Causal interpretation of Fermi fields

C. Compagno, C. M. Palma, Roberto Passante +1 more

Nicola Cufaro Petroni, Anastasios Kyprianidis, Z. Marić +2 more

P. N. Kaloyerou

Erez Zohar, Benni Reznik

The Fermi two-atom problem illustrates an apparent causality violation in quantum field theory that has to do with the nature of the built-in correlations in the vacuum. It has been a constant subject of theoretical debate and discussion in the last few decades. Nevertheless, although the issues at hand could in principle be tested experimentally, the smallness of such apparent violations of causality in quantum electrodynamics have prevented the observation of the predicted effect. In this paper, we show that the problem can be simulated within the framework of discrete systems that can be manifested, for instance, by trapped atoms in optical lattices or trapped ions. Unlike the original continuum case, the causal structure is no longer sharp. Nevertheless, as we show, it is possible to distinguish between ‘trivial’ effects due to ‘direct’ causality violations and the effects associated with Fermi's problem, even in such discrete settings. The ability to control externally the strength of the atom–field interactions enables us also to study both the original Fermi problem with ‘bare atoms’ and correction in the scenario that involves ‘dressed’ atoms. Finally, we show that, in principle, the Fermi effect can be detected using trapped ions.

Jordi Cat

The 'microcausality' condition in quantum field theory is typically resented and justified on the basis of general principles of physical causality. I explore in detail a number of alternative causal interpretations of this condition. I conclude that none is fully satisfactory, independent of further and controversial assumptions about the object and scope of quantum field theories. In particular the stronger causal readings require a fully reductionist and fundamentalist attitude to quantum field theory. I argue, in a deflationary spirit, for a reading of the 'microcausality' condition as mere boundary condition, inspired by Relativity, that different possible formulations of quantum field theory must obey

G. Compagno, G. Massimo Palma, Roberto Passante +1 more