Winter Meeting 2026

2 Feb 2026, 09:00 → 3 Feb 2026, 18:00 Europe/Madrid

Aula Magna Enric Casassas (Facultat de Física)

WELCOME!

The ICCUB Winter Meeting 2026 edition!

This year, the meeting will take place on February 2nd-3rd 2026. As you know, the idea of this meeting is to gather in person as many people from the ICCUB as possible, and give the opportunity to young researchers working in the research areas of our Institute (Astrophysics, Particle Physics, Cosmology, Gravitation and Nuclear Physics) to provide to a broad audience didactic and entertaining reviews of the fields in which their research is embedded. There will be also interesting talks on the status of the technological part of the institute. PhDs, postdocs and some seniors, all ICCUB members and collaborators, will be invited to give a talk on their topics of interest. The meeting will also offer an opportunity to the participants with different interests to meet and discuss their research activities with other scientists working outside their specialty, but within the broad scope of ICCUB study areas.

The workshop will be held at the Facultat de Física in the Universitat de Barcelona. The format will consist of 6 talks in the morning and 6 in the afternoon during the two days. Each talk will last 25 minutes, and there will be programmed coffee breaks in between to foster interaction. Speakers are strongly encouraged to give their talks at a Physics graduate student level, and with a strong outreach tone, to make the talks easy to follow for ICCUB members working in very different fields.

Everybody is invited to participate in this event.

We are sure you will enjoy it!

Formulari d'inscripció. Informació detallada_en_Winter_Meeting.pdf

Monday 2 February

1 Welcome

2 The trichotomy of Primordial Black Holes initial conditions

In this talk, I will show that the formation of primordial black holes, in an asymptotically flat and radiation dominated Friedman-Robertson-Walker (FRW) Universe, is not mainly determined by the behaviour of the smoothed linear over-density at its maximum, as earlier thought, but also by the three-dimensional curvature at smaller (but super-horizon) scales, which is called “the core”. I will present three classes of initial condition characterised by an open, closed or flat FRW core. I will motivate the use of the three-dimensional curvature as the key parameter to determine the threshold of PBH formation.

Speaker: Laia Montellà (ICCUB)

3 Nuclear equation of state: from the Lab to the Stars

The nuclear equation of state (EoS) at zero temperature (T) can be expressed as the energy (E) per particle (A) or pressure (P=–∂E/∂V for A=constant) of an uniform system of neutrons and protons in their ground state. This ideal system is of particular interest for different reasons: i) Coulomb and finite-size effects are avoided (by construction) making comparisons among different models easier; ii) sound methods exist to solve the nuclear many-body problem in this limit; iii) neutrons and protons away from the surface of the nucleus approximately behave as those of the uniform system (saturation density); or iv) neutron star outer core is thought to be made of neutrons and few protons in β–equilibrium with electrons and muons; among others.

The properties of this ideal system can be studied from laboratory data and inferred from Neutron Star observations only via nuclear models. Most nuclear models are based on two pillars: the Hamiltonian and a sound many-body method. While accurate and systematically improvable many-body methods exist, this is not exactly the case of the nuclear effective Hamiltonian that has not been fully characterised yet.

In this short introductory presentation I will focus on some selected examples that allow us to learn about the nuclear EoS from experiments and observations.

Speaker: Prof. Xavier Roca Maza (University of Barcelona and University of Milan)

11:15 Coffee break

4 Late Reheating scenarios: How low can we really go?

Modern, ground and space based observatories have provided us with a wide range of observations from different epochs of the Universe. Despite these efforts, the Universe before Big Bang Nucleosynthesis (BBN) remains obscure to us. Then, the measurements of the primordial abundances of light elements are key when exploring theories for the early Universe. In this talk, I will discuss the phenomenology of reheating scenarios around neutrino decoupling and the formation of primordial elements. In such cases, we parametrize the reheating with a new particle called $X$ that is set to decay just before the start of BBN. The presence and posterior decay of such particle modifies the expansion history of the Universe as well as the neutrino thermalization, up until the freeze-out of the weak rates. I will explain what is our approach to these scenarios and why previous constraints on reheating temperatures are sometimes not as robust as we think. In the end, I will also mention the next steps to make the most general and consistent bounds on the reheating temperature.

Speaker: Pau Carles Llorca (Institut de Ciències del Cosmos (ICCUB))

5 A fast code for the evolution of tidally limited star clusters and their binary black hole mergers

Star clusters play a key role in shaping the population of compact-object binaries observed through gravitational waves, but modeling their long-term evolution across a wide range of initial conditions remains computationally challenging. Fast and physically motivated models are therefore essential.

I will present an updated version of the clusterBHBdynamics code, a rapid framework for evolving star clusters containing stars and stellar-mass black holes. The new version improves the treatment of tidal mass loss, incorporates the effects of metallicity and stellar mass function variations, and introduces a revised gravitational-wave module. In particular, it includes prescriptions for gravitational-wave captures during dynamical interactions and for inspirals triggered by eccentricity growth between encounters.

The model is calibrated against a large set of Cluster Monte Carlo and direct $N$-body simulations spanning a broad range of cluster masses, sizes, metallicities, and Galactic environments. With the calibrated parameters, the code reproduces the global evolution of clusters and their black hole populations to within ~15%, and predicts binary black hole merger rates consistent with numerical simulations at the ~20% level. Owing to its sub-second runtime per cluster, clusterBHBdynamics enables efficient exploration of star cluster populations and their contribution to gravitational-wave sources.

Speaker: Fotios Fronimos Pouliasis (ICCUB)

13:00 Lunch break

6 The PhotSat mission: Ultraviolet and visible all-sky monitoring with a CubeSat

PhotSat is the first astrophysical satellite developed from design to operations by the Institute of Space Studies of Catalonia (IEEC) and the Catalan industrial ecosystem. The main scientific goal of the mission is to obtain a full sky photometric monitoring of the approximately 40 million brighter astrophysical sources down to magnitude 15, performing studies of transients, exoplanets, solar system bodies, stars, galaxies, etc. By using a cubesat platform in low-Earth orbit, PhotSat will be able to access both the optical and ultraviolet ranges using two independent telescopes. Thanks to their wide field of view (8 degrees) the mission will be able to revisit each sky position with a cadence of only 2-3 days during the design lifetime of 2-3 years. PhotSat will provide dense light curves for all bright sources in the sky, simultaneously in three different passbands (one in the ultraviolet and two in the optical) using CMOS detectors. The PhotSat consortium is composed of several institutes, universities and industries in the Catalan ecosystem. In this sense, PhotSat is also helping to establish new collaborations and develop the joint capability of executing science experiments from their initial stages, including preliminary design, construction, launch, and operations; using off-the-shelf NewSpace technologies.

Speaker: Josep Manel Carrasco Martínez (Institut d'Estudis Espacials de Catalunya)

7 Neutron Star Glitches in Dipolar Supersolids

Glitches in neutron stars are sudden increases in their rotational frequency and are believed to originate from the stochastic unpinning of quantized vortices stored in their interior [1]. While previous studies explored this mechanism using externally imposed pinning potentials [2], dipolar atoms in the supersolid phase offer a distinct advantage: their intrinsic density modulation naturally provide the required pinning forces required for vortex trapping [3]. In this talk, I will employ dipolar supersolids as platform to explore vortex dynamics related to a glitch signal. By tuning the strength of the isotropic interaction, we investigate more accurately the dynamics of vortices across different phases ( e.g. uniform-modulated superfluid), mimicking different radial depths of the star.
[1] A. Melatos et al 2008 ApJ 672 1103 (2008)
[2] Mon. Not. R. Astron. Soc. 415, 1611–1630 (2011)
[3] Phys. Rev. Lett. 131, 223401 (2023)

Speaker: Héctor Briongos-Merino (University of Barcelona)

8 Estimating the Rates of Stellar Mergers in the Milky Way from Astrophysical Transients

Luminous Red Novae (LRNe) are astrophysical transients thought to arise from stellar mergers, offering an important insight into the final stages of binary evolution. To date, only four Galactic LRNe have been identified, with the most recent detected in 2008, making it difficult to constrain their intrinsic rate in the Milky Way. In this PhD project, I investigate how detections from current time-domain surveys can be used to estimate the Galactic stellar merger rate by simulating the detectability of LRNe. I develop an injection-and-recovery simulation framework in which synthetic LRNe light curves are generated using templates of known Galactic LRNe (V4332 Sgr, V838 Mon, and V1309 Sco) and placed at random locations throughout the Milky Way, assuming they trace the stellar mass distribution of the disk and bulge. These simulated events are scaled for distance and interstellar extinction using three-dimensional dust maps and are then sampled through the actual cadence and sensitivity of the Zwicky Transient Facility (ZTF). By quantifying the fraction of injected LRNe that would be recovered by ZTF, I determine the detection efficiency for different types of Galactic stellar mergers. I will discuss the main challenges of this approach and present current progress, including searches for candidate events in real-time alert streams.

Speaker: Grace Katusiime (ICCUB)

15:45 Coffee break

9 Inflation without an inflaton

The inflationary paradigm successfully explains the observed large-scale homogeneity and isotropy of the Universe, while also providing a mechanism for generating the seeds necessary for the formation of cosmic structures. In the simplest models, the nearly scale-invariant and almost Gaussian primordial perturbations arise from the amplification of quantum vacuum fluctuations of the scalar inflaton field, whose microphysical origin and the structure of its potential remain unknown.
Motivated by the search for a model-independent description of inflationary dynamics, I will discuss a novel scenario in which inflation is produced without relying on a scalar field. In the ‘inflation without inflaton’ framework, the inflationary expansion is driven by a de Sitter background and scalar fluctuations arise as second-order effects from tensor metric perturbations (i.e. gravitational waves).
I will outline the theoretical framework, present the prediction for the scalar power spectrum and discuss the new advances in the study of its intrinsic primordial non-Gaussianity.

Speaker: Marisol Traforetti (ICCUB)

10 Quantum science with cold atoms at ICCUB

Cold neutral atoms constitute a highly controllable platform for studying complex quantum phenomena as well as for developing quantum technology. Some examples of their applications include atomic clocks, quantum computation and simulation, and the testing of fundamental physics. In recent years, the detection and manipulation of atoms at the individual level have pushed forward many directions in the field. A major example can be found in quantum-gas microscopes, which enable the direct characterization of strongly correlated quantum many-body systems.

In this talk, I will begin by giving an introduction to the field of cold atoms, discussing concepts like laser cooling and optical trapping. I will then focus on their use as quantum simulators, based on some of my previous experimental research works. In the final part of the talk, I will present the first steps toward establishing the first cold-atom experiment at the Universitat de Barcelona.

Speaker: Antonio Rubio-Abadal (UB, ICCUB)

11 The Nuclear Bridge to New Physics: Theoretical challenges in $0\nu\beta\beta$

The exploration of physics Beyond the Standard Model within nuclear physics is closely tied to the investigation of rare electroweak transitions. The most promising process correspond to the neutrinoless double-beta decay ($0\nu\beta\beta$) which is a transition in nuclei where two neutrons simultaneously transform into two protons, accompanied by the emission of only two electrons [1]. This second-order decay, if observed, would prove that neutrinos are Majorana particles (their own antiparticles), shed light on the existence of massive neutrinos, and help explain the predominance of matter over antimatter in the universe. Understanding this kind of process would unveil important features on neutrino physics, astrophysics and cosmology.
The half-lives depend on the square of the nuclear matrix elements (NMEs), which must be computed since $0\nu\beta\beta$ has not been observed yet.

In this talk, I will present the framework used to compute NMEs and discuss their crucial role in the search for $0\nu\beta\beta$. I will then address higher-order corrections to the NMEs within the nuclear shell model (NSM) and the quasiparticle random-phase approximation (QRPA) frameworks [2]. These calculations aim to reduce the theoretical uncertainties associated with NMEs. Finally, I will briefly present new predictions for two-neutrino double-beta ($2\nu\beta\beta$) transition half-lives, from the $0^+$ ground state to the first $0^+$ excited state, and discuss their connection to $0\nu\beta\beta$ decay. These results incorporate novel higher-order contributions at the NME level [3,4].

M. Agostini et al. Rev. Mod. Phys. 95, 025002 (2023)
L. Jokiniemi, D. Castillo, P. Soriano, J. Menéndez, Phys. Lett. B 860, 139181 (2025).
D. Castillo, D. Frycz, B. Benavente, J. Menéndez, arXiv:2507.21868
S. el Morabit et al. JHEP 06, 082 (2025)

Speaker: Daniel Castillo Garcia (University of Barcelona/ICCUB)

Tuesday 3 February

12 Radial-dependence model of simulated Solar Energetic Electrons

Solar activity, such as flares and Coronal Mass Ejections (CMEs), can accelerate protons, electrons and ions up to relativistic speeds causing Solar Energetic Particle (SEP) Events. These events can have a big role in the amount of radiation received by a spacecraft, astronaut missions or even high altitude flights. They can even afect Earth’s navigation systems or cause communication blackouts when a SEP event is strong enough to produce a Ground Level Enhancement (GLE).
The effect of SEP events thoughout the whole heliosphere is just being unveiled by the Solar Orbiter (SolO) and Parker Solar Probe (PSP) missions, but is far from being well characterized. Using state-of-the-art models (PARADISE and EUHFORIA) we simulated the transport of electrons in the interplanetary medium to obtain radial distance dependences of their intensities and fluences.
In this brief and introductory presentation I will explain some of the physics underlying the transport of electrons in the inner heliosphere as well as discuss some of our findings.

Speaker: Roger Prat (Universitat de Barcelona)

13 Dark Matter in a Left-Right Symmetric Model

We investigate dark matter phenomenology in a left-right symmetric model based on an (SU(3)_c \times SU(2)_L \times SU(2)R \times U(1){B-L}) gauge theory with a softly broken parity symmetry. The model naturally contains light neutral fermion and scalar states that serve as viable dark matter candidates, with masses ranging down to the GeV scale. The interactions of dark matter are predominantly governed by couplings to left- or right-handed neutrinos, leading to distinct phenomenological features. We analyze the relic abundance, relevant constraints, and detection prospects of these dark matter candidates using several representative benchmark parameter sets, and identify viable regions of parameter space consistent with current experimental bounds.

Speaker: keyun wu (ICCUB)

14 Gravitational signals from symmetry breaking

Symmetries, and their breaking, are a cornerstone of our understanding of particle physics. Consequently they have been probed intensively at colliders. However, if the breaking of a symmetry occurs at scales much larger than the energy reached in colliders, then it remains elusive. In this talk I will present an alternative method to study the breaking of particle physics symmetry by exploiting the gravitational wave remnants from the very early universe. In fact, the phase transitions breaking a symmetry can typically proceed via two distinct channels: a sharp and discontinuous first order transition or a smoother cross-over. The firts case generates gravitational wave via the expansion of the nucleated bubbles while the second case produce gravitational wave via the formation of topological defects like cosmic strings or domain walls.

Speaker: Miguel Vanvlasselaer (ICCUB)

11:15 Coffee break

15 ICCUB Advanced Technology Unit (software & data division): present, future and synergies of the Gaia catalogue

The ICCUB Advanced Technology Unit (ATU) is contributing to the software development and data processing of several projects of the Institute, including PLATO, PhotSat, LISA, and especially Gaia, as well as its proposed successor (GaiaNIR). In the first part of this talk, I will do the usual recap of software & data activities being carried out by the ATU team. Afterwards, I will focus on the current status of Gaia, for which we are intensively working on its fourth data release (planned for December this year). As an appetizer of its contents, publication approach and envisaged tools for the community, and to showcase its possible synergies, I will present one of our recent developments - the GJDR3Plus catalogue, joining Gaia DR3 and J-PLUS DR3 data into a single, convenient table downloadable as Parquet files. This synergetic catalogue provides astrometry and exquisite multi-band photometry for galactic and extra-galactic sources. An experimental on-line service with notebooks and a fast database is also available, the capabilities of which will be shown in this talk.

Speaker: Dr Jordi Portell de Mora (ICCUB)

13:00 Lunch break

16 Chronicles of regular black holes: the higher-curvature saga

As shown by Hawking and Penrose, black holes in general relativity are doomed to contain a singularity in their interior, where even the notion of space-time breaks down. This is no longer the case for regular black holes, for which no singularities appear. In this talk, I will explain how regular black holes arise naturally as exact solutions of theories of gravity including an infinite tower of higher-curvature corrections. I will also discuss how these regular black holes are formed through dynamical collapse of matter.

Speaker: Ángel Jesús Murcia Gil (ICCUB)

17 From molecular clouds to stellar associations

Understanding how molecular clouds collapse and disperse to form stars and planets is a key question in astronomy. In this talk, I will review several complementary lines of research aimed at uncovering the origin of young star clusters and OB associations in the solar neighborhood. I will discuss how the large number of substellar objects–brown dwarfs and free-floating planets–recently detected in nearby star-forming regions can constrain the formation of these objects. I will also present how the spatial distribution, kinematics, and ages of OB associations trace the propagation of star formation and the dispersal of their parent molecular clouds.

Speaker: Núria Miret Roig (Universitat de Barcelona)

18 Rethinking Resonance Detectability during Binary Neutron Star Inspiral: Accurate Mismatch Computations for Low-lying Dynamical Tides

Tidal forces excite oscillatory modes of a neutron star in a binary system as the inspiral sweeps through the mode's resonant frequency. The excitation of the oscillatory modes imprints frequency-dependent signatures on the emitted gravitational waveform. These manifest as a sudden phase change in the waveform and an advance in the merger time of up to a millisecond or so.
In this talk we quantify when such resonant effects become observable by current and next-generation gravitational wave observatories. We compare waveforms with and without a resonance to assess the detectability of these effects, and explore the possibility of identifying resonant signatures from previously observed binary neutron star events.

Speaker: Alberto Revilla (Institut de Ciències del Cosmos Universitat de Barcelona (ICCUB))

15:45 Coffee break

16:10 Musical minutes

19 Unveiling the earliest stages of massive star formation through interferometric radio observations

The formation of stars with masses greater than 8 times the mass of the Sun still remains unclear. Recently born massive stars are deeply embedded in the most crowded and densest regions of the interstellar medium of galaxies; thus, they are highly obscured to optical and even infrared wavelengths. Therefore, interferometric radio observations are crucial to shedding light on the formation mechanism of massive stars. In this talk I will summarize the results of the analysis of the radio emission from massive star-forming regions observed with high angular resolution, aiming to probe the closest vicinity of massive stars at their earliest stages (i.e., down to Solar System scales). At these scales, essential elements associated with the evolution of protostars like putative disks, companions, ionized inflows or jets can be explored. I will focus on the emblematic example IRAS 18162-2048: an extremely young 20 Msun star that powers the longest and fastest protostellar radio jet known in our Galaxy. We conducted a multi-epoch study of the radio emission originating at the heart of this jet inferring processes that might occur at a few tens of AU, making this IRAS 18162-2048 one of the best case studies on the mechanism of mass growth in massive stars during their earliest stages.

Speaker: Josep Maria Masqué (ICCUB)

20 Lepton Flavour Universality tests with b-baryon decays at the LHCb experiment

Rare $b\to s \ell\ell$ transitions are strongly suppressed in the Standard Model (SM), making them sensitive to physics beyond the SM. Leptons from the different families have the same coupling to electroweak bosons in the SM, symmetry that is known as Lepton Flavour Universality (LFU). Precise measurements of LFU ratios in $b\to s \ell\ell$ decays provide, then, a very powerful null test of the SM. $R_{pK}$ was the first LFU test involving b-baryons published by LHCb, which studies the decay $\mathit{\Lambda}_b^0\to pK^–\ell^+\ell^−$ using Run 1 and 2016 data and yielded a compatible result with the SM within 1 standard deviation significance, as well as the first observation of the $\mathit{\Lambda}_b^0 \to pK^–e^+e^–$ decay. The new $R_{pK}$ analysis includes full dataset (adds 2017-18 data), a full re-optimisation of the selection after the observation of the electronic decay, with particular focus on the MVA and particle identification requirements. Additionally, the measurement splitted in low and central $q^2$ regions will be provided. The preliminary results show a clear improvement of the statistical uncertainty (16% to 9.5%) with a better control of the backgrounds.

Speaker: Albert López Huertas (Universitat de Barcelona)

21 Cosmological simulations of the Local Group as a test of the Cold Dark Matter Model

The standard model of cosmology is the best cosmological model that explains the nature and evolution of the Universe. Over the last decades, cosmological computer simulations have proven to be a very useful tool to test cosmological models such CDM and our Local Group is the perfect laboratory to confront these results with high precision observations. In this work, we performed cosmological simulations of the Local Group using the public program Gadget and our own initial conditions created from specific primordial overdensity fields. The main goal is to obtain specific initial conditions that fit the recent 6-D phase-space observations of our Local Group (including distances and proper motions), and to study the dynamical history of the principal galaxies to test they arise from the growing mode in CDM.

Speaker: Adrián Santander Garrote (ICCUB)