  The low energy behaviour of the isotropic t--J ladder system is investigated
using exact diagonalization techniques, specifically finding the Drude weight,
the charge velocity and the compressibility. By applying the ideas of Luttinger
liquid theory, we determine the correlation exponent $K_\rho$ which defines the
behaviour of the long range correlations in the system. The boundary to phase
separation is determined and a phase diagram is presented. At low electron
density, a Tomonaga-Luttinger-like phase is stabilized whilst at higher
electron densities a gapped phase with power law pairing correlations is
stabilized: A large region of this gapped phase is found to exhibit dominant
superconducting correlations.
