Instituto de Física Teórica

Seminar: 'EFTs for BSM: Counting, Ambiguities, and Application'
2026-04-09 15:00 - 16:00 (Europe/Madrid) | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘EFTs for BSM: Counting, Ambiguities, and Application’

Speaker: Shakeel Ur Rahaman (IPPP Durham).

Venue&Time: Red Room / 15:00
Abstract: The two principal frameworks for modeling the Beyond Standard Model physics as an Effective Field Theory (EFT) are the Standard Model EFT (SMEFT) and the Higgs Effective Field Theory (HEFT). SMEFT is constructed in the electroweak symmetric phase, inherently utilizing the Higgs doublet, whereas HEFT is defined in the broken phase using the physical Higgs boson alongside a separate set of Goldstone bosons. The unavoidable necessity of truncating these effective field theory expansions creates technical ambiguities that are fundamentally interwoven with the redundancies inherent in general field redefinitions. In this talk regarding HEFT, the focus will be primarily on its methodology for building operators, its power counting scheme, and the associated truncation uncertainties. These properties are already well-established within the SMEFT framework. For SMEFT, the discussion will center on its application in precision calculations and its practical implementation in Monte Carlo event generators such as Sherpa.

POSTPONED: HoloClub: 'Holographic transport in anisotropic systems'
2026-04-14 11:30 - 13:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: Holographic transport in anisotropic systems
Speaker: Claire Moran (Utrecht University)
Venue&Time: Red Room / 11:30
Abstract: Understanding transport in strongly coupled quantum systems remains a central challenge across high-energy physics, condensed matter, and quantum many-body theory. Of particular interest is systems exhibiting anisotropy, where the anisotropy leads to a much richer transport structure, with new transport coefficients emerging. The bulk viscosity becomes especially subtle in anisotropic media, where it can couple nontrivially to directional degrees of freedom and underlying microscopic structure. In this talk, I will discuss a recently developed holographic method for computing the bulk viscosity in such systems. This approach circumvents technical obstacles present in existing treatments and yields analytic expressions. I will discuss the general structure of the method, and highlight some applications of it.

Cosmology Journal Club
2026-04-14 14:00 - 15:00, 2026-04-21 14:00 - 15:00, 2026-04-28 14:00 - 15:00, 2026-05-05 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

Quantum Information Journal Club: 'Accessible quantum correlations under complexity constraints'
2026-04-15 14:30 - 15:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘Accessible quantum correlations under complexity constraints’
Speaker: Álvaro Yangüez (Sorbonne Université Paris)
Venue&Time: Gray Room 3 / 14:00
Abstract:

Quantum systems may contain underlying correlations which are inaccessible to computationally bounded observers. We capture this distinction through a framework that analyses bipartite states only using efficiently implementable quantum channels. This leads to a complexity-constrained max-divergence and a corresponding computational min-entropy. The latter quantity recovers the standard operational meaning of the conditional min-entropy: in the fully quantum case, it quantifies the largest overlap with a maximally entangled state attainable via efficient operations on the conditional subsystem. For classical-quantum states, it further reduces to the optimal guessing probability of a computationally bounded observer with access to side information. Lastly, in the absence of side information, the computational min-entropy simplifies to a computational notion of the operator norm. We then establish strong separations between the information-theoretic and complexity-constrained notions of min-entropy. For pure states, there exist highly entangled families of states with extremal min-entropy whose efficiently accessible entanglement in terms of computational min-entropy is exponentially suppressed. For mixed states, the separation is even sharper: the information-theoretic conditional min-entropy can be highly negative while the complexity-constrained quantity remains nearly maximal.

Overall, our results demonstrate that computational constraints can fundamentally limit the quantum correlations that are observable in practice.

Pheno Journal Club: Unitarity limits on triple gauge boson production
2026-04-16 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Daniel Domenech Moya (IFT) will present “Unitarity limits on triple gauge boson production”.

Venue & Time: Gray Room 2 / 12:00

Abstract:

We derive the unitarity constraints on anomalous quartic gauge couplings originating from the f ¯f ′ → V V ′V ′′ channel with V (′)(′′) = γ, Z, W ±, and H. We also assess the importance of these bounds on the present and future experimental searches.

Strings, Pheno and the Swampland (SPS) Journal Club
2026-04-16 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
Every Thursday at 12:00 in the Red Room.
Titulo: The Art of Branching: Cobordism Junctions of 10d String Theories
Speaker: Edoardo Anastasi (IFT)
Abstract: We describe the explicit construction of configurations of several 10d string theories joining at a 9d junction, providing a dynamical realization of cobordisms between multiple 10d string theories, predicted by the Cobordism Conjecture. We provide the microscopic worldsheet description of the configuration in a generalization of the `going up and down the RG flow’ interpolations recently used in the description of IIA/IIB domain wall. The interpolations involve additional degrees of freedom, which are gapped except at the branch point, at which the gap closes and triggers the branching transition. The extra degrees of freedom admit an interpretation in terms of additional dimensions in a supercritical string theory, which reduces to the 10d junction configuration upon closed tachyon condensation. Quantum corrections of the 2d worldsheet theory turn the junction into a strongly coupled lightlike core whose UV resolution lies beyond worldsheet techniques. We construct explicit examples of junctions of 10d heterotic string theories, type 0, and type II theories and orientifolds thereof. Our explicit examples include junctions of 10d chiral theories whose chiral fields flow between different branches. One particularly nice configuration is a 4-branch junction of the IIB theory, with type I, the non-supersymmetric USp(32) theory and the U(32) orientifold of 0B theory, thus assembling the four non-tachyonic descendants of type 0B theory.

Seminar: 'Symmetry TFTs for Continuous Spacetime Symmetries'
2026-04-16 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: Symmetry TFTs for Continuous Spacetime Symmetries
Speaker: Iñaki Garcia Etxebarria (Durham U.)
Venue & Time: Red Room / 3:00 PM
Abstract: I will discuss our recent proposal for the Symmetry Topological Field Theory (SymTFT) for global, continuous spacetime symmetries ( https://arxiv.org/abs/2509.07965 ). For a d-dimensional theory, it is given by a (d + 1)-dimensional BF-theory for the spacetime symmetry group, and whenever d is even, it includes also Chern-Simons couplings, that encode conformal and gravitational anomalies. This proposal is supported by the similarity to two- dimensional Jackiw-Teitelboim gravity in the d = 1 case and the topological limit of four-dimensional gravity in the d = 3 case. I will discuss how topological defects constructed from this SymTFT act by applying the associated spacetime symmetry transformation. Finally, I will discuss the relation to gravity and holography.

Seminar by Isaac Tutusaus (ICE, Barcelona)
2026-04-20 15:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: Probe combination to constrain cosmology in Euclid
Speaker: Isaac Tutusaus (ICE, Barcelona)
Venue&Time: Red Room / 15:00
Abstract: Following its successful launch in July 2023 and the start of its scientific survey in February 2024, Euclid has become the first stage-IV photometric survey in operations. In addition to its photometric observations, Euclid is also conducting a spectroscopic survey, which allows us to add even more probes to a combined analysis from Euclid data alone. In this talk I will present the forecasts for a combined analysis at the end of the mission, focusing in particular on how combining multiple probes helps break parameter degeneracies and leads to tighter constraints on the cosmological model under investigation. I will conclude by outlining current efforts toward a combined analysis with Euclid’s first data release.

Quantum Information Journal Club: 'The Quantum Agreement Theorem'
2026-04-22 11:30 - 12:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: The Quantum Agreement Theorem

Speaker: María García (upm)

Venue&Time: Gray Room 3 / 11:30

Abstract: We formulate and prove an Agreement Theorem for quantummechanics (QM), describing when two
agents, represented by separate laboratories, can or cannot maintain differing probability estimates of
a shared quantum property of interest. Building on the classical framework (Aumann, 1976), we define
the modality of “common certainty” through a hierarchy of certainty operators acting on each agent’s
Hilbert space. In the commuting case – when all measurements and event projectors commute – common
certainty leads to equality of the agents’ conditional probabilities, recovering a QM analog of the classical
theorem. By contrast, when non-commuting operators are allowed, the certainty recursion can stabilize
with different probabilities. This yields common certainty of disagreement (CCD) as a distinctive QM
phenomenon. Agreement is restored once measurement outcomes are recorded in a classical register. The
classical Agreement Theorem can therefore be seen as emergent from the quantum world via recording.
We establish an impossibility result stating that QM forbids a scenario where one agent is certain that
a property of interest occurs, and is also certain that the other agent is certain that the property does
not occur. In this sense, QM admits non-classical disagreement, but disagreement is still bounded in a
disciplined way. We argue that our analysis offers a rigorous approach to the longstanding issue of how
to understand intersubjectivity across agents in QM.

Madrid's Polygonal Gravity Seminar Series
2026-04-22 11:30 - 16:30 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Venue&Time: Red Room / 11:30 / 15:00
PROGRAM:
———————
11:00 Welcome coffee
———————
11:30h First Talk
Speaker: Jelle Hartong (Edinburgh U.)
Title: The Geometry of Gravitational Radiation
Abstract: This talk concerns asymptotically flat vacuum solutions of GR in
4 spacetime dimensions. The asymptotics of such metrics is quite intricate
and depends on how we approach infinity. If we follow null geodesics we
end up at future null infinity. This is where massless fields, including
gravitational radiation ends up. In this talk we will study the metric
near future null infinity with an emphasis on geometrical structures that
emerge in that part of the spacetime.
Future null infinity of an asymptotically flat spacetime is a conformal
Carroll manifold. I will not assume any familiarity with Carroll geometry
and explain the relevant geometrical notions as we go along. We will
consider asymptotic solutions to the 4D vacuum Einstein equations where
future null infinity is endowed with the most general Carroll metric data
that is allowed by the Einstein equations. This can be used to define an
energy-momentum tensor (EMT) at future null infinity by varying a suitably
renormalised action with respect to the boundary Carroll metric data. It
is shown that the Ward identities obeyed by this boundary EMT agree with
the Bondi loss equations that describe the loss of energy and momentum due
to the emission of gravitational waves. The metric near future null
infinity can be formulated in terms of a Cartan geometry based on the
conformal Carroll algebra. The non-vanishing curvatures of said algebra
dictate how radiative the spacetime is. For example, the vacuum degeneracy
is described by a flat conformal Carroll connection. We will see that the
Bondi loss equations can be rewritten as flux-balance laws where the
fluxes are determined by the Cartan geometry for the conformal Carroll
algebra.
——————–
15:00h Second Talk
Speaker: Eric A. Bergshoeff (U. of Groningen)
Title: Massive gravity in the lab
Abstract: In this talk I will discuss a connection between the so-called
chiral massive GMP spin-2 mode in the Fractional Quantum Hall effect and a
three-dimensional (one time and two space) relativistic massive spin-2
field in quantum field theory. In particular, I will show how the spin-2
GMP mode follows by taking a special non-relativistic limit of linearized
three-dimensional massive gravity which are the planar Fierz-Pauli
equations. I will discuss how these results can be generalized to integer
higher-spins and will present results for half-integer spins as well.
——————–
16:15 Farewell coffee
—————————————————————————–
More information about these and following monthly seminars can be found at the
webpage
https://sites.google.com/view/polygrav
We very much hope to see you there! (No registration is needed)
Fernando Barbero (IEM), Guillermo Mena (IEM), Luis Garay (UCM),
Mercedes Martin-Benito (UCM), Daniele Oriti (UCM), Tomas Ortin(IFT), Francesca
Vidotto (IEM), Eduardo Villaseñor (UC3M)

SPS Journal Club: 'Tensionless String Limits in AdS5/CFT4 and the Sharpened Distance Conjecture'
2026-04-23 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
Strings, Pheno and the Swampland (SPS) Journal Club. Every Thursday at 12:00 in the Red Room.

Title: Tensionless String Limits in AdS5/CFT4 and the Sharpened Distance Conjecture

Speaker: Gabriel Fenati (IFT)

Venue&Time: Red Room / 12:00

Abstract: Based on work in progress with M. Montero and I. Valenzuela. We extend the results of [2410.07309] by showing that all 4d Lagrangian SCFTs satisfy the bound of the Sharpened Distance Conjecture in the large N limit. We also provide an example of a quiver SCFT, dual to a stringy AdS background, where the bound is violated by taking a different kind of semi-classical limit, in which the number of gauge factors is taken to be large at fixed N.

Pheno Journal Club: 'Infinite Heat Order in 3+1 Dimensions'
2026-04-23 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Samuel Rosende (IFT) will present “Infinite Heat Order in 3+1 Dimensions”

Venue&Time: Gray Room 2 / 12:00

Abstract:

We investigate whether spontaneous symmetry breaking can persist up to arbitrarily high temperature in ultraviolet-complete quantum field theories in four spacetime dimensions. We focus on completely asymptotically free models with gauge group SU(Nc1)×SU(Nc2) and two complex scalar fields, each transforming in the fundamental representation of one gauge factor and singlet under the other. The scalar potential contains quartic self-interactions together with a negative portal coupling between the two sectors. In the Veneziano limit, this class of theories was previously shown to admit fixed-flow trajectories for which one scalar acquires a negative thermal mass at asymptotically large temperature, leading to symmetry non-restoration. Here we extend that analysis to finite numbers of colours and flavours. We derive the finite-N fixed-flow equations, compute the leading 1/N corrections to the large-N solutions, and solve the full finite-N system numerically. We find explicit finite-N benchmark theories for which the scalar potential remains bounded from below, the gauge sector is asymptotically free, and one scalar thermal mass stays negative at arbitrarily high temperature. This provides an explicit perturbative example of infinite heat order in a four-dimensional ultraviolet-complete quantum field theory with a finite field content.

Seminar by Maria Olalla Olea Romacho (King's College, London)
2026-04-23 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: ‘Traces from Primordial Magnetogenesis’

Speaker: Maria Olalla Olea Romacho (King’s College, London)

Venue&Time: Red Room / 15:00

Abstract: Magnetic fields permeate the Universe across a wide range of scales, from galaxies and clusters to the most underdense regions of the cosmic web. Gamma-ray observations of TeV blazars suggest the presence of magnetic fields in intergalactic voids, where no efficient late-time astrophysical sources exist, pointing toward a possible primordial origin and a direct link to early-Universe physics. Primordial magnetic fields arise naturally in scenarios such as inflation or cosmological phase transitions. In this seminar, I present a multi-messenger perspective on their observational signatures. On the particle physics side, I discuss collider-motivated models of electroweak phase transitions, highlighting connections to blazar observations and stochastic gravitational-wave backgrounds. On the astrophysical side, I show how primordial magnetic fields enhance small-scale structure formation, leading to dense dark matter minihalos that boost indirect detection signals, and how they impact high-redshift observables probed by the James Webb Space Telescope.

Seminar: 'Collective vortex dynamics in strongly coupled superfluids'
2026-04-27 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
Title: Collective vortex dynamics in strongly coupled superfluids
Speaker: Mikel Sanchez-Garitaonandia (University College Dublin)
Venue&Time: Red Room / 15:00

Abstract: Vorticity appears across a wide range of fluid phenomena, from the dynamics of classical fluids to quantum vortices in superfluids. In the latter case, vortices are topological defects that interact both with each other and with the surrounding medium. When a large number of vortices are present, it is natural to ask whether their collective behaviour can itself be described as a fluid, captured by an effective theory of vortex hydrodynamics. In this talk, I will explore the dynamics of many vortices in a strongly coupled superfluid with holography. By performing real-time simulations, I will investigate how the system approaches equilibrium and how its macroscopic behaviour compares with the predictions of vortex hydrodynamics. This allows to assess the range of validity of the hydrodynamic description and to understand how the system behaves beyond it.

Holo Club: (Quantum) evolution of de Sitter black holes
2026-04-28 11:30 - 12:30 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Muktajyoti Saha (ICTS-TIFR, Bengaluru)
Title: (Quantum) evolution of de Sitter black holes
Venue & Time: Blue Room / 11:30
Abstract:
I will discuss the evolution of charged black holes in asymptotically
de Sitter spacetime. These black holes evolve towards a thermal
equilibrium with the cosmological horizon. At very low temperatures
i.e. close to extremality, the semiclassical thermal description of
these black holes break down and quantum gravitational effects
dominate. Such quantum corrections can be effectively described in
terms of boundary Schwarzian modes localized at the edge of the large
near-horizon throat of these black holes. I will discuss how this
near-horizon effective theory changes the evolution of the black holes.
arXiv:2510.18035

SPS Journal Club: 'Regge trajectories for UV completions of graviton scattering from polynomial boundedness'
2026-04-30 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. Every Thursday at 12:00 in the Red Room.
Bruno Bento (IFT) will present: ‘Regge trajectories for UV completions of graviton scattering from polynomial boundedness’

Venue & Time: Red Room / 12:00

Abstract: We study graviton scattering amplitudes. Assuming they are UV completed by a theory of weakly coupled massive higher spins, we demonstrate that the UV completion must possess infinitely many Regge trajectories, and thus they are forced to have a stringy spectrum. We extend and simplify a previous proof by some of us for open-string like states to the case of external gravitons. In the present new proof, we trace the need for infinitely many trajectories to the constraint of polynomial boundedness, ultimately tied to causality. We further present numerical results based on the stringy ansatz of Häring-Zhiboedov, which illustrates how single-trajectory-like solutions actually emerge as extremal solutions of numerical bootstrap. In our numerics, these trajectories curiously show up as numerically very large textit{sister} trajectories. We provide solid evidence that the solutions are spurious as they appear to admit a divergent limit for infinite ansatz size.

Pheno Journal Club
2026-04-30 12:00 - 13:00 | Grey Room 2, Instituto de Física Teórica, Madrid, Madrid, 28037, Spain
Every Thursday at 12:00 in Grey Room 2.

Seminar: 'Quantum computing for lattice gauge theories: from the Schwinger model to an SO(3) Quantum Link model'
2026-04-30 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: Quantum computing for lattice gauge theories: from the Schwinger model to an SO(3) Quantum Link model
Speaker: Bipasha Chakraborty (University of Southampton)
Venue&Time: Red Room / 15:00
Abstract: Quantum computing provides a promising framework for simulating strongly coupled gauge theories relevant to high-energy physics. In this talk, I will discuss quantum simulations of lattice gauge theories, focusing on the Schwinger model as a benchmark Abelian system and on a non-Abelian SO(3) gauge theory formulated as a quantum link model. I will outline gauge-invariant encodings and circuit implementations suitable for near-term devices, and comment on prospects for using quantum algorithms to study real-time dynamics and other regimes challenging for classical methods.

Seminar: 'Gravitational waves from phase transitions in the early Universe: sound waves and MHD turbulence'
2026-05-04 15:00 - 16:00 | IFT Seminar Room/Red Room, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: Gravitational waves from phase transitions in the early Universe: sound waves and MHD turbulence
Speaker: Alberto Roper Pol (Geneva)
Venue&Time: Red Room / 15:00
Abstract: Gravitational waves (GWs) can be produced by a first-order phase transition in the early Universe via the fluid perturbations induced in the primordial plasma by the expansion and collision of broken-phase bubbles. I will review the production of GWs by the anisotropic stresses of velocity and magnetic fields induced in a first-order phase transition and present recent developments on the analytical estimates and numerical simulations that address the stochastic GW background produced by acoustic motion (sound waves) and magnetohydrodynamic (MHD) turbulence. These GWs could be detectable by current and future GW detectors like LISA or PTA, potentially providing us with direct clean information of the physics at the high energies of the early Universe and probing beyond the Standard Model physics. In addition, the presence of magnetic fields at a phase transition leads to coupled non-linear fluid perturbations, described by MHD turbulence, that will impact the cosmological GW background. The study of these effects can be used to put constraints on primordial magnetic fields. These fields would evolve until present time and leave observable imprints in, for example, the CMB and in the cosmic voids of the large-scale structure of the Universe, allowing us to combine GW observations with other cosmological and astrophysical observations in a multi-messenger approach.

ML-AI Journal Club: 'Machine Learning in Astroparticle Physics'
2026-05-05 11:00 - 12:00
Title: ‘Machine Learning in Astroparticle Physics’
Speaker: Daniel Nieto Castaño (IPARCOS/UCM)
Venue&Time: Gray Room 2 / 11:00
Abstract: This seminar presents the motivation for employing machine
learning (ML) techniques to mitigate some experimental limitations
within the field of astroparticle physics. We will briefly review
selected applications across various detection domains, specifically
addressing astrophysical neutrinos, cosmic rays, and dark matter
candidates. Particular emphasis will be placed upon the analysis of
very-high-energy gamma-rays, illustrating how these ML frameworks are
increasingly integral to advancing current observational capabilities.

Holo Club: Holographic transport in anisotropic systems
2026-05-05 11:30 - 13:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: Holographic transport in anisotropic systems
Speaker: Claire Moran (Utrecht University)
Venue&Time: Blue Room & Zoom / 11:30
Abstract:
Understanding transport in strongly coupled quantum systems remains a
central challenge across high-energy physics, condensed matter, and
quantum many-body theory. Of particular interest is systems exhibiting
anisotropy, where the anisotropy leads to a much richer transport
structure, with new transport coefficients emerging. The bulk
viscosity becomes especially subtle in anisotropic media, where it can
couple nontrivially to directional degrees of freedom and underlying
microscopic structure.
In this talk, I will discuss a recently developed holographic method
for computing the bulk viscosity in such systems. This approach
circumvents technical obstacles present in existing treatments and
yields analytic expressions. I will discuss the general structure of
the method, and highlight some applications of it.
Join Zoom Meeting
https://us02web.zoom.us/j/86014678323?pwd=[REDACTED]
Meeting ID: 860 1467 8323
Passcode: [REDACTED]

Seminar: 'Are string vacua connected?' by Ashoke Sen (ICTS-Infosys)
2026-05-06 11:00 - 12:00 | Blue Room, Instituto de Física Teórica (IFT) - C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Title: ‘Are string vacua connected?’

Speaker: Ashoke Sen (ICTS-Infosys)

Venue&Time: 11:00 / Blue Room

Abstract: String theory has many vacua. We shall examine the question of whether these vacua are connected from an experimentalist’s perspective.

Ashoke Sen is the ICTS-Infosys Madhava Chair Professor at the International Centre for Theoretical Sciences, Bengaluru.
His major honours include the ICTP Dirac Medal (2014), Breakthrough Prize in Fundamental Physics (2012), and the Infosys Prize in Mathematical Sciences (2009). He has also received the Padma Bhushan (2013) and the Padma Shri (2001), and is a Fellow of the Royal Society.

Quantum Information Journal Club: "Symmetry-protected topology and deconfined solitons in a multi-link Z2 gauge theory"
2026-05-06 11:30 - 12:30 | Gray Room 3, Instituto de Física Teórica (IFT) -C. Nicolás Cabrera, 13-15, Fuencarral-El Pardo, Madrid, 28049,, Spain
Speaker: Enrico Calogero Domanti

Title: “Symmetry-protected topology and deconfined solitons in a multi-link Z2 gauge theory”

Venue&Time: Gray Room 3 / 11:30

Abstract: With the advent of quantum simulators, exploring exotic collective phenomena in lattice models with local symmetries and unconventional geometries is at reach of near-term experiments. Motivated by recent progress in this direction, we study a Z2 lattice gauge theory defined on a multi-graph with links that host Z2 gauge fields. Elementary Wilson loops along pairs of these bonds allow to identify a dynamical gauge-invariant flux, responsible for Aharonov-Bohm-like interference effects in the tunneling dynamics of charged matter residing on the vertices. We find inhomogeneous phases in which an ordered pattern of the gauge fluxes spontaneously breaks translational invariance. For an even number of links, this is caused by a phenomenon of dynamical Aharonov-Bohm caging, in which particles get trapped into portions of the lattice due to destructive interference. On the other hand, an odd number of links realizes a phenomenon analogous to the Peiels instability. In this case, long-range order is shown to coexist with symmetry protected topological order, which survives the quantum fluctuations of the gauge flux induced by an external electric field. Doping the system above half filling leads to the formation of topological soliton/anti-soliton pairs interpolating between different inhomogeneous orderings of the gauge fluxes. Quasiparticles carrying fractional charge and bound at the soliton centers emerge as deconfined degrees of freedom, as they can be arbitrarily separated without feeling a confining force, in spite of the long-range attractive interactions set by the small electric field on the individual integer charges.

Shannon's Corner Journal Club: "Zeros of the partition function and their algorithmic application"
2026-05-07 11:30 - 12:30
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.
