Hall resistivity of granular metals

We calculate the Hall conductivity \sig_{xy} and resistivity $\rho_{xy}$ of a granular system at large tunneling conductance $g_{T}\gg 1$. We show that in the absence of Coulomb interaction the Hall resistivity depends neither on the tunneling conductance nor on the intragrain disorder and is given by the classical formula $\rho_{xy}=H/(n^* e c)$, where $n^*$ differs from the carrier density $n$ inside the grains by a numerical coefficient determined by the shape of the grains. The Coulomb interaction gives rise to logarithmic in temperature $T$ correction to $\rho_{xy}$ in the range \Ga \lesssim T \lesssim \min(g_T E_c,\ETh), where \Ga is the tunneling escape rate, $E_c$ is the charging energy and \ETh is the Thouless energy of the grain.Comment: 4 pages, 1 figur

Effect of connecting wires on the decoherence due to electron-electron interaction in a metallic ring

We consider the weak localization in a ring connected to reservoirs through leads of finite length and submitted to a magnetic field. The effect of decoherence due to electron-electron interaction on the harmonics of AAS oscillations is studied, and more specifically the effect of the leads. Two results are obtained for short and long leads regimes. The scale at which the crossover occurs is discussed. The long leads regime is shown to be more realistic experimentally.Comment: LaTeX, 4 pages, 4 eps figure

Generalizing the DGLAP Evolution of Fragmentation Functions to the Smallest x Values

An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches.Comment: 10 pages, 3 figure

Dark states in the magnetotransport through triple quantum dots

We consider the transport through a system of three coupled quantum dots in a perpendicular magnetic field. At zero field, destructive interference can trap an electron in a dark state -- a coherent superposition of dot states that completely blocks current flow. The magnetic field can disrupt this interference giving rise to oscillations in the current and its higher-order statistics as the field is increased. These oscillations have a period of either the flux-quantum or half the flux-quantum, depending on the dot geometry. We give results for the stationary current and for the shotnoise and skewness at zero and finite frequency.Comment: 7 pages, 7 figure