Experimental perspectives for systems based on long-range interactions

The possibility of observing phenomena peculiar to long-range interactions, and more specifically in the so-called quasi-stationary state (QSS) regime, is investigated within the framework of two devices, namely the free-electron laser (FEL) and the collective atomic recoil laser (CARL). The QSS dynamics has been mostly studied using the Hamiltonian mean-field (HMF) toy model, demonstrating in particular the presence of first-order and second-order out-of-equilibrium phase transitions from magnetized to unmagnetized regimes. Here, we give evidence of the strong connections between the HMF model and the dynamics of the two aforementioned devices, and we discuss the perspectives for observing some specific QSS features experimentally. In particular, a dynamical analog of the phase transition is present in the FEL and in the CARL in its conservative regime. As regards the dissipative CARL, a formal link is established with the HMF model. For both FEL and CARL, calculations are performed with reference to existing experimental devices, namely the FERMI@Elettra FEL under construction at Sincrotrone Trieste (Italy) and the CARL system at LENS in Florence (Italy).