Instituto de Física Teórica

Aspects of inflation beyond the single-field, slow-roll regime
2025-09-17 10:00 - 11:30 (Europe/Madrid) | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Alejandro Pérez Rodríguez

Location&Place: Red Room

Abstract:

In this thesis, we explore two departures from the single field, slow-roll paradigm of inflation. The first part is dedicated to warm inflation. We revisit the theory of linear perturbations in this framework, develop computational techniques for the calculation of the primordial power spectrum and apply them to the analysis of CMB constraints and the production of primordial black holes. The second part focuses on the primordial non-Gaussianity arising from a phase of ultra slow-roll during single field inflation. We study the scope and limitations of the classical delta N formalism as a probe of such non-Gaussianity and determine the extent of its correspondence with the stochastic delta N formalism.
Supervisor: Guillermo Ballesteros Martínez

Dynamical Cobordism in String Theory and Holography
2025-09-16 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
Speaker: Jesús Huertas Castellanos

Institution: IFT UAM/CSIC

Location&Place: Red Room

Abstract:

This thesis investigates the intricate relationship between topology, gravity, and quantum field theory within String Theory, centering on the Cobordism Conjecture, which asserts that any consistent quantum gravity theory must allow spacetime boundaries. It begins by introducing Dynamical Cobordism through models that realize end-of-the-world branes dynamically, linking them to Swampland constraints. It then explores Bubbles of Nothing as non-perturbative instabilities, classifying them and analyzing their behavior across various theories. The third section applies Dynamical Cobordism to AdS/CFT, reinterpreting known duals in type IIB string theory as boundary-terminating geometries. Finally, it examines topological couplings and anomalies in holographic setups, introducing the SymTFT framework and uncovering new anomaly inflow mechanisms and Chern-Simons structures.
Supervisor: Ángel Uranga

Aspects of symmetries throughout the String Theory Moduli Space
2025-09-16 10:00 - 11:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Roberta Angius

Institution: IFT UAM/CSIC

Location&Place: Red Room

Abstract:

This thesis aims to explore various corners of the string theory moduli spaces using symmetries as a guiding principle to uncover properties of the corresponding theories and their implications for spacetime dynamics.

Within the Swampland Program, the absence of global symmetries in consistent quantum gravity theories is a key principle, reformulated in string theory as the Cobordism Conjecture: any consistent configuration must admit spacetime boundaries, often realized by stringy defects that trivialize cobordism charges. The first part of this thesis implements this idea in effective field theory throughDynamical Cobordism solutions, where codimension-1 end-of-the-world (ETW) branes appear as finite-distance singularities with scalars diverging to infinite field space. These provide a framework to probe infinite-distance limits in the moduli/field space and Swampland constraints. We construct explicit examples with one or multiple scalars, including networks of intersecting ETW branes, and apply them to study infinite-distance singularities in Calabi–Yau fourfold moduli spaces, described via asymptotic Hodgetheory.

On the other hand, we turn to a microscopic approach to string theory and investigate worldsheet generalized symmetries, defined by topological operators with possibly non-invertible fusion rules. In particular, we analyze the category of topological defects commuting with spectral flow and N=(4,4) superconformal symmetry in K3 sigma models. Bystudying their fusion with boundary states, we argue that while certain models admit infinitely many, or even continuous families of defects, at generic points in the K3 moduli space the category is actually trivial.

Supervisor: Ángel Uranga

Light Dark World 2025
2025-09-16 09:00 - 2025-09-19 17:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Light Dark World 2025 (LDW’25) is the tenth meeting of the annual Light Dark World International Forum, which will take place between September 16 and September 19, 2025, at the Instituto de Física Teórica (IFT) in Madrid (Spain). The workshop will gather international specialists from both experimental and theoretical backgrounds in order to examine recent progress and create new avenues for investigating the existence of light particles beyond the Standard Model, including light gauge bosons, scalars, dark matter, axions, sterile neutrinos, and dark energy fields.
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Will we know the Neutrino Mass Ordering by the end of 2026?
2025-09-15 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
The JUNO reactor neutrino experiment has recently begun collecting data, marking the start of a new precision era in neutrino research. With its unparalleled precision, JUNO is poised to refine our understanding of most neutrino oscillation parameters. Its cornerstone measurement – the determination of the neutrino mass ordering — holds the promise of a breakthrough. In this talk we will explore the physics behind the two distinct ways JUNO data can be used to probe the mass ordering, one of which could lead to the resolution of this fundamental question in the near future. Additionally, we will examine the conditions necessary for such a discovery and address potential
theoretical caveats that could influence the interpretation of the outcome.

On the Asymptotic Global Structure of Duality Frames in Quantum Gravity
2025-09-15 12:00 - 13:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Ignacio Ruiz García

Institution: IFT UAM/CSIC

Location&Place: Blue Room

Abstract:

This thesis studies the global asymptotic structure of moduli spaces in effective field theories compatible with Quantum Gravity, focusing on the Swampland Distance Conjecture. We develop taxonomy rules that determine the arrangement of towers of light states and duality frames at infinite distance, showing a finite set of possible global structures. These towers, interpreted as emergent degrees of freedom, are linked to the lowering of the EFT cut-off scale, leading to a universal relation between the leading tower and the cut-off depending only on spacetime dimension. We test these patterns in string and M-theory compactifications, recovering known constructions and suggesting new landscape corners or Swampland constraints. Finally, we explore generalizations in lower-supersymmetry settings, including non-Lorentzian decompactifications, changing fibration structures, and additional asymptotic scales, to better understand the consistency rules for EFTs admitting UV completion to Quantum Gravity.

Supervisor: Irene Valenzuela Agüí

Exploring infinite distance limits of type II Calabi–Yau compactifications
2025-09-15 10:00 - 11:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Luca Melotti

Institution: IFT UAM/CSIC

Location&Place: Blue Room

Abstract:

This thesis explores infinite distance limits in the vector multiplet moduli space of type II string theory on Calabi–Yau threefolds. First we classify such limits, identify the towers of light states, and test the Emergence Proposal, which links IR kinetic terms to loop corrections from such states. We then study the scalar curvature of the moduli space along infinite distance trajectories, focusing on cases where it diverges positively. We argue that such divergences signal decoupled field theory sectors and propose this as the only mechanism for curvature divergences in quantum gravity. Extending the analysis, we relate these limits to higher-dimensional rigid theories (5d/6d SCFTs and Little String Theories), interpreting divergences as a parametric separation between the strength of gravitational and gauge interactions. Finally, we connect curvature divergences with rigid limits and the existence of BPS states with divergent charge-to-mass ratios.

Supervisor: Fernando Marchesano

Entangle This VI: 100 years of quantum
2025-09-15 09:00 - 2025-09-19 20:00 | Parque del Retiro, Plaza Murillo, 2,, Madrid, 28014,, Spain
As part of the International Year of Quantum Science and Technology, the workshop Entangle This VI will bring together experts at the forefront of quantum theory and experiment. It is organized by the Quantum groups at IFT and IFF.
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Holographic thermal entropy and modular conjugation from geodesic bit threads
2025-09-09 11:30 - 13:30
Speaker: Francesco Gentile

Institution: SISSA

Location&Place: Grey Room 2

Abstract:

In this talk, I will discuss some new interesting properties of geodesic bit threads in static backgrounds.
Bit threads are an insightful tool for investigating holographic entanglement entropy, providing a reformulation of the Ryu-Takayanagi formula in terms of the maximal flux of a bounded and divergenceless vector field.
An explicit realization of bit threads is given by geodesic bit threads.
I will first argue that, for a spherical region on AdS boundary and for an interval on the BTZ boundary, geodesic bit threads display a surprising connection with modular conjugation in CFT.
Then, I will show that for an interval on the BTZ boundary and for a spherical region on the boundary of Schwarzschild AdS, the flux of geodesic bit threads hitting the event horizon provides the holographic thermal entropy, i.e. the product of a thermal entropy density with the volume of the spherical region.

Dark Matter Clues from the Faintest Galaxies
2025-09-08 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: Julio Navarro

Institution: University of Victoria

Abstract: Lambda Cold Dark Matter (LCDM) is the most successful theory for the formation of structure in the Universe. Although its predictions have been verified on large scales, they are still contested on the scale of dwarf galaxies, whose dynamical properties are often cited as evidence for the need to revise some of LCDM’s basic tenets. In this context, I will discuss the recent discovery of the faintest galaxies known to date, and how their properties may be used to place constraints on the clustering of dark matter on the smallest galactic and sub-galactic scales, as well as on the viability of some of the proposed alternatives to LCDM.

Cosmological Constraints from Simulation-Based Forward-Modeling of DES Cluster Abundances
2025-06-26 15:00 - 16:15 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Cluster cosmology is potentially one of the most powerful observational probes of structure formation. However, enabling unbiased cosmological constraints requires careful modeling of the cluster selection function. In the case of optical cluster cosmology, this requires accurate modeling of projection effects. We will introduce a new simulation-based inference framework with which we reanalyze DES Y1 cluster abundances, highlight both the promise and challenges of this new approach.

Novelties in flavour physics
2025-06-23 15:00 - 16:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
I will give a brief overview of the so called flavor anomalies, describing the main strategies followed to disclose physics beyond the Standard Model. I will focus on selected modes and observables that can help identifying the nature of new physics.

New Insights in Black Hole Physics from Holography
2025-06-16 09:00 - 18:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Black holes serve as natural laboratories for probing gravity under extreme conditions. New Insights in Black Hole Physics from Holography, hosted at the Instituto de Física Teórica UAM/CSIC in Madrid, will bring together leading researchers to discuss recent advances in black hole physics through the framework of holography. The workshop will cover a range of topics, including quantum aspects of black holes, near-extremal black hole dynamics, probes of singularities and interior reconstruction, holographic applications to strongly correlated systems, and modern developments in quasinormal modes and black hole perturbations. Featuring distinguished speakers and fostering new collaborations, this event aims to advance our understanding of black holes and their dual descriptions in quantum field theory, offering new insights into fundamental questions in quantum gravity.
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Complexity in Krylov basis at extreme scenarios
2025-06-12 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
In recent times quantum computational complexity has been a major interest to both QI and HEP communities. Complexity in the Krylov basis is one such candidate which has proved its worth in several setups by providing us with meaningful insights.

Strong lensing cosmology and the line of sight
2025-06-10 14:00 - 15:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Strong gravitational lensing is a powerful observational tool in astrophysics and cosmology which has been used to study the mass and light properties of galaxies and quasars the scales and distributions of dark matter subhaloes and the expansion history of the Universe.

Exclusive or inclusive? The lattice might have the answer...
2025-06-09 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
The elements of the CKM matrix are fundamental parameters of the Standard Model. Substantial experimental and theory efforts are under way aimed at determining them ever more precisely and accurately.

The fluctuating spacetime of dark matter
2025-06-05 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
What if dark matter only interacts with the visible sector through gravity?

SYK wormholes out of equilibrium
2025-06-02 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
In 2 dimensions holographic duality gives the possibility of studying quantum gravity in terms of the dual SYK quantum mechanical theory. A particularly capturing model involves two coupled SYK systems.

Holographic description of the Nieh-Yan anomaly
2025-05-29 15:00 - 16:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Holographic description of the Nieh-Yan anomaly.

Probing low-reheating scenarios with freeze-in dark matter
2025-05-26 15:00 - 16:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
The feebly-interacting massive particle (FIMP) paradigm offers an intriguing solution to the dark matter (DM) puzzle with FIMPs produced via the freeze-in mechanism due to extremely weak interactions with the standard model (SM) plasma.

Understanding thermalization in a non-Abelian gauge theory
2025-05-22 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
Understanding the mechanism of thermalization in gauge theories is one of the challenging problems of contemporary research.

Bootstrapping line defects in AdS3/CFT2
2025-05-20 15:00 - 16:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
We study correlators of insertions along 1/2 BPS line defects in the holographic dual to type IIB string theory in AdS3×S3×T4 with mixed Ramond-Ramond and Neveu Schwarz-Neveu Schwarz three-form flux.

Generalized Symmetries Branes and Holography
2025-05-19 15:00 - 16:15 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
The notion of global symmetry in quantum field theory has been generalized in many interesting directions including p-form symmetries higher-form symmetries and non-invertible symmetries.

Bootstrapping CFTs with moduli spaces
2025-05-13 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
Many SUSY CFTs have a continuous space of vacua known as a moduli space. Understanding how moduli spaces manifest in CFT data is crucial for classifying and constraining SUSY CFTs yet remains an open problem.

Unraveling the DAMA/LIBRA Puzzle: last results from the ANAIS-112 Experiment
2025-05-12 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
For over two decades the DAMA/LIBRA experiment has reported an annual modulation in the low-energy region consistent with the expectation from dark matter (DM) in the galactic halo due to Earth’s motion around the Sun.

Bubble wall velocity from hydrodynamics
2025-05-08 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
Terminal velocity reached by bubble walls in cosmological first-order phase transitions is an important parameter determining both primordial gravitational wave spectrum and the production of baryon asymmetry in models of electroweak baryogenesis.

Extra dimensions of space: science or fiction?
2025-05-05 15:00 - 16:15 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
In this (hopefully) pedagogical talk I explain why it is useful to contemplate extra dimensions of space and how it can change the way we think about the cosmological constant problem.

Continuous spin particles on-shell
2025-04-28 15:00 - 16:15 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Continuous spin particles (CSPs) arise naturally in the classification of unitarity representations of the Poincaré group but have long been dismissed because of their unintuitive nature.

Hadronic resonances from Lattice QCD
2025-04-24 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
The majority of known hadrons in the low-energy QCD spectrum are resonances observed in multi-particle scattering processes.

Gravitational Particle Production and Leptogenesis
2025-04-10 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
In a curved spacetime the definition of particles depends on the observer’s frame of reference.
