Multimessenger Imprints of Heavy Nuclei in High-Energy Neutrino Sources

• Pasquale Serpico (LAPTh, CNRS & Université Savoie Mont Blanc)

The joint observation of astrophysical sources in gamma rays and neutrinos can provide invaluable insight into the physical conditions of the source, including its size, particle densities, and acceleration and production mechanisms. I will present results of a recent investigation of the role of the (typically neglected) nuclear composition in high-energy astrophysical environments, obtained via Monte Carlo simulations of nuclear and electromagnetic cascades within the source. The imprints of the injected composition on the resulting neutrino and gamma-ray emissions will be presented, with the specific case of NGC 1068 used as benchmark. I will also mention the importance of MeV gamma-ray observations for constraining the source composition in the context of future gamma-ray experiments, as supported by a dedicated re-analysis of archival COMPTEL observations.

Primordial black holes — Small scales, big problems

• Sam Young (University of Pisa)

Primordial black holes (PBHs) provide a unique window into the small-scale primordial perturbations that are otherwise difficult to probe observationally. In this talk, I will discuss how PBHs can be used to constrain the primordial power spectrum, focusing on the connection between the abundance of PBHs and the statistics of the underlying density fluctuations. I will also highlight some of the theoretical uncertainties and conceptual challenges involved in calculating the PBH abundance, and discuss ongoing efforts to understand and improve these calculations. Finally, I will discuss the importance of developing a robust theoretical framework for PBHs and their associated gravitational-wave signals in preparation for upcoming gravitational-wave detectors.

Latest Results from the Dark Energy Spectroscopic Instrument (DESI): Is the Standard Cosmological Model in Question?

• Davide Bianchi (University of Milan)

The Dark Energy Spectroscopic Instrument (DESI) has produced the most extensive three-dimensional map of the Universe to date, precisely measuring the positions of millions of galaxies and quasars. The evolution of this map across cosmic space and time reflects the interplay among ordinary matter, neutrinos, dark matter, and dark energy. Intriguingly, when DESI’s results are combined with other cosmological observations, tensions with the standard cosmological model emerge that are not yet fully understood. A simple extension in which the dark energy equation of state evolves over time appears to provide a better fit to the observations. I will present these recent DESI results and discuss their implications for cosmology, as well as the prospects for future measurements.

Preparing for the first strongly lensed supernova discoveries with the Rubin Observatory

• Nikki Arendse (SMASH Fellow, University of Nova Gorica)

When a supernova explodes behind a massive galaxy, its light can be gravitationally lensed into multiple images. Such a strongly lensed supernova is a rare and powerful probe that provides insights into distant supernova explosions, dark matter in galaxies, and even the expansion rate of the Universe. While only a handful of lensed supernovae have been discovered to date, the Legacy Survey of Space and Time (LSST) at the Vera Rubin Observatory is expected to discover orders of magnitude more. On June 29th, after years of anticipation, LSST began full survey operations. I will share our efforts in the LSST Science Collaborations towards finding the first strongly lensed supernovae — such as cross-matching with Euclid lenses, testing the alert pipeline, and generating a large, realistic training set for machine learning classifiers. I will also present results from a transformer-based tool I am developing to recommend optimal photometric follow-up observations for lensed supernovae.