CRITICAL-BEHAVIOR OF LIQUID-HE-4 AT NEGATIVE PRESSURES

We examine the equation of state of liquid He-4 at negative pressures close to the spinodal density rho(s) where the hydrodynamic speed of s ound vanishes. The non-analytic behavior of the equation of state and the speed of sound in the vicinity of the spinodal density are calcula ted in two and in three dimensions; we find for the speed of sound the non-analytic behavior mc(s)(2) similar to (rho - rho(s))(2/5) in thre e dimensions and mc(s)(2) similar to [(rho - rho(s))/\ln(rho - rho(s)) \](1/2) in two dimensions. We then examine the low density regime nume rically, using a semi-analytic microscopic theory. It is found that no n-analytic exponents are visible only in a negligible density regime a round the spinodal point. Estimates for the spinodal densities, and th e range of critical fluctuations are provided.