  Path integral Monte Carlo (PIMC) simulations of liquid helium at negative
pressure have been carried out for a temperature range from the critical
temperature to below the superfluid transition. We have calculated the
temperature dependence of the spinodal line as well as the pressure dependence
of the isothermal sound velocity in the region of the spinodal. We discuss the
slope of the superfluid transition line and the shape of the dispersion curve
at negative pressures.
