Approximate scaling relation for the anharmonic electron-phonon problem

An approximate scaling relation is found for the transition temperature to a charge-density-wave instability in the anharmonic electron-phonon problem , which maps a wide range of interaction strengths, anharmonicities, and ph onon frequencies onto a common functional form. The relation employs the wa ve-function renormalization parameter and is valid even for systems that ar e not Fermi liquids.