In this thesis we study the influence of a time-dependent perturbation on transport properties of mesoscopic systems, such as open quantum dots or metal wires. Recent weak localization measurements showed a discrepancy with theoretical calculations that considered the electron-electron interaction semiclassically. We demonstrate that a quantum mechanical treatment gives a small correction to the semiclassical theory in the weak localization regime. We conclude that other mechanisms, such as external microwave radiation, should be taken into account to explain observed experimental results.; The second part of the thesis treats the effect of external radiation on a novel object of mesoscopic physics—ballistic quantum dots. We develop a time-dependent random matrix theory to calculate the electric current through open quantum dots subjected to an external oscillating field. We discuss effects of the field on statistical properties of conductance and photovoltaic current (electron pumping). We calculate both the weak localization correction to the conductance and the conductance fluctuations for an arbitrary strength of the oscillating field. We show that at low frequency, conductance fluctuations are suppressed by the external field, while the weak localization correction is not sensitive to low-frequency perturbations. We demonstrate that the external field broadens the electron distribution function in the dot, thus producing heating. The heating effect does not change the conductance fluctuations, which depend on temperature of electrons in the leads, but it changes the photovoltaic current through the dot. We also study the photovoltaic current noise through open quantum dots subjected to external perturbations.
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