Simultaneous Softening of sigma and rho Mesons associated with Chiral   Restoration
  Complex poles of the unitarized pi-pi scattering amplitude in nuclear matter are studied. Partial restoration of chiral symmetry is modeled by the decrease of in-medium pion decay constant f*_{pi}.   For large chiral restoration (f*_{pi}/f_{pi} << 1),   2nd sheet poles in the scalar (sigma) and the vector (rho) mesons are both dictated by the Lambert W function and show universal softening as f*_{pi} decreases.   In-medium pi-pi cross section receives substantial contribution from the soft mode and exhibits a large enhancement in low-energy region.   Fate of this universality for small chiral restoration (f*_{pi}/f_{pi} ~ 1) is also discussed. 
K. Yokokawa (Univ. of Tokyo), T. Hatsuda (Univ. of Tokyo), A.   Hayashigaki (Univ. of Tokyo), T. Kunihiro (Kyoto Univ.)