High-energy gamma rays as probes of fundamental physics and cosmology

by Rafael Alves Batista (Sorbonne University)

Thursday 20 Jun 2024, 15:00 → 16:30 Europe/Berlin

seminar room 3 (bldg. 1b)

The propagation of gamma rays across vast distances serves as a valuable tool for probing both fundamental physics and the intergalactic medium. As high-energy gamma rays travel towards Earth, they can interact with pervasive photon fields, producing electron-positron pairs that subsequently upscatter background photons to high energies, initiating an electromagnetic cascade. This process is highly sensitive to the properties of the medium, such as the distribution of infrared and optical photons comprising the extragalactic background light (EBL), and the characteristics of intergalactic magnetic fields (IGMFs).
At high energies, gamma-ray propagation serves as an exceptional tool for investigating low-energy manifestations of quantum gravity effects, such as Lorentz invariance violation (LIV). Additionally, gamma rays can interact with axion-like particles (ALPs), a candidate for dark matter. This noteworthy bi-directional relationship allows us to use gamma rays to probe non-standard phenomena, thereby expanding our toolkit for dark matter detection and for probing fundamental physics.
In this presentation, I will first review the phenomenology of gamma-ray propagation, discussing it within the context of various astrophysical environments. I will then briefly touch upon how gamma rays can be used to probe IGMFs. Finally, I will discuss the prospects for detecting ALPs through astrophysical gamma-ray observations.