Séminaire

The observation of high-energy astrophysical neutrinos by the IceCube Neutrino Observatory has opened up a new window to the universe. These neutrinos traverse the longest distances from their sources and have the largest energy ever observed. These neutrinos open a new trail to search for new physics that covers parameter space not accessible to terrestrial neutrino experiments.

Boyer Théo
Cosmological magnetic fields 

Ivanez-Ballesteros Pilar

Supernova neutrinos and nonradiative neutrino decay

Hořava-Lifshitz gravity has been proposed as a ghost-free and renormalizable quantum gravity model candidate with an anisotropic UV-scaling between space and time. In my talk I would like to present a cosmological background analysis of two different formulations of the theory, with particular focus on the running of the parameter λ with energy.

The problem of identification of ultra-high-energy cosmic ray (UHECR) sources is greatly complicated by the fact that even the highest energy cosmic rays may be deflected by tens of degrees in the galactic magnetic fields. We show that arrival directions of UHECRs from several nearest active galaxies form specific patterns in the sky, which can be effectively recognized by convolutional neural networks.

The expansion of the universe spontaneously breaks time translation by selecting a preferred reference frame. As a consequence, very much like a superfluid at zero temperature, the low-energy description of single field inflation can be organised in terms of the associated Goldstone mode of the broken symmetry (aka the phonon).

Supermassive black holes power accretion flows and outflows, and resulting radiation is observed at different wavelengths. A significant energy fraction of these flows may be carried by cosmic rays and associated high-energy non-thermal radiations. Recently, associations of high-energy neutrinos with galaxies hosting supermassive black holes, active galactic nuclei and tidal disruption events, have been reported. We review the implications of the multimessenger data for theoretical models and discuss their challenges.

 Blazars are a special type of AGN, with jets that happen to
point very close to the direction towards Earth. The powerful
gamma-ray beam from distant blazars represents a unique tool to
explore the environment along its path, and allows us to probe opacity
both inside the source and in the intergalactic medium. Internally,
gamma-rays experience attenuation due to photon-photon absorption, a
result of interactions with AGN-generated photon fields. This
interaction introduces distinct features in gamma-ray spectra. Upon