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We have treated the ground state of the positronium negative ion (Ps-) by a hrperspherical harmonica expansion method in which the centre of mass motion is properly accounted for. The resulting system of coupled differential equations has been solved by the renormalized Numerov method. We find that the convergence in the Binding Energy (BE) with respect to inclusion of higher hyperspherical partial waves is quite slow for this diffuse system. Using our exact numerical results up to a maximum of 28 for the hyper angular momentum quantum number (KJ in an extrapolation formula basd on the hyperspherical convergence theorems, we get the binding energy of the ground state of Psas 0.261 668 9 au.

This paper is devoted to the evaluation of the pionic scalar density at finite temperature and baryonic density. We express the latter effect in terms of the nuclear response evaluated in the random phase approximation. We discuss the density and temperature evolution of the pionic density which governs the quark condensate evolution. Numerical evaluations are performed.