Iterated nonexpansive mappings

We present a further study on fixed point theory for the so called iterated nonexpansive mappings, that is, mappings which are nonexpansive along the orbits. They are a direct generalization of the contraction type maps studied by Rheinboldt in the late sixties of the last century. This is a wide class of nonlinear mappings including several families of generalized nonexpansive mappings appearing in the recent litherature.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Contribución al estudio de la flora balear

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Multichannel effects in Rashba quantum wires

We investigate intersubband mixing effects in multichannel quantum wires in the presence of Rashba spin-orbit coupling and attached to two terminals. When the contacts are ferromagnetic and their magnetization direction is perpendicular to the Rashba field, the spin-transistor current is expected to depend in a oscillatory way on the Rashba coupling strength due to spin coherent oscillations of the travelling electrons. Nevertheless, we find that the presence of many propagating modes strongly influences the spin precession effect, leading to (i) a quenching of the oscillations and (ii) strongly irregular curves for high values of the Rashba coupling. We also observe that in the case of leads' magnetization parallel to the Rashba field, the conductance departs from a uniform value as the Rashba strength increases. We also discuss the Rashba interaction induced current polarization effects when the contacts are not magnetic and investigate how this mechanism is affected by the presence of several propagating channels.Comment: 8 pages, 7 figure