High-Energy Neutrinos: A New Trail Towards New Physics

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.

Searches for long-duration transient signals in ground-based gravitational-wave detectors

Over the past 8 years, Advanced LIGO and Advanced Virgo have detected about 90 gravitational-wave (GW) events, all of them produced by the coalescence of a compact binary system (CBC). In addition to CBCs, new types of GW signals are expected to be observed in the near future, as the sensitivity and observing time of GW detectors increase. Among them, we refer to long-duration transients as GW signals whose duration in the frequency band of the detectors ranges from few seconds to hours.

Cosmological Phonon Collider

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). Similar to particle colliders, if we were to scatter sound waves, the presence of additional heavy fields coupled to the medium would manifest as distinct peaks in the cross-section of the phonons.

High-Energy Multimesssenger Emission from Supermassive Black Holes

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.

Searching for Internal Absorption Signatures and Probing EBL Using Gamma-Rays from High-Redshift Blazars

 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


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