Emilio Del Giudice

QED coherence and the thermodynamics of water

It is shown that when the density becomes larger than a critical density an ensemble of water molecules evolves towards a coherent ground state, where molecules oscillate in phase with the e.m. field. At each temperature, liquid water is found to consist of a coherent phase of molecules in such a ground state and of a normal phase, whose population is determined by thermal excitations. The observed thermodynamical quantities as well as their wellknown anomalous behaviors are satisfactorily described by our theory.

ELECTRODYNAMICAL COHERENCE IN WATER: A POSSIBLE ORIGIN OF THE TETRAHEDRAL COORDINATION

In the conceptual framework of Coherent Quantum Electrodynamics we show that the molecules of the liquid phase are described by individual quantum states that differ from those in which the molecules find themselves while in the gas phase. We suggest that tetrahedral coordination emerges from such individual configurations.

Energy concentration in composite quantum systems

The spontaneous emission of photons from optical cavities and from trapped atoms has been studied extensively in the framework of quantum optics. Theoretical predictions based on the rotating wave approximation (RWA) are, in general, in very good agreement with experimental findings. However, current experiments aim at combining better and better cavities with large numbers of tightly confined atoms. Here we predict an energy concentrating mechanism in the behavior of such a composite quantum system which cannot be described by the RWA. Its result is the continuous leakage of photons through the cavity mirrors, even in the absence of external driving. We conclude with a discussion of the predicted phenomenon in the context of thermodynamics.

A Collective Approach to the Dynamics of Water

The usually neglected interaction between the electric dipole of the water molecule and the quantized electromagnetic (em) radiation field is shown to give rise to a collective (superradiant) dynamics, where two phases coexist: one in which molecules rotate coherently in phase, the other, gas-like, produced by thermal fluctuations. Such dynamics occurs in microdomains (the coherence domains) whose size is of the order of hundreds microns. Hydrogen bonding appears to be a consequence of the coherent rotation of the molecules.

Rotating wave approximation and entropy

This Letter studies composite quantum systems, like atom-cavity systems and coupled optical resonators, in the absence of external driving by resorting to methods from quantum field theory. Going beyond the rotating wave approximation, it is shown that the usually neglected counter-rotating part of the Hamiltonian relates to the entropy operator and generates an irreversible time evolution. The vacuum state of the system is shown to evolve into a generalized coherent state exhibiting entanglement of the modes in which the counter-rotating terms are expressed. Possible consequences at observational level in quantum optics experiments are currently under study.

A further look at waveguide lasers

A new approach to the dynamical evolution of a waveguide laser is presented which goes beyond the usual Maxwell-Bloch (MB) equations in that it takes fully into account the phase of the matter quantum field that describes the atomic systems. As an experimental check of its effectiveness, we analyze in its light a recent set of experiments on the effects of a dephasing of the electromagnetic laser field that find no explanation within the MB equations but, on the contrary, are in very good agreement with its expectations.