Shannon's Corner Journal Club: "Zeros of the partition function and their algorithmic application"
2026-05-07 11:30 - 12:30 (Europe/Madrid)
Speaker: Aram Harrow (MIT)
Title: “Zeros of the partition function and their algorithmic application”
Venue&Time: Gray Room 1 / 11:30
Abstract: “At high temperatures quantum systems generally lose
long-range order. We would expect that this makes them easier to
simulate. One way to understand this is through the analytic
properties of the partition function. Viewing Z(beta) = tr e^{-beta
H} as a function of a complex beta, its zeros turn out to tell us both
about phase transitions and about classical algorithms for estimating
Z(beta).”

SPS Journal Club: 'Calibration, fuzziness: new results on AdS vacuum decay'
2026-05-07 11:30 - 12:30
Strings, Pheno and the Swampland (SPS) Journal Club

Speaker: Vincent Menet (Università Milano Bicocca)

Title: ‘Calibration, fuzziness: new results on AdS vacuum decay’

Venue&Time: Red Room / 11:30

Abstract: Motivated by swampland conjectures, we study the stability of AdS type II supergravity vacua. In the literature, vacuum decay mediated by abelian D-branes has been discussed extensively, while this isn’t quite the case for both the D-brane bound states, and their non-abelian counterparts. In this context, we first present a tool to study large classes of D-branes and bound states, based on calibration theory, and then discuss vacuum decay mediated by weakly non-abelian D-branes. We illustrate our results by applying them to a few concrete AdS vacua.

Pheno Journal Club: "On the Inverse Problem in Effective Field Theory"
2026-05-07 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Jaime Fernandez Tejedor (IFT) will present “On the Inverse Problem in Effective Field Theory”.

Venue&Time: Gray Room 2 / 12:00

Abstract:

We show that the tree-level spectrum of heavy particles can be directly extracted from the Wilson coefficients of the corresponding effective field theory at low energies. This procedure is exact when the number of resonances is finite, and otherwise approximate. Our results are derived from a new class of analytic dispersion relations that depend nonlinearly on the scattering amplitude and apply to an exceedingly broad class of theories and kinematics.

Seminar by Christian Northe (Institute of Physics, Prague)
2026-05-07 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: Entanglement through topological interfaces in CFT revisited
Speaker: Christian Northe (Institute of Physics, Prague)
Venue&Time: Red Room / 15:00
Abstract: Present theoretical predictions for the entanglement entropy through topological defects are violated in numerical simulations of critical systems. In this talk, I discuss a paradigm shift in the preparation of reduced density matrices in the presence of topological defects, and emphasize the role of defect networks with which they can be dressed. Grouplike and duality defects are considered in detail for the Ising model, establishing agreement with all numerically found entanglement entropies. Since this new construction functions at the level of reduced density matrices, it accounts for topological defects beyond the entanglement entropy to other entanglement measures. The framework employs boundary conformal field theory techniques to implement the factorization of Hilbert space, which I recapitulate at the beginning of the talk and discuss its relation with the entanglement spectrum.

Seminar: 'Primordial Black Holes -- Positivist Perspective, Quantum Quiddity and Galaxy Genesis'
2026-05-11 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: ‘Primordial Black Holes — Positivist Perspective, Quantum Quiddity and Galaxy Genesis’
Speaker: Florian Kühnel, (TU Dortmund & LMU Munich)
Venue&Time: Red Room / 15:00
Abstract: Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes those black holes recently discovered through gravitational waves, and (part of) these may conceivably be of primordial origin. After a general introduction on primordial black holes, I review the observational hints for their existence — from a variety of lensing, dynamical, accretion and gravitational-wave effects. As I will show, all of these (over 20) may be explained by a single and simple unified model, naturally shaped by the thermal history of the Universe. If time permits, I discuss how recent advances in our understanding of quantum effects in black holes impact PBHs. This prominently concerns deviations from Hawking radiation in the form of the memory-burden effect. Finally, I will elucidate on the role primordial black holes have on early galaxy and star formation.

Holo-Club: 'Emergence of Closed Universes in Holography'
2026-05-12 11:30 - 12:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Martin Sasieta (U. Berkeley)
Title: ‘Emergence of Closed Universes in Holography’
Venue&Time: Gray Room 3 / 11:30
Abstract:
I will present recent constructions of closed universes in AdS/CFT and AdS2 holography, and discuss some of the puzzles they pose.

Cosmology Journal Club
2026-05-12 14:00 - 15:00, 2026-05-19 14:00 - 15:00, 2026-05-26 14:00 - 15:00, 2026-06-02 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

DIFT Colloquium by Benjamin Grinstein (University of California, San Diego)
2026-05-13 15:30 - 16:00 | IFT Auditorium, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, Madrid, 28049,, Spain
Title: Buckets versus pipes: the neutron lifetime puzzle

Speaker: Benjamin Grinstein, University of California, San Diego

Date and time: 15:30h (CEST), Wednesday, May 13, 2026

Location: CFTMAT Auditorium

Abstract: A precise knowledge of the neutron lifetime is important because it serves as a fundamental input for Big Bang Nucleosynthesis (BBN) models, which predict the primordial abundances of light elements. It also enters in the determination of the Cabibbo mixing angle, crucial in testing the validity of the CKM theory of quark flavor, in understanding reactor neutrino detection rates and the behavior of matter in extreme environments like neutron stars. Precise experiments give very precise results, but the values determined differ by over 1% with high statistical significance depending on the technology used for the experiment. In this talk I will review this so-called “neutron lifetime puzzle” and some of the proposed solutions.

Join Zoom Meeting:
https://us02web.zoom.us/j/83038393323?pwd=[REDACTED]
Meeting ID: 830 3839 3323
Passcode: [REDACTED]
This event 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 lines: Origin and composition of the universe: Astroparticles and Cosmology (Astro/Cosmo) & Particle Physics in the Standard Model and Beyond (BSM).

SPS Journal Club: 'Type IIB at Eight Derivatives: A Status Report'
2026-05-14 11:30 - 13:30 | 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 (SPS) Journal Club
Title: ‘Type IIB at Eight Derivatives: A Status Report’
Speaker: Raffaele Savelli (Dipartimento di Fisica & INFN, Università di Roma “Tor Vergata”)
Venue&Time: Red Room / 11:30
Abstract:
Knowledge of ten-dimensional superstring effective actions beyond the leading order in the derivative expansion is of intrinsic interest and plays a central role in many questions in string phenomenology. For Type IIB string theory, all the effective couplings are known at the four-point level, but a complete characterization of the eight-derivative effective action remains elusive.
In this seminar, I will discuss recent progress in deriving the five-point contact terms in sectors that mix gravity with the three-form flux and the axio-dilaton. I will present different approaches to this problem and emphasize the role of SL(2,Z) duality in constraining the structure of eight-derivative couplings and in revealing universal kinematical patterns. Finally, I will briefly comment on applications to lower-dimensional physics.
The talk is based on arXiv:2205.11530 and arXiv:2507.07934.

Seminar: 'Perturbative aspect of electroweak phase transitions in the Early Universe'
2026-05-14 12:00 - 13:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘Perturbative aspect of electroweak phase transitions in the Early Universe’

Speaker: Andrii Dashko (DESY)

Venue&Time: Blue Room / 12:00

Abstract: We present a study of the perturbative description of thermally driven electroweak phase transitions (EWPT) in the early universe. Focusing on strong first-order transitions, which are relevant for gravitational wave cosmology, we examine the dimensional reduction as a tool for a precise and systematic description focusing on the running of effective parameters within the effective field theory (EFT), and the impact of higher-dimensional operators. This allows us to assess the range of validity and theoretical uncertainties of the EFT approach. We demonstrate these results with applications to the Standard Model Effective Field Theory (SMEFT) and singlet extensions of the Standard Model, both of which can realize strong EWPT.

Pheno Journal Club
2026-05-14 12:00 - 13:00
Every Thursday at 12:00 in Grey Room 2.

Seminar: 'On the evidence for elastic interactions in the dark sector'
2026-05-18 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: ‘On the evidence for elastic interactions in the dark sector’
Speaker: Jose Beltrán Jiménez, University of Salamanca.
Venue & Time: Red Room / 15:00
Abstract: The increasing quality of cosmological data has revealed > some tensions among different probes that could be signalling the necessity of incorporating new physics into our cosmological model. One particularly intriguing possibility is the existence of elastic interactions between dark matter and dark energy. Not only do these interactions provide a natural mechanism to relief cosmological tensions, but there is also compelling observational evidence for them, to the extent that a detection could even be claimed. I wil review the potential of these scenarios in relation to the cosmological tensions and discuss distinctive signatures that can be probed with future data, thus providing a smoking gun for these interactions.

Quantum Information Journal Club: 'Optimal strategies for near-term simulation of fermionic systems with scalable local fermion-to-qubit mappings'
2026-05-20 11:30 - 12:30
Title: ‘Optimal strategies for near-term simulation of fermionic systems with scalable local fermion-to-qubit mappings’

Speaker: Manuel G. Algaba

Venue&Time: Gray Room 3 / 11:30

Abstract: Quantum simulation of interacting fermions remains one of the most compelling applications of quantum computing, but its practical realization depends on more than the asymptotic promise of fault-tolerant quantum algorithms. To bridge the gap with current NISQ devices, we derive a strategy for growing the corresponding code distance of local fermion-to-qubit mappings, which is otherwise fixed. Building upon the extended error detection properties of these mappings we present a quantum error mitigation (QEM) technique tailored for fermionic systems which outperforms other widely used techniques such as Post-selection, Virtual Distillation, and Probabilistic Error Cancellation in regimes of practical interest. We then study the performance of different combinations of QEM and fermion-to-qubit mappings and identify the best combination of mapping and QEM. This study enables us to derive minimal hardware requirements for the simulation of Fermi-Hubbard models of various sizes in near-term devices.

Pheno Journal Club
2026-05-21 12:00 - 13:00, 2026-05-28 12:00 - 13:00, 2026-06-04 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain

SPS Journal Club: 'Generalised anomalies, QCD, and holography'
2026-05-21 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
Title: ‘Generalised anomalies, QCD, and holography’
Speaker: Mohammad Akhond (Dipartimento di Fisica & INFN, Università di Roma “Tor Vergata”)
Venue & Time: Red Room / 12:00
Abstract: During the last decade, the notion of an ‘t Hooft anomaly has been generalised to the case of discrete symmetries. An interesting instance, discussed by Tanizaki, is the mixed anomaly between the discrete axial symmetry and the flavour and baryonic symmetries in massless QCD. The goal of this talk is to provide a derivation of this anomaly from a top-down holographic dual of QCD. I will show that the topological couplings in the bulk supergravity dual of the D4-D8 system encode Tanizaki’s anomaly, once fluctuations around the bulk gauge fields are turned on. A technical challenge for this computation is the difficulty in maintaining gauge invariance of supergravity theories in the presence of D-branes. To overcome this issue, a compact formulation of the flux sector of (massive) type IIA supergravity in the presence of D8 branes is presented.

Seminar: 'Exploring Effective Theories of Gauged Chiral Symmetries at the LHC and Beyond'
2026-05-21 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: Exploring Effective Theories of Gauged Chiral Symmetries at the LHC and Beyond
Speaker: Felix Yu (Mainz U.)
Venue & Time: Red Room / 15:00
Abstract: I discuss theoretical issues with constructing effective theories of gauged chiral symmetries, taking a quark-universal U(1)_B symmetry as an example. I will review the phenomenology of the Z-Z’-photon vertex and point out novelties regarding a non-renormalization theorem and connections to electroweak loop calculations and dimensional regularization. I also present the collider signatures from the exotic scalar sector and the characteristic nature of non-decoupling chiral matter.

Seminar: 'Weak Particles with a strong impact'
2026-05-25 15:00 - 16:00
Title: ‘Weak Particles with a strong impact’
Speaker: Aritra Gupta (Krea University, India)
Venue&Time: Red Room / 15:00
Abstract: Dark matter and neutrinos are among the most elusive particles in nature, yet they play a central role in the evolution of the Universe. Their extremely weak interactions make them difficult to detect, but also allow them to probe environments inaccessible to ordinary matter.
In this colloquium, I will discuss how astrophysical systems and neutrino observatories can be used to explore the physics of dark matter and neutrinos beyond the Standard Model. I will present scenarios where dark matter and neutrino physics are intimately connected, leading to observable consequences in cosmology and astroparticle experiments. I will also discuss how dark matter accumulated inside compact stellar environments can significantly modify supernova cooling along with other detectable indirect signatures. Throughout the talk, I will highlight how compact stars, neutrino detectors, and astrophysical observations together provide new windows into the dark sector.

SPS Journal Club: Heterotic Ouroboros
2026-05-28 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 (SPS) Journal Club

Title: Heterotic Ouroboros

Speaker: Chiara Altavista (IFT)

Venue&Time: Red Room / 12:00

Abstract: M-theory on {mathbf{S}}^1vee{mathbf{S}}^1 has recently been proposed to yield, via quotients, ten-dimensional non-supersymmetric string theories. We revisit the construction that leads to the heterotic theories, finding a consistent set of rules that reproduces the light spectra and gauge groups, including indications of their global structure. Our approach uses the gauge enhancement mechanism of type I’ string theory, applied to a setting in which the type I’ interval is curled onto itself, with its two boundaries separated by a branch cut. Using these tools, we reproduce the ten-dimensional heterotic theories and provide some evidence for junctions among them.

Seminar by Marco Finetti (U. Aveiro)
2026-05-28 15:00 - 16:00
Title: ‘First Order Phase Transitions and Gravitational Waves’
Venue&Time: Red Room / 15:00
Speaker: Marco Finetti (U. Aveiro)
Abstract: The Laser Interferometer Space Antenna (LISA) will be the first space-based gravitational wave (GW) detector, opening a new observational window for both astrophysics and early-Universe cosmology. Operating in the millihertz band, it will probe a rich superposition of GW signals. Astrophysical population models predict a sufficient number of signals in the LISA band to blend together and form an irresolvable Galactic foreground noise. In addition, a stochastic gravitational wave background (SGWB) of cosmological origin could add an unknown component to the measured noise. In this talk, I will assess the bias induced on the parameter estimation of stochastic signals, arising from the unresolved binaries buried within the cosmological signal. Using a representative SGWB model, I will quantify the impact of this effect on the reconstruction of the foreground template parameters and, most importantly, on those of the SGWB model itself. Neglecting inter-template correlations can lead to significan biases, and, for several benchmark cases, those biases exceed the statistical reconstruction uncertainties. These findings expose a key limitation of existing template-based strategies and indicate that unbiased component separation will likely require additional information, such as constraints from resolved sources obtained through global-fit analyses.

Seminar: 'Classical Krylov probes and chaotic semiclassical strings'
2026-06-01 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
Title: ‘Classical Krylov probes and chaotic semiclassical strings’
Speaker: Saskia Demulder (CUNEF)
Venue&Time: Red Room / 15:00
Abstract: Quantum chaos is a central theme in string theory, but classical chaos is also a generic feature of semiclassical string dynamics. Motivated by the need to explore the broad landscape of non-integrable string dynamics, I will introduce a classical version of Krylov complexity and related diagnostics using the Koopman-von Neumann formulation of classical mechanics. I will then explain how this framework can be applied to integrability-breaking deformations of otherwise integrable semiclassical string solutions. In particular, I will show how such deformations induce characteristic redistributions of spectral weight, leading to observable-dependent delocalisation and spreading in Koopman-Krylov space. This talk is based on [2602.23421] and ongoing work, both in collaboration with Rathindra N. Das.

Holo-Club: From Volume as a Clock to Boundary Dynamics in JT Gravity
2026-06-02 11:30 - 13:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: From Volume as a Clock to Boundary Dynamics in JT Gravity
Speaker: Farbod-Sayyed Rassouli (University of Nottingham)
Venue&Time: 11:30 / Blue Room
Abstract:
Different notions of time arise from different choices of observer. In cosmological settings, a particularly natural choice is the spacetime volume, which is conjugate to the cosmological constant. This leads to a notion of unimodular time that deparametrizes the Wheeler–DeWitt equation into a Schrödinger-like evolution equation, while also inducing a natural time variable at the boundary. In this talk, I will first explain how this construction arises in arbitrary dimension, with particular emphasis on the 4D case. I will then turn to Jackiw–Teitelboim gravity, where promoting the vacuum cosmological constant to a dynamical top-form degree of freedom provides a bulk clock in the Henneaux–Teitelboim sense. On the boundary, this modifies the usual Schwarzian dynamics by coupling it to an additional U(1) phase mode, reproducing the universal low-energy structure familiar from complex SYK. I will show how the corresponding boundary theory can itself be rewritten as a (0+1)-dimensional observer action, making explicit the relation between the bulk volume clock and its holographic boundary counterpart.
arXiv:2601.07911

A diffuse flux of MeV ALPs
2026-06-02 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
Title: ‘A diffuse flux of MeV ALPs’
Speaker: Marina Cermeño
Venue&Time: Red Room / 15:00
Abstract: MeV scale axion-like particles can be produced with semi-relativistic velocities in Galactic supernovae, leading to a diffuse flux that can be detectable in neutrino water-Cherenkov detectors (Super + HyperK). In this talk, I will explain the details of the calculation that we recently did in 2602.17597 also with some content from our previous works 2412.09595 , 2412.19890)

Quantum Information Journal Club: 'Polynomial-time thermalization and Gibbs sampling from system-bath couplings'
2026-06-03 11:30 - 12:30
Title: ‘Polynomial-time thermalization and Gibbs sampling from system-bath couplings’

Speaker: Sam Slezak (ENS Lyon)

Venue&Time: Gray Room 3 / 11:30

Abstract: Many physical phenomena, including thermalization in open quantum systems and quantum Gibbs sampling, are modeled by Lindbladians approximating a system weakly coupled to a bath. Understanding the convergence speed of these Lindbladians to their steady states is crucial for bounding algorithmic runtimes and thermalization timescales. We study two such families of processes: one characterizing a repeated-interaction Gibbs sampling algorithm, and another modeling open many-body quantum thermalization. We prove that both converge in polynomial time for several non-commuting systems, including high-temperature local lattices, weakly interacting fermions, and 1D spin chains. These results demonstrate that simple dissipative quantum algorithms can prepare complex Gibbs states and that Lindblad dynamics accurately capture thermal relaxation. Our proofs rely on a novel technical result that extrapolates spectral gap lower bounds from quasi-local Lindbladians to the non-local generators governing these dynamics.

IFT Colloquium: Matthew Headrick (Brandeis & IHES)
2026-06-03 15:00 - 16:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Venue&Time: Blue Room / 15:00
Coffee will be served in the cafeteria at 16:15h
Title: ‘Black holes, quantum entanglement, and the geometry of spacetime’
Speaker: Matthew Headrick (Brandeis & IHES)
Abstract: Black holes are by far the most entropic objects in the universe, and their enormous entropy directly connects the macroscopic world governed by general relativity to the Planck scale governed by quantum gravity. It turns out that they are just a piece of a much larger and richer story, hinting that, despite the notorious difficulty of quantizing gravity, quantum mechanics and general relativity are actually two sides of the same coin. I’ll explain these connections, and along the way try to answer the question: Is Newton’s constant really equal to 1?

SPS Journal Club: 'Sharpened Dynamical Cobordism'
2026-06-04 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
Strings, Pheno and the Swampland (SPS) Journal Club

Title: Sharpened Dynamical Cobordism

Speaker: Alejandro Javier Puga Gómez (IFT)

Venue&Time: Red Room / 12:00

Abstract: We propose a sharpened version of Dynamical Cobordism, where the physical structure ξ of the theory in question determines an allowed range Rξ for the critical exponent δ. We interpret a singularity with δ∈Rξ as a true transition-to-nothing, i.e., a configuration ending spacetime, while a singularity with δ∉Rξ indicates some obstruction to such a transition, i.e., the presence of a non-trivial cobordism global charge, which is incompatible with a theory of quantum gravity. In the spirit of the original Cobordism Conjecture, this apparent inconsistency of the theory can be alleviated via the modification of the structure, for instance by introducing new degrees of freedom and associated defects. Inspired by the Gubser criterion for good singularities, we propose a way to determine Rξ. As a proof-of-concept we show explicitly how the introduction of a higher-form gauge field changes the allowed range of δ compared to an EFT with only scalars. We test this sharpened version of Dynamical Cobordism against several examples, such as massive IIA string theory, where it is notably compatible with the presence of O8-planes; the Janis-Newman-Winicour and Garfinkle-Horowitz-Strominger black hole solutions; and certain singular distributions of D-branes. In all these cases, the Sharpened Dynamical Cobordism Conjecture leads to results consistent with our expectations.
