Dynamics of a Tonks-Girardeau gas released from a hard-wall trap

By using the Fermi-Bose map, we study the expansion dynamics of a Tonks-Girardeau gas released from a hard-wall trap. Exact analytical results are found for the density profile which differ from the density of a classical gas in the microcanonical ensemble for any observation time larger than a critical time associated with fermionization. Differences with the harmonic-trap case are discussed.