  Transport properties of high transition temperature (high-Tc) superconductors
have been shown to have two distinct relaxation rates. We argue that this
apparent inconsistence can be resolved with an effective carrier density n
linear in temperature T. Experimental evidences both for and against this
explanation are analyzed and we conclude that this offers a simple yet
promising scenario. Above the pseudogap temperature T* the normal state of
high-Tc cuprates is close to a Fermi liquid. It however assumes non-Fermi-
liquid behaviors below T*.
