Fields from Ultralight Dark Matter'
2026-03-05 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
Title: Cosmological Magnetic Fields from Ultralight Dark Matter
Speaker: Robert Brandenberger (McGill)
Venue&Time: Red Room / 15:00
Abstract: A coherently oscillating ultralight dark matter field which couples to electromagnetism in the same way as an axion induces a tachyonic instability which leads to the generation of cosmological magnetic fields immediately after the time of recombination. The mechanism also opens up channels which can facilitate the formation of supermassive black holes.

Seminar: 'How string theory computes quantum gravity amplitudes'
2026-03-09 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: ‘How string theory computes quantum gravity amplitudes’
Speaker: Lorenz Eberhardt (U. Amsterdam)
Venue&Time: Red Room / 15:00
Abstract: String theory provides a framework in which quantum gravitational scattering amplitudes are ultraviolet finite and computable in perturbation theory. These amplitudes are defined by integrating over the moduli space of Riemann surfaces, replacing the Feynman diagram expansion of field theory by a sum over worldsheet topologies. I will review how this definition arises and explain structural properties such as UV-finiteness, dual resonance and their Regge behavior. I will then discuss recent progress in explicit computations, focusing on one-loop amplitudes and new results on their high-energy behavior.

Cosmology Journal Club
2026-03-10 14:00 - 15:00, 2026-03-17 14:00 - 15:00 | Madrid

SPS Journal Club: 'Quantum Obstructions to N=1 Infinite Distance Limits'
2026-03-12 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: ‘Quantum Obstructions to N=1 Infinite Distance Limits’
Speaker: Jeroen Monnee (U. Hamburg)
Venue&Time: Red Room / 12:00
Abstract: We study limits in the field space of 4d N=1 orientifold compactifications of Type IIB string theory with O3/O7-planes that descend from infinite distance limits in the complex structure moduli space of the underlying Calabi-Yau threefold. In particular, we investigate the fate of such limits in the quantum-corrected field space. We find that such orientifolds can be grouped into two classes, dubbed O-type A/B, whose behaviours vary dramatically at the quantum level. For O-type A limits, we observe that g_s-corrections become unsuppressed by observing that the degeneration of the geometry in the F-theory lift differs drastically from classical expectations. For O-type B limits we instead observe a similar behaviour for alpha’-corrections, based on the classical inconsistency of EFT string probes combined with explicit computations of such corrections. Based on upcoming work with Lukas Kaufmann, Timo Weigand, and Max Wiesner.

Pheno Journal Club
2026-03-12 12:00 - 15:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Every Tuesday at 15:00 in Grey Room 3.

Seminar: 'Effective Field Theory for Thermal Phase transitions'
2026-03-16 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; ‘Effective Field Theory for Thermal Phase transitions’
Speaker: Mikael Chala (Granada)
Venue&Time: Red Room / 15:00
Abstract: I will present recent progress in applying effective field theory (EFT) to the precise computation of thermal phase transition parameters and the associated gravitational wave spectra. I will also briefly comment on byproducts of this work, including new methods for two-loop renormalization in EFT or skyrmion degrees of freedom emerging only at finite temperature.

DIFT Colloquium: 'The Mystery of Cosmic Acceleration'
2026-03-18 15:30 - 17:00 | IFT Auditorium, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, Madrid, 28049,, Spain
Title: The Mystery of Cosmic Acceleration

Speaker: Prof. David Weinberg, The Ohio State University, USA

Date and time: 15:30h (CET), Wednesday, March 18th, 2026

Location: CFTMAT Auditorium

After the talk, we will have a coffee gathering, providing an opportunity to continue the discussion and interact with the speaker in an informal setting.

Zoom link:
https://us02web.zoom.us/j/87376882248?pwd=[REDACTED]

Abstract:
Cosmic acceleration is one of the most surprising cosmological discoveries
of the past century. Even the “simplest” explanations require new,
cosmologically dominant energy components with exotic physical properties.
Current and near-future experiments are seeking clues to the origin of
cosmic acceleration by measuring the history of expansion and structure
growth with sub-percent precision over a wide span of redshift. I will
review the observational methods that underpin these measurements
and assess the current state of play, with particular attention to recent
measurements from the Dark Energy Spectroscopic Instrument (DESI) which
suggest that the properties of dark energy are evolving at a startling rate.
I will discuss the prospects and challenges for the new generation of
experiments — DESI, the Euclid mission, the Vera Rubin Observatory,
and the Nancy Grace Roman Space Telescope — which aim to sharpen cosmological
measurements by a factor of ten.

SPS Journal Club: 'Axion-Scalar Systems and Dynamical Distances'
2026-03-19 12:00 - 13:00 | Madrid
Strings, Pheno and the Swampland (SPS) Journal Club
Speaker: Gonzalo F. Casas (IFT)
Title: ‘Axion-Scalar Systems and Dynamical Distances’
Abstract: We study the cosmology of axion-scalar pairs, coupled by a hyperbolic field-space metric and with a string-motivated rational scalar potential. Borrowing tools from the theory of dynamical systems, we are able to classify all late-time trajectories and extract physical properties of the asymptotic solutions. These results suggest a Dynamical Distance Conjecture: along the physical (possibly non-geodesic) trajectories, towers of states become exponentially light as a function of the traversed field-space distance. We further rule out possible counterexamples with wildly oscillating solutions. The considered axion-scalar systems are realized in F-theory compactifications, where the axion-scalar pair is a complex-structure modulus and four-form fluxes induce the asymptotic potentials. We also provide a complete Hodge-theoretic classification of all one-modulus asymptotic potentials of this type.

Seminar: 'Beyond the Minimal Axion: Robustness of Standard Predictions'
2026-03-19 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: ‘Beyond the Minimal Axion: Robustness of Standard Predictions’
Speaker: Sung Mook Lee (CERN)
Venue & Time: Red Room / 15:00
Abstract: The QCD axion is one of the most compelling candidates for physics beyond the Standard Model, as it can simultaneously solve the strong CP problem and account for the dark matter abundance. In the minimal single-axion framework, especially in a post-inflationary cosmology, the combination of axion gauge coupling quantization and axion production from string networks leads to sharp and highly predictive targets. In this talk, we revisit these predictions in a simple but realistic setup with an additional confining dark gauge group and extra axion degrees of freedom. We will show how axion mixing and defect dynamics can modify both the coupling predictions and the relic abundance expectations through emergent features specific to multi axion scenarios, and discuss when the standard single axion benchmarks remain reliable. This provides a useful test of what remains truly robust in extended axion theories and helps guide current experimental targets.

Seminar: 'Observing Quantum Gravity in Extremely Cold Horizons'
2026-03-23 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: ‘Observing Quantum Gravity in Extremely Cold Horizons’
Speaker: Roberto Emparan (Universidad de Barcelona)
Venue&Time: Red Room / 15:00
Abstract: Recent developments have revealed that black holes near extremality exhibit large quantum fluctuations in their geometry, marking a controllable breakdown of semiclassical quantum field theory in curved spacetime. In this talk, I will discuss how these fluctuations can be revealed through scattering waves off the black hole. In particular, we find that extremely cold black holes become transparent to low-frequency light or gravitational radiation. Although such signatures are extraordinarily hard to detect, they provide concrete signatures of quantum gravity at play in near-extremal regimes.

Cosmology Journal Club
2026-03-24 14:00 - 15:00, 2026-04-07 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

IFT Colloquium: 'QCD critical point and the predictable randomness of relativistic fluids'
2026-03-25 12:00 - 13:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘QCD critical point and the predictable randomness of relativistic fluids’
Speaker: Misha A. Stephanov (Illinois U., Chicago)
Venue&Time: 12:00 / Red Room
Abstract: Quantum Chromodynamics predicts a variety of unusual states of matter in which relativity and quantum many-body physics strongly intertwine. Discovering phase transitions between these extreme forms of matter in a laboratory is an unprecedented task. This is the challenge heavy-ion collision experiments are taking up at the Relativistic Heavy-Ion Collider (RHIC) and future facilities. An intriguing open question is the existence and the location of the QCD critical point. Similar critical points are ubiquitous in earthly substances and the associated fluctuation driven phenomena are remarkably universal. Can the QCD critical point be discovered in the heavy-ion collision experiments? It is a nontrivial question in large part because of the importance of the explosive dynamics of the collision. This challenging question is a subject of current research and a major motivation for recent developments in relativistic hydrodynamics. Of particular interest in this context is the dynamics of thermal fluctuations inherent in any system with dissipation.

Quantum Information Journal Club: 'Rapid mixing for Gibbs measures in Riemannian manifolds'
2026-03-25 14:30 - 15:30 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Speaker: Pablo Páez-Velasco (Universidad Complutense de Madrid)
Venue & Time: Gray Room 2 / 14:30
Abstract: Given some sufficiently smooth, generally non-convex, function F on a Riemannian manifold, and a fixed inverse temperature, the problem of sampling with respect to the associated Gibbs distribution has played a central role in several areas, such as statistical mechanics or non-convex optimization. A natural approach to do so is to simulate the Langevin diffusion associated to F, whose stationary distribution is precisely the Gibbs distribution. However, obtaining quantitative convergence guarantees in this non-convex, geometric setting remains difficult.
In this work, we identify a set of assumptions on F and the underlying manifold under which a log-Sobolev inequality (LSI) holds for the Gibbs distribution in the low-temperature regime. As a consequence, we obtain exponential convergence of the Langevin diffusion to its stationary distribution.

Pheno Journal Club: 'Powerful Yukawas'
2026-03-26 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Every Thursday at 12:00 in Grey Room 2.
Marta Fuentes (IFT), will present “Powerful Yukawas”.

We introduce a class of models where the masses of the light Standard Model fermions are due to an Effective Field Theory operator that appears beyond dimension-4 in the power counting expansion, resulting in a `Powerful Yukawa’. The effective Yukawa coupling structure is UV-completed using a collective symmetry breaking pattern in the flavour sector, which we dub `Sprouted Symmetry Breaking.’ The irreducible signature is an enhanced Higgs coupling to the light Standard Model fermions.

SPS Journal Club: 'M-theory on S^1 vee S^1 as Type 0A'
2026-03-26 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 & The Swampland Journal Club | Every Thursday at 12:00 in the Red Room.
Speaker: Salvatore Raucci (IFT)
Title: ‘M-theory on S^1 vee S^1 as Type 0A’
Abstract: We propose an exotic geometric M-theory dual for the weak coupling Type 0A string: compactification on a sub-Planckian S^1 vee S^1 (two circles connected at a point), where strong quantum effects lead to fields living on distinct resolutions of that space. Moreover we argue that tachyon condensation of the 0A theory corresponds to shrinking of one of the two circles leading to the IIA supersymmetric string. We use this and other dualities to provide an F-theoretic description of the axio-dilaton and the tachyonic field of Type 0B and argue for the existence of a strong coupling critical point of the potential using the resulting duality symmetry Γ_0(2) ⊂ SL(2,Z). The existence of this critical point can also be argued using conventional M-theory dualities. If this critical point is unique it is an unstable dS vacuum. Using this we propose a strong coupling conformal fixed point for a non-supersymmetric gauge theory in four dimensions living on coincident D3^+ — D3^- branes of 0B.

HoloClub: 'Semi-classical aspects of black holes: recent progress and future directions'
2026-04-07 11:30 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘Semi-classical aspects of black holes: recent progress and future directions’
Speaker: Juan F. Pedraza (IFT)
Venue & Time: Gray Room 3 / 11:30
Abstract: Semi-classical gravity provides a valuable framework for exploring quantum effects in black hole physics, particularly in regimes where a complete theory of quantum gravity remains out of reach. In this talk, I will review recent progress in the description of black holes in braneworld gravity, where holographic constructions allow semi-classical backreaction to be incorporated in a controlled manner. I will discuss how these setups give rise to quantum-corrected black hole solutions and why they provide a promising arena for black hole phenomenology. In the final part of the talk, I will outline a few possible calculations and open directions, emphasizing concrete questions that may be worth pursuing in future work.

Pheno Journal Club
2026-04-09 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain

Strings, Pheno and the Swampland (SPS) Journal Club
2026-04-09 12:00 - 17:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Every Thursday at 12:00 in the Red Room.
