Stochastic pumps are models of artificial molecular machines which are driven by periodic time variation of parameters, such as site and barrier energies. The no-pumping theorem states that no directed motion is generated by variation of only site or
barrier energies [S. Rahav, J. Horowitz, and C. Jarzynski, Phys. Rev. Lett., 101, 140602 (2008)]. We study stochastic pumps of several interacting particles and demonstrate that the net current of particles satisfy an additional no- pumping theorem.
Absolute resistivity measurements as a function of temperature from optimally doped YBa_2Cu_3O_(7), La_(2-x)Sr_xCuO_4, Bi_2Sr_2CaCu_2O_(8-x), and (Ca_0.1La_0.9)(Ba_1.65La_0.35)Cu_3O_y thin films are reported. Special attention is given to the measure
ment geometrical factors and the resistivity slope between Tc and T^{*}. The results are compared with a strong coupling theory for the resistivity derivative near T_c, which is based on hard core bosons (HCB), and with several weak coupling theories, which are BCS based. Surprisingly, our results agree with both paradigms. The implications of these findings and the missing calculations needed to distinguish between the two paradigms are discussed.
