The mission of the BEC Center

The aim of the Center on Bose-Einstein Condensation (BEC) is to promote research on the various phenomena related to Bose-Einstein condensation and to the physics of cold atomic gases in traps. Since the first observation of BEC in cold gases in 1995, the study of ultracold gases has become an emerging area of research at the crossing point of several disciplines, including atomic, molecular and optical (AMO) physics, statistical mechanics and condensed matter physics.

Interest in BEC derives from several factors. BEC is the only known phase transition taking place also in the absence of interactions, its origin being purely quantum mechanical. Thus it is one of the cornerstones of quantum statistical mechanics. Before 1995 BEC had only been explored in strongly interacting systems, such as superfluid helium, where the effects of the interaction mask some crucial features of BEC. The dilute gas experiments of the past years have made it possible to compare in a systematic way experimental data with the predictions of first principle theory. The theoretical approaches have been mainly based, in the first years, on the use of Gross-Pitaevskii theory for the order parameter and have proven quite successful, especially to predict the behaviour of these systems at low temperature, both at equilibrium and out of equilibrium. Together with the rapid progress of experimental investigations, new themes emerged in the theoretical side. These include, among others, the dynamics of the condensate at finite temperature, the kinetic phenomena in the presence of BEC, the nucleation of quantized vortices, the dynamics of vortex arrays, the nature of the phase transition for reduced dimensionalities and in the presence of array geometries, the emergence of new quantum phases, like number squeezed and Schroedinger cat states, the occurrence of new topological structures in multicomponent condensates, the behaviour of BEC for large scattering lengths and the role of Feshbach resonances, the occurrence of chaos in the dynamics of BEC, the fluctuations of the condensate for small samples, the theory of the order parameter beyond mean field, the mechanisms of decoherence of the phase, the stability of solitons and vortex rings. The remarkable property exhibited by BEC of generating a macroscopic population of atoms in the same quantum state has also opened up the new field of coherent manipulation of matter waves, with interesting implications for precision spectroscopy, frequency standards, atomic gyroscope, atom lithography and holography, sensors, etcetera.

In the last few years an impressive activity in the field of ultracold gases has also concerned the study of Fermi gases. Despite the initial difficulty in cooling such systems experimentalists have been quite successful in obtaining highly degenerate samples, providing new concrete perspectives in the study of Fermi superfluidity, including the long sought BCS-BEC crossover. At present Bose-Einstein condensation of molecules (pairs of fermions) has been succefully achieved and new challenging experimental and theoretical perspectives are characterizing the international scene. Other hot topics concern ultracold gases of atoms with long-range dipolar interaction, gases of dipolar molecules, and a variety of proposals to use ultracold atoms in optical lattices as quantum simulators, for the search of novel quantum phases.

The growth of the BEC field has crucially benefited by the cooperative efforts of experimental and theoretical groups in many laboratories. The aim of the BEC Center is to reinforce the interdisciplinary links of the theoretical research. On the other hand the Center is intended to reinforce the scientific collaborations between theoretical and experimental activities, establishing direct and systematic links with the main laboratories in the world.