Publication
It is first shown that the thermal fluctuation effects on the transport and on the thermodynamic observables above the superconducting transition may provide, when they are analyzed simultaneously and consistently, a powerful tool to access the relaxation time, tau(0), of the Cooper pairs with wave vector k = 0 in high-temperature cuprate superconductors (HTSC). Then, Ne apply this procedure to optimally doped YBa2Cu3O7-delta (Y-123) crystals. It is found that in this HTSC tau(0) follows, within 20% accuracy, the BCS temperature behaviour and amplitude given by tau(0) = pi h/[8k(B)(T - T-c0)].