By: J. Tito Mendonca
From: IPFN and CFIF, Instituto Superior Tecnico, Lisboa
At: Complexo Interdisciplinar, Anfiteatro
We discuss the basic concepts of photon angular momentum (POAM), and describe the main theoretical and experimental results. We then consider the exchange of angular momentum between a photon beam and a plasma vortex, and demonstrate the possible excitation of POAM states in a plasma. We also discuss the role of POAM in nonlinear wave mixing, and focus on the exchange of angular momentum between electromagnetic and electrostatic waves in a plasma, due to the stimulated Raman and Brillouin backscattering processes. This could be relevant for plasma diagnostics, both in laboratory and in space. Finally, we extend the POAM concept to neutrinos. Coupling between different OAM electron-neutrino states in the presence of a dense plasma is considered. We show that plasma vorticity can be transferred to neutrino beams, which could be relevant to the understanding of neutrino sources in astrophysics. Observation of neutrino OAM states could eventually become possible.