One way of detecting or constraining Lorentz invariance violation (LIV) effects is by measuring time delays in the arrival of very high-energy (VHE) photons from astrophysical sources. Suitable targets are variable, distant and highly energetic objects such as pulsars, gamma-ray bursts (GRBs), and active galactic nuclei (AGN) flares. However, a major challenge arises from intrinsic time lags...
In this talk I will discuss the general phenomenological features of Lorentz Invariance Violation (LIV) and Doubly Special Relativity (DSR) frameworks. Particular attention will be given to anomalies in the flux of very-high-energy (VHE) and ultra-high-energy (UHE) gamma rays from astrophysical sources, arising from modifications of interaction thresholds induced in LIV and DSR scenarios. Such...
Lorentz Invariance Violation (LIV) effects are predicted in some theories of Quantum Gravity (QG) and would manifest as energy-dependent modifications to particle kinematics. Such effects can alter the threshold of the electron–positron pair production process, leading to observable deviations in the absorption of very-high-energy photons by the Extragalactic Background Light (EBL). We exploit...
When using the light curves of rapid blazar flares for searches of propagation effects, it is important to understand the
intrinsic temporal and spectral signatures introduced by the underlying particle acceleration and emission processes
producing those flares. Unfortunately, the nature of these processes is not well known. Most scenarios place the emission
region inside the relativistic...
High-energy cosmic neutrinos probe fundamental physics at scales of energy and distance otherwise unreachable, where new physics may manifest. Since the discovery of TeV-PeV cosmic neutrinos in 2013, we have explored this progressively more broadly and more precisely, thanks to a growing number of detected neutrinos and improvements in reconstruction and analysis techniques. Quantum gravity...
Searching for new phenomena predicted by quantum-gravity (QG) effects in high-energy astrophysics implies to be able to distinguish the signatures related to standard physics in sources and propagation from the ones coming from pure QG. In this contribution I will focus on the interpretation of ultra-high-energy cosmic ray (UHECR) data in terms of astrophysical scenarios for the fluxes of...
Multiwavelength and multimessenger observations, combining data across the electromagnetic spectrum with high-energy neutrinos, provide a uniquely powerful probe of the physical processes at work in the relativistic jets of blazars. Recent campaigns and coincident neutrino detections have reinforced the role of blazars as prime laboratories for studying particle acceleration and radiation in...
What if there are already signatures of quantum gravity (QG) in the existing high-energy multi-messenger data -- would we be able to know that?
In this talk, I discuss the complexities inherent in separating new physics from conventional astrophysical processes. Disentangling these two signals is not merely a technical challenge; it is an epistemic one. I argue that we are currently limited...