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

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

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

Charge pumping and noise in a one-dimensional wire with weak electron-electron interactions

International audienceWe consider the adiabatic pumping of charge through a mesoscopic one dimensional wire in the presence of electron-electron interactions. A two-delta potential model is used to describe the wire, which allows to obtain exactly the scattering matrix coefficients, which are renormalized by the interactions. Two periodic drives, shifted one from another, are applied at two locations of the wire in order to drive a current through it in the absence of bias. Analytical expressions are obtained for the pumped charge, current noise, and Fano factor in different regimes. This allows to explore pumping for the whole parameter range of pumping strengths. We show that, working close to a resonance is necessary to have a comfortable window of pumping amplitudes where charge quantization is close to the optimum value: a single electron charge is transferred in one cycle. Interactions can improve the situation, the charge $Q$ is closer to one electron charge and noise is reduced, following a $Q \,(1-Q)$ behavior, reminiscent of the reduction of noise in quantum wires by $T \, (1-T)$, where $T$ is the energy transmission coefficient. For large pumping amplitudes, this charge vanishes, noise also decreases but slower than the charge

Full Counting Statistics of the momentum occupation numbers of the Tonks-Girardeau gas

We compute the fluctuations of the number of bosons with a given momentum for the Tonks-Girardeau gas at zero temperature. We show that correlations between opposite momenta, which is an important fingerprint of long range order in weakly interacting Bose systems, are suppressed and that the full distribution of the number of bosons with non zero momentum is exponential. The distribution of the quasi-condensate is however quasi Gaussian. Experimental relevance of our findings for recent cold atoms experiments are discussed.Comment: 10 pages, 4 figure

A Novel Bacterial 6-Phytase Improves Productive Performance, Precaecal Digestibility of Phosphorus, and Bone Mineralization in Laying Hens Fed a Corn-Soybean Meal Diet Low in Calcium and Available Phosphorus

Exogenous phytases are commonly added to low-phosphorus and low-calcium diets to improve P availability and reduce P excretion by poultry. This study investigated the effect of supplementation with a novel bacterial 6-phytase on egg production, egg quality, bone mineralization, and precaecal digestibility of P in laying hens fed corn-soybean meal-based diets. A total of 576 Hy-Line brown laying hens were used in a completely randomized block design at 25–45 weeks of age (woa). The three treatments included a positive control (PC) adequate-nutrient diet with 2840 kcal metabolizable energy/kg, 0.77% digestible lysine, 3.5% Ca, and 0.30% available P (avP); a negative control (NC) diet with 0.16% points less Ca and avP; and an NC diet supplemented with a novel bacterial 6-phytase at 300 phytase units/kg diet. Hen performance and the percentage of damaged eggs were measured every 4 weeks. Body weight, precaecal digestibility of P, and bone parameters at 45 woa were also measured. The reduction in avP and Ca in the NC diet did not compromise performance or egg quality. However, it decreased (P < 0.001) body weight, tibial dry matter, tibial ash and P content, and precaecal digestibility of P. Importantly, all these parameters were significantly improved (P < 0.001) and essentially restored to the levels measured in PC diet-fed hens upon supplementation with phytase. In summary, the present study demonstrates that the new bacterial 6-phytase could effectively counteract the negative effects of P and Ca deficiencies on body weight, bone mineralization, and P availability, thereby supporting high productivity without compromising the welfare of laying hens.info:eu-repo/semantics/publishedVersio

Microstructure and velocity of field-driven Ising interfaces moving under a soft stochastic dynamic

We present theoretical and dynamic Monte Carlo simulation results for the mobility and microscopic structure of 1+1-dimensional Ising interfaces moving far from equilibrium in an applied field under a single-spin-flip ``soft'' stochastic dynamic. The soft dynamic is characterized by the property that the effects of changes in field energy and interaction energy factorize in the transition rate, in contrast to the nonfactorizing nature of the traditional Glauber and Metropolis rates (``hard'' dynamics). This work extends our previous studies of the Ising model with a hard dynamic and the unrestricted SOS model with soft and hard dynamics. [P.A. Rikvold and M. Kolesik, J. Stat. Phys. 100, 377 (2000); J. Phys. A 35, L117 (2002); Phys. Rev. E 66, 066116 (2002).] The Ising model with soft dynamics is found to have closely similar properties to the SOS model with the same dynamic. In particular, the local interface width does not diverge with increasing field, as it does for hard dynamics. The skewness of the interface at nonzero field is very weak and has the opposite sign of that obtained with hard dynamics.Comment: 19 pages LaTex with 7 imbedded figure

A Novel Bacterial 6-Phytase Improves Growth Performance, Tibia Mineralization and Precaecal Digestibility of Phosphorus in Broilers: Data from Four Independent Performance Trials

A series of four broiler performance studies were conducted in different facilities to investigate the efficacy of a novel bacterial 6-phytase added at 500 FTU/kg diet on growth performance, bone mineralization and precaecal digestibility of phosphorus (pcdP) in broilers fed diets deficient in available P (avP) and calcium (Ca). The experimental design was the same for all studies, with each having three treatments: positive control (PC) diet formulated to meet or exceed the requirements of birds, negative control (NC) diet similarly reduced by 0.15% points in avP and Ca compared to the PC diet, and the NC diet supplemented with phytase (PHY) at 500 FTU/kg diet from 1 to 35 days of age. Body weight (BW) and feed intake were measured at 21 and 35 days of age, and average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (FCR), BW gain-corrected-FCR (cFCR), mortality and European performance efficiency factor (EPEF) were calculated. Tibia dry matter, tibia ash content and pcd of P were measured at 21 days of age in all experiments. The analysis of the data from the four experiments showed that compared with birds fed the adequate-nutrient diet, birds fed the NC diet resulted in a decrease (p < 0.05) in BW, ADG, ADFI and EPEF by 6.4, 6.3, 5.9 and 7.1%, respectively, and an increase in (p = 0.02) cFCR by 2.0%. The tibia dry matter and tibia ash content of these birds were also reduced (p < 0.001) by 3.8 and 4.0% points, respectively. PHY diets improved (p < 0.05) BW, ADG, ADFI, EPEF and cFCR by 8.0, 8.3, 7.3, 10.6 and 2.8%, respectively. Phytase addition at 500 FTU/kg diet also increased (p < 0.001) the tibia dry matter and tibia ash content by 3.5 and 4.2% points, respectively. The pcd of P was improved (p < 0.001) by 11.1 and 11.3% points, in comparison with NC and PC diets, respectively, when phytase was added. These performance parameters and tibia mineralization obtained with a diet supplemented with phytase were comparable to or better than the PC diet. The results demonstrated that avP and Ca could be lowered similarly by 0.15% points in broilers diets by using the new bacterial 6-phytase at 500 FTU/kg diet.info:eu-repo/semantics/publishedVersio