Despite the astounding successes of the SM, there are several reasons why the Standard Model of strong and electroweak interactions cannot be the ultimate theory of particle interactions, both experimental and theoretical character. Among them, the nature of dark matter, the origin of neutrino masses, the inclusion of gravity and black holes, the origins of the matter-antimatter asymmetry and the flavor structure of the SM, the electroweak naturalness and the strong CP problems. This has motivated the development of theories beyond the Standard Model (BSM), which is the main task of the BSM subgroup of the IFAE Theory Group, and the experimental search of BSM physics, which in particular is being undertaken at the LHC.
The group consists of UAB Profs. Alex Pomarol, Eduard Massó, Clara Murgui and Fabrizio Rompineve, ICREA Research Professors Diego Blas and Andrea Wulzer, IFAE researchers Oriol Pujolas and former ICREA Research Professor Mariano Quirós, now IFAE Emeritus Professor as well as postdocs Ricardo Z. Ferreira, Mario Herrero-Valea, Evangelos Sfakianakis, Teng Ma, Juan Sebastian Valbuena Bermúdez and Ricardo Vicente, George Zahariade and Ziyu Dong. The group activities are mainly in Beyond the Standard Model, Astro-Particle and Cosmology.
The detection of high-frequency gravitational waves (HFGWs) represents the next frontier in the intersection of fundamental physics, astrophysics and metrology. Since the first detection of gravitational waves by LIGO in 2015, scientists have been able to probe the universe in the frequency range from 10 Hz to 10 kHz. However, vast unexplored bands remain, including the MHz to GHz range. Contrary to their lower-frequency counterparts, these bands are characterized by extremely weak backgrounds from known objects, which makes them a perfect messenger of the unknown Universe, in particular of sources connected to some of the most fundamental questions of modern Cosmology: dark matter, inflation or quantum gravity.
In March 2025, a team of scientists led by ICREA Prof. Diego Blas, Instituto de Física de Altas Energías, Spain, Prof. Dr. Matthias Schott, Rheinische Friedrich-Wilhelms-University, Bonn, Germany, Prof. Dr. Dmitry Budker, Johannes Gutenberg University, Mainz, Germany, and Dr. Claudio Gatti, National Institute for Nuclear Physics, Italy, funded GravNet: A Global Network for the Search for High-Frequency Gravitational Waves, the first worldwide network of detectors aiming at developing and deploying a novel experimental platform to detect HFGWs.
GravNet will be initially funded by an ERC-SYNERGY grant (awarded in 2024) and is based on an innovative use of quantum sensing technologies. The project utilizes cavities in strong magnetic fields to convert gravitational waves into photons. To maximize the chances of detection, GravNet will deploy a network of detectors across multiple European laboratories: Bonn, Mainz, Frascati and PSI. These detectors will be synchronized using a GPS-based data acquisition scheme, enabling them to function as a unified, highly sensitive array.
This network is being joined by other institutes worldwide, with the first joint data-taking campaigns expected in 2026. By launching a novel detection program that bridges gravitational wave science with cutting-edge quantum sensing technologies, GravNet will foster collaboration and synergies between these two scientific communities to detect the first traces of the hidden Universe.
In collaboration with Profs. A. Ghoshal (U. of Warsaw), E. Megías (U. of Granada) and G. Nardini (U. of Stavanger) I have initiated a deep study on complementary experimental probes of warped extra dimensions at present and future facilities. We first studied the formation of primordial black holes (PBHs) and stochastic gravitational waves background (SGWB) produced by the supercooled radion phase transition (PT) in warped models solving the gauge hierarchy problem.
We first determine how the SGWB and the produced PBH mass and abundance depend on the warped model’s infrared energy scale ρ, and the number of holographic colors N . With this finding, we recast on the plane {ρ, N } the current SGWB and PBH constraints, as well as the expected parameter reaches of GW detectors, as LISA and ET, and the gravitational lensing ones, such as NGRST. We also map the collider bounds on massive graviton production, and cosmological bounds on the radion phenomenology.
In the range ρ ≃ (0.05 − 0.5) GeV, we can explain the recent SGWB hint at nHz frequencies and generate PBH binaries with mass MPBH ∼ (0.1 − 1)M⊙ detectable at LISA and ET. The experimentally allowed mass region where PBHs can account for the whole dark matter abundance, corresponds to 10 TeV ≲ ρ ≲ 104 TeV. Such a region represents a great science case where forthcoming and future colliders like HE-LHC and FCC-hh, gravitational-wave observatories and other PBHs probes play a key complementary role.
We obtained the spectrum of GWs from domain walls (shown on the right plot below), crucially including their annihilation phase (that is required for observational viability). The result was obtained using state-of-the-art cosmological lattice field theory simulations (a snapshot of which is shown in the left plot). The result is of interest for searches of new physics in GW datasets, such as those from Pulsar Timing Arrays and ground-based interferometers (currently working with the local LVK group on a search in the O4 dataset).
We opened an unexplored avenue for fundamental physics exploration exploiting a possible future muon collider. Specifically, we show that flavor-breaking interactions due to heavy new physics can be probed at a 10 TeV muon collider in the high-energy production of quarks and leptons. The high collision energy mitigates the suppression of the new interactions, offering sensitivity to interaction scales well above 100 TeV both in the lepton and in the quark sector. This offers a novel strategy for flavor physics exploration that is independent, complementary and in some cases strongly superior to the traditional approach based on low-energy probes.
Using bootstrap techniques based on imposing fundamental principles such as Lorentz invariance, positivity, locality, analyticity and crossing symmetry, we have resolved the last remaining case in the classification of consistent higher spin effective field theories (EFTs). We showed that an effective field theory for a single massive spin 3/2 particle is only viable in the presence of gravity. Furthermore, the case of two massive spin 3/2 particles also requires the presence of a photon.