Quasi-classical physics and T-linear resistivity in both strongly correlated and ordinary metals

We show that near a quantum critical point generating quantum criticality of strongly correlated metals where the density of electron states diverges, the quasi-classical physics remains applicable to the description of the resistivity \rho of strongly correlated metals due to the presence of a transverse zero-sound collective mode, reminiscent of the phonon mode in solids. We demonstrate that at T, being in excess of an extremely low Debye temperature T_D, the resistivity \rho(T) changes linearly with T, since the mechanism, forming the T dependence of \rho(T), is the same as the electron-phonon mechanism that prevails at high temperatures in ordinary metals. Thus, electron-phonon scattering leads to near material-independence of the lifetime \tau of quasiparticles that is expressed as the ratio of the Planck constant \hbar to the Boltzmann constant k_B, T\tau\sim \hbar/k_B. We find that at T<T_D there exists a different mechanism, maintaining the T-linear dependence of \rho(T), and making the constancy of \tau fail in spite of the presence of T-linear dependence. Our results are in good agreement with exciting experimental observations.