Waiting time distribution for trains of quantized electron pulses

We consider a sequence of quantized Lorentzian pulses of non-interacting electrons impinging on a quantum point contact (QPC) and study the waiting time distribution (WTD), for any transmission and any number of pulses. As the degree of overlap between the electronic wave functions is tuned, the WTD reveals how the correlations between particles are modified. In the weak overlap regime, the WTD is made of several equidistant peaks, separated by the same period as the incoming pulses, contained in an almost exponentially decaying envelope. In the other limit, the WTD of a single quantum channel subjected to a constant voltage is recovered. In both cases, the WTD stresses the difference between the fluctuations induced by the scatterer and the ones encoded in the incoming quantum state. A clear cross-over between these two situations is studied with numerical and analytical calculations based on scattering theory.Comment: 12 pages, 4 figure

Noise in superconductor-quantum dot-normal metal structures in the Kondo regime

We consider a N-dot-S junction in the Kondo regime in the limit where the superconducting gap is much smaller than the Kondo temperature. A generalization of the floating of the Kondo resonance is proposed and many body corrections to the average subgap current are calculated. The zero frequency noise is computed and the Fano factor sticks to the value 10/3 for all voltages below the gap. Implications for finite frequency noise are briefly discussed

Waiting times of entangled electrons in normal-superconducting junctions

We consider a normal-superconducting junction in order to investigate the effect of new physical ingredients on waiting times. First, we study the interplay between Andreev and specular scattering at the interface on the distribution of waiting times of electrons or holes separately. In that case the distribution is not altered dramatically compared to the case of a single quantum channel with a quantum point contact since the interface acts as an Andreev mirror for holes. We then consider a fully entangled state originating from spliting of Cooper pairs at the interface and demonstrate a significant enhancement of the probability to detect two consecutive electrons in a short time interval. Finally, we discuss the electronic waiting time distribution in the more realistic situation of partial entanglement

Fingerprints of Majorana fermions in current-correlations measurements from a superconducting tunnel microscope

We compute various current correlation functions of electrons flowing from a topological nanowire to the tip of a superconducting scanning tunnel microscope and identify fingerprints of a Majorana bound state. In particular, the spin resolved cross-correlations are shown to display a clear distinction between the presence of a such an exotic state (negative correlations) and an Andreev bound state (positive correlations). Similarity and differences with measurements with a normal tunnel microscope are also discussed, like the robustness to finite temperature for instance.Comment: 7 pages, 2 figure

Photo-assisted shot noise in the fractional quantum Hall regime

The effect of an ac perturbation on the shot noise of a fractional quantum Hall fluid is studied at finite temperature. For a normal metal, it is known that the zero-frequency noise derivative exhibits steps as a function of bias voltage. In contrast, at Laughlin fractions, the backscattering noise exhibits evenly spaced singularities, which are reminiscent of tunneling density-of-states singularities for quasiparticles. The spacing is determined by the quasiparticle charge $\nu e$ and the ratio of the dc bias with respect to the drive frequency. Photo-assisted transport can thus be considered as a probe for effective charges of the quantum Hall effect.Comment: Proceeding of the 18th International Conference on Noise and Fluctuations, Salamanca, Spai

Photo-assisted shot noise in Coulomb interacting systems

We consider the fluctuations of the electrical current (shot noise) in the presence of a voltage time-modulation. For a non-interacting metal, it is known that the derivative of the photo-assisted noise has a staircase behavior. In the presence of Coulomb interactions, we show that the photo-assisted noise presents a more complex profile, in particular for the two following systems: 1) a two-dimensional electron gas in the fractional quantum Hall regime for which we have obtained evenly spaced singularities in the noise derivative, with a spacing related to the filling factor and, 2) a carbon nanotube for which a smoothed staircase in the noise derivative is obtained.Comment: Proceedings of the 6th Rencontres du Vietnam, Hanoi (2006

Notas sobre el proceso de conocimiento antropológico

Depto. de Antropología Social y Psicología SocialFac. de Ciencias Políticas y SociologíaTRUEpu

El grupo doméstico: concepto y realidades

Sin resume

Individuo, sociedad y antropología social

Depto. de Antropología Social y Psicología SocialFac. de Ciencias Políticas y SociologíaTRUEpu

La construcción de la salud y de la enfermedad

En el siguiente artículo se plantean los límites de la oposición entre lo biológico y lo social. Puede resultar clarificador, para un indispensable diálogo con la medicina, precisar las distintas dimensiones socioculturales que contribuyen a (e interfieren en) la construcción de la salud y de la enfermedad, en el campo social integrado por profesionales, profanos, médicos enfermos y profanos-enfermos. Al destacar los múltiples significados con los que se percibe lo orgánico, así como las relaciones con los sistemas médicos, el enfoque antropológico permite restituir la complejidad inherente al tema