LHC Working Group on Forward Physics and Diffraction
2025-09-29 09:00 - 2025-10-02 18:30 (Europe/Madrid) | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
The September 29-October 2 2025 four-day workshop in Madrid of the LHC Physics Centre at CERN (LPCC) Forward Physics Working Group provides a forum at CERN for experimental collaborations and theorists to meet and exchange latest results across all topics of forward physics at the LHC.
The workshop will take place at the Institute of Theoretical Physics (Campus de Cantoblanco 28049 Madrid Spain) and we will be hosted by Prof. Agustin Sabio Vera. To come to IFT, you can take Line C-4 (Colmenar Viejo or Alcobendas/San Sebastián de los Reyes), that takes you to the University (Cantoblanco-Universidad Station). You can pick it up in Atocha (main station in the Centre/South of Madrid), Nuevos Ministerios (Paseo de la Castellana) and Chamartín (main station in the North). After Chamartín, the second station is Cantoblanco-Universidad, where you should exit.
More info.

Muon g-2: nuts and bolts and lattice QCD
2025-09-29 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
Speaker: Andreas Kronfeld (Fermilab)
Venue&Time: Red Room / 3:00 PM
Abstract: This seminar consists of two parts. First, it is discussed how various approaches to the hadronic vacuum polarization (HVP) for the anomalous magnetic moment of the muon, g-2, are connected. Second, results for the HVP from lattice QCD are presented, focusing on the work of the Fermilab Lattice, HPQCD, and MILC collaborations.

Seminar by Roberto Vega-Morales
2025-09-29 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
Speaker: Roberto Vega-Morales from Granada U.

Venue&Time: Red Room / 3:00 PM

Abstract: TBA

SPS Journal Club: 'Landau-Ginzburg Models and Flux Vacua'
2025-10-02 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: Muthusamy Rajaguru (IFT Madrid)

Venue&Time: Red Room / 12:00 PM

Abstract: In this talk, I will give an overview of recent progress that has been made in constructing non-geometric flux vacua. In particular, I will focus on type IIB string compactifications where the internal geometry is described by the 2^6 and 1^9 Landau-Ginzburg (LG) models. These LG models have no Kähler moduli and allow us to realize GKP-type vacua explicitly in the interior of the complex structure moduli space. I will summarize the properties of these vacua and their implications for certain Swampland conjectures.

Relevant literature – 2503.16599, 2407.16756, 2407.16758, 2406.03435, 2306.15714, 2203.15818

Fast inference for slow likelihoods with probabilistic machine-learning
2025-10-02 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
Speaker: Jesús Torrado from IEM-CSIC

Venue&Time: Red Room / 3:00 PM

Abstract: Inference for slow likelihoods can require weeks or months, if possible at all, with traditional Monte Carlo samplers. This would be the case, for example, when fitting expensive non-linear matter spectrum models, or when characterizing individual long-duration GW events. I will introduce a fast machine-learning Bayesian inference algorithm for general non-Gaussian posteriors with a moderate number of parameters. I will present a pedagogical discussion of some general aspects of it, such as dealing with the curse of dimensionality, characterizing a region of interest, or parallelising active learning. I will show that the total number of expensive likelihood evaluations can be reduced by at least two orders of magnitude compared to traditional Monte Carlo methods, at low overhead costs and no pre-training. I will demonstrate its performance on a couple of real cosmological and GW problems.

César Gómez (1954–2025): A rich life in theory
2025-10-03 10:00 - 17:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Venue&Time: Blue Room / 10:20 – 17:30
More info: workshops.ift.uam-csic.es/CesarGathering/
César Gómez, whose profound contributions to gauge theory, string theory and quantum gravity were matched by his vision and generosity, passed away on 7 April 2025. After earning his PhD in Salamanca, he held positions at Harvard, the IAS and CERN before joining the CSIC in Madrid, where he became a founding member of the Instituto de Física Teórica, his true scientific home.
His career spanned key areas of theoretical physics: from the quantum vacuum in QCD and two-dimensional conformal field theory to holography, black holes and the quantum structure of spacetime. In recent years he embarked on bold new ideas about symmetry breaking and the quantum origin of the universe, entering one of his most creative periods when his life was cut short.
Beyond his scientific achievements, César was a gifted teacher, an inspiring presence at seminars and a remarkable conversationalist. He leaves behind not only a lasting scientific legacy, but also the memory of a colleague and friend who enriched every exchange with curiosity, insight and humanity.
The meeting will be an opportunity to celebrate Cesar’s life and career through the personal recollections of some of his friends and collaborators.
Read CERN’s obituary

Cosmology Journal Club
2025-10-07 14:00 - 15:00, 2025-10-14 14:00 - 15:00, 2025-10-21 14:00 - 15:00, 2025-10-28 14:00 - 15:00, 2025-11-04 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.

SPS Journal Club: Symmetric Moduli Spaces, the Swampland Distance Conjecture (...and the Emergent String Conjecture?)
2025-10-09 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: Bernardo Fraiman (IFT)

Venue&Time: Red Room / 12:00

Abstract: For non-compact, locally symmetric moduli spaces M, the set of geodesics and the geometry of the boundary can be completely characterised using group theory. Under the assumption that M is “compactifiable” and some mild conditions on the spectrum of states, we prove the SDC for all locally symmetric spaces. We show that the states necessarily transform in some representation of the local isometry group, and that the convex hull encoding the exponential rate at which the leading tower of states becomes light coincides with the convex hull of the weights of the representation.

In this talk I will discuss briefly some aspects of the proof, the domain of applicability of our assumptions and their limitations. If time permits, I will also explain how the relation between towers and weights allows one to classify moduli spaces, particle state representations and space time dimensions compatible with the Emergent String Conjecture. Based on 2508.18401 and work in progress.

Large neutrino mass in cosmology and keV sterile neutrino dark matter from a dark sector
2025-10-09 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
Speaker: Thomas Schwetz from Karlsruhe Institute of Technology (KIT)

Venue&Time: Red Room / 3:00 PM

Abstract:
Recent results from cosmology place sever upper bounds on the sum of neutrino masses, starting to be in conflict with lower bounds from neutrino oscillations. If this neutrino tension persists, it may indicate new physics in cosmology and/or neutrino physics. After a brief review of the present state, I discuss a new physics scenario able to explain this tension. It is based on an extended seesaw model for neutrino mass, including a number of massless neutrinos acting as dark radiation, as well as a keV state as a dark matter candidate. The dark sector is brought into equilibrium with neutrinos between BBN and recombination. This scenario predicts a slight increase in the effective number of neutrino species Neff at recombination, potentially detectable byfuture CMB missions.

Holo Club: Explicit Connections Between Krylov and Nielsen Complexity
2025-10-14 11:30 - 13:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Le-Chen Qu (IFT)

Venue&Time: Grey Room 3 / 11:30

Abstract: We establish a precise correspondence between Krylov complexity and Nielsen complexity in quantum many-body systems. By identifying the Krylov basis with the generators of elementary gates in Nielsen’s geometric framework, the Krylov complexity of precursor operators acquires a geometric interpretation as the length of straight-line paths in Nielsen geometry. This construction provides an upper bound on Nielsen complexity, which becomes exact in the small-precursor limit. Employing the SYK model as a test case, we demonstrate that the straight-line trajectory satisfies the Nielsen geodesic equation and remains both locally and globally minimizing up to a critical value of $z$, beyond which conjugate points and geodesic loops arise. Within this framework, cost functions quadratic in the Krylov index are further shown to reproduce the conjectured proportionality between the complexity growth rate and the operator size.

Machine Learning and AI Journal Club
2025-10-16 11:00 - 12:00 | Gray Room 1, Instituto de Física Teórica, C/ Nicolás Cabrera 13-15, Cantoblanco, Madrid, Madrid, 28049, Spain
Venue&Time: Grey Room 1

SPS Journal Club: 'Probing the Rigidity of String Theory'
2025-10-16 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: Georgina Staudt (Max Planck Institute Munich)

Venue&Time: Red Room / 12:00

Abstract: We investigate the deformability of the Veneziano amplitude. If string theory is the unique theory of quantum gravity, the tree level amplitudes of weak coupling limits should be non-deformable. We make progress in this direction for tachyon-free superstring theories by deriving a general positivity bound and excluding some specific families of deformations.

DIFT Colloquium: 'Gamma Ray Bursts, Cosmic Rays and the Sociology of Science'
2025-10-16 15:30 - 17:00 | AULA POLIVALENTE UAM, Plaza Mayor Campus de Cantoblanco UAM. C. Einstein, 7, Fuencarral-El Pardo, 28049 Madrid, Madrid, Madrid, 28049,, Spain
Speaker: Álvaro de Rújula from IFT & CERN

Venue & Time: Aula Polivalente UAM
Abstract:
Gamma-Ray Bursts (GRBs) and Cosmic Rays (CRs) are not difficult to comprehend. Quasars and micro-quasars are seen to emit highly relativistic “Cannonballs” (CBs), though the underlying mechanism remains unfathomable. The observation that core-collapse supernovae also emit CBs —plus some trivial relativistic kinematics— provides a successful understanding of GRBs and CRs. The self-defined “official experts” on these fields resist the evidence, in an explicitly inquisitorial way.

This colloquium 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).

Old Journal Club: 'Renormalization and Effective Lagrangians'
2025-10-16 17:00 - 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Pau Garcia Romeu (IFT) will present Renormalization and Effective Lagrangians by Joseph Polchinski.

Venue&Time: Blue Room / 17:00

Abstract:

There is a strong intuitive understanding of renormalization, due to Wilson, in terms of the scaling of effective lagrangians. We show that this can be made the basis for a proof of perturbative renormalization. We first study renormalizability in the language of renormalization group flows for a toy renormalization group equation. We then derive an exact renormalization group equation for a four-dimensional λø 4 theory with a momentum cutoff. We organize the cutoff dependence of the effective lagrangian into relevant and irrelevant parts, and derive a linear equation for the irrelevant part. A lengthy but straightforward argument establishes that the piece identified as irrelevant actually is so in perturbation theory. This implies renormalizability. The method extends immediately to any system in which a momentum-space cutoff can be used, but the principle is more general and should apply for any physical cutoff. Neither Weinberg’s theorem nor arguments based on the topology of graphs are needed.

More info: https://inspirehep.net/literature/189574

Pheno Journal Club: Coherently enhanced decoherence and cloud substructure of atom interferometers
2025-10-21 15:00 - 16:00 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Pablo Blanco Mas (IFT)

Venue & Time: Grey Room 3 / 15:00

Abstract: We study how coherent scattering of a background gas off an atom (or other matter) interferometer can lead to enhanced signals from phase shifts and contrast loss. We focus on the inclusion of realistic features of atom interferometers such as finite temperature, cloud substructure, and time-dependent cloud radii. The inclusion of these effects, extending beyond the previously considered point-like cloud approximation, naturally allow us to study the smooth transition between the coherent and incoherent scattering regimes. We discuss how the formalism presented herein can be tested in the laboratory (with near-infrared photons or an eV-scale electron gun), and discuss an application for the detection of dark matter interacting via long-range forces.

SPS Journal Club: Inflationary Particle Production and the Swampland
2025-10-23 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: Joaquin Masias (Munich, Max Planck Institute)
Venue&Time: Red Room / 12:00 PM
Abstract: TBA

Bubble wall dynamics from nonequilibrium quantum field theory
2025-10-23 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
Speaker: Matthias Carosi from Munich, Tech. U.

Venue & Time: Red Room / 15:00

Abstract:

First-order phase transitions in the early universe are a unique probe of physics beyond the Standard Model, with potential implications for electroweak baryogenesis, the formation of primordial black holes, magnetogenesis and the production of dark matter. Upcoming gravitational wave detectors may capture the imprint of such transitions, but to extract theoretical insights from these signals requires a precise understanding of the underlyingdynamics.
In this talk, I show how the language of nonequilibrium quantum field theory, combined with the two-particle-irreducible effective action, provides anatural framework for describing the dynamics of a bubble after nucleation. After a brief introduction to the closed-time-path formalism, I derive the dynamical equations governing the bubble and the plasma, and identify all sources of friction for thebubble expansion. This framework unifies the pre-existing approaches within a single, consistent description. In the ultrarelativistic regime, I demonstrate how to compute the friction induced by the pair production of heavy scalar particles and outline the contributions of particle mixing andtransition radiation.

Recent results on the origin of Galactic CRs from gamma-ray astronomy
2025-10-27 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: Guillem Martí-Davesa (INFN-Trieste)

Venue&Time: Red Room / 15:00

Abstract: Supernovae have traditionally been invoked as the dominant cosmic ray factories within our Galaxy, capable of accelerating protons up to PeV energies. In this seminar we will discuss to what extent such a view holds today, and if alternative source populations could instead be relevant actors. Thus, a comprehensive review of recent findings on supernovae, stellar clusters, and microquasars will be presented, with particular emphasis on observational signatures above GeV energies.

Seminar: 'Entanglement asymmetry and spontaneously broken symmetries'
2025-10-28 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: Eduardo García-Valdecasas (SISSA, Trieste)
Venue&Time: Red Room / 15:00
Abstract: Entanglement asymmetry is a relative entropy that faithfully measures the breaking of a symmetry in a subregion. We explore some applications in theories with spontaneously broken higher form symmetries. We will start with discrete abelian symmetries and then discuss continuous symmetries. We will be able to recover the Mermin-Wagner-Coleman theorem and refine it for the case of subregions.

Pheno Journal Club
2025-10-28 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: Randomized truncation
2025-10-29 11:30 - 12:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Aram Harrow (MIT)
Venue&Time: Grey Room 3 / 11:30
Abstract: Given a vector v, what is the closest k-sparse vector? The answer to this question is usually that we should take the largest k entries of v. It turns out that we can do better with randomized approximations. When approximating pure bipartite entangled states with states of low Schmidt rank, this means that mixed approximations outperform pure approximations. This fact has application to classical algorithms for matrix product states by improving the truncation step, and to quantum algorithms for Hamiltonian simulation.
Joint work with Angus Lowe and Freek Witteveen.
https://arxiv.org/abs/2510.08518

SPS Journal Club: Weak Gravity and Perturbative Black Holes
2025-10-30 12:00 - 13:00
Speaker: Matteo Lotito (IFT)
Venue&Time: Red Room / 12:00
Abstract:
I present a brief summary of the derivation of the Weak Gravity Conjecture within perturbative string theory, following [2403.14449], and highlight possible gaps that may hinder a fully consistent proof. I then analyze the existence and properties of the black hole solutions whose extremality bounds are compared to the string spectrum in the statement of the WGC. This analysis demonstrates that the black hole solutions we employ in our setup are reliable and do not undermine the validity of our results.

Old Journal Club: Neutrino Masses and Mixings in Gauge Models with Spontaneous Parity Violation
2025-10-30 17:00 - 18:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Pablo Blanco (IFT) will present Neutrino Masses and Mixings in Gauge Models with Spontaneous Parity Violation de Rabindra N. Mohapatra, Goran Senjanovic, Jul, 1980 Phys.Rev.D 23 (1981) 165.
Abstract:
Unified electroweak gauge theories based on the gauge group SU(2)L×SU(2)R×U(1)B−L, in which the breakdown of parity invariance is spontaneous, lead most naturally to a massive neutrino. Assuming the neutrino to be a Majorana particle, we show that smallness of its mass can be understood as a result of the observed maximality of parity violation in low-energy weak interactions. This result is shown to be independent of the number of generations and unaffected by renormalization effects. Phenomenological consequences of this model at low energies are studied. Observation of neutrinoless double-β decay will provide a crucial test of this class of models. Implications for rare decays such as μ→eγ, μ→eee¯, etc. are also noted. It is pointed out that in the realm of neutral-current phenomena, departure from the predictions of the standard model for polarized-electron-hadron scattering, forward-backward asymmetry in e+e−→μ+μ−, and neutrino interactions has a universal character and may be therefore used as a test of the model.

Top Ten Foundational Ideas of Theoretical Physics
2025-11-03 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: Anthony Zee from Kavli Institute for Theoretical Physics and the Departmentof Physics, University of California, Santa Barbara, CA, USA

Venue&Time: Red Room / 3:00 PM

Abstract:

I will list and discuss the ten foundational ideas of theoretical physics. The lecture is based on a popular book with the same title published by Princeton University Press on June 17, 2025. The book is meant to provide a sweeping overview of theoretical physics rather than a morass of details, and thus this talk may be suitable, not only for students of physics, but also for those who are interested in theoretical physics but do not know much about it.

10th IBS/IFT workshop: Dark World to the Swampland
2025-11-04 09:00 - 2025-11-07 19:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
The IBS-IFT Workshop is a regular event organized jointly by IFT and IBS-CTPU, this year reaching its tenth anniversary.
The aim of the workshop is share ideas, foster collaborations, and to discuss recent developments in theoretical physics.
The event is organized over two weeks. The first week, November 4-7, will focus on String Phenomenology
The Center for Theoretical Physics of the Universe is one of the 30 centers of the Institute of Basic Science in South Korea. The IBS-CTPU carries out research on particle physics and cosmology, which aims to understand nature at the most fundamental level and answer the big questions about the origin of the universe.
The Institute for Theoretical Physics IFT UAM-CSIC is a joint research center belonging to the Spanish National Research Council (CSIC) and the Universidad Autónoma de Madrid (UAM). It is the only Spanish center dedicated entirely to research in Theoretical Physics. The IFT members develop research in the frontiers of Elementary Particle Physics, Astroparticles, and Cosmology, in order to understand the fundamental keys of Nature and the Universe.
With this workshop we want to try to advance our understanding of quantum gravity, mainly through the swampland program, by refining several of the conjectures that have been put forth in the program to bridge the gap between effective field theories and the UV completion as quantum gravity.

HoloClub: 'N=1 Supergravity from Super Virasoro TQFT'
2025-11-04 11:30 - 13:00
Speaker: Sounak Pal (Indian Institute of Technology)
Venue&Time: Grey Room 3 / 11:30
Abstract: I will discuss some aspects of 2D and 3D quantum gravity in
the language of Topological quantum field theory (TQFT). Recent
developments include calculating various gravity partition functions
in AdS3 using descriptions of Liouville conformal field theory (CFT).
We extend this formalism for the N=1 super Liouville case and use
super-Teichmüller TQFT to compute various partition functions of
different on-shell manifolds (admitting a hyperbolic metric with
constant negative Ricci scalar). I will also touch upon some aspects
of quantum chaos and ensemble holography. I will also discuss some
possible future extensions at the end.
