Statistical measure of complexity for quantum systems with continuous variables

The Fisher-Shannon statistical measure of complexity is analyzed for a continuous manifold of quantum observables. It is probed then than calculating it only in the configuration and momentum spaces will not give a complete description for certain systems. Then a more general measure for the complexity of a quantum system by the integration of the usual Fisher-Shannon measure over all the parameter space is proposed. Finally, these measures are applied to the concrete case of a free particle in a box.Comment: 6 pages, 5 figures. Published versio

A chiral Maxwell Demon

We investigate the role of chirality on the performance of a Maxwell demon implemented in a quantum Hall bar with a localized impurity. Within a stochastic thermodynamics description we investigate the ability of such a demon to drive a current against a bias. We show that the ability of the demon to perform is directly related to its ability to extract information from the system. The key features of the proposed Maxwell demon are the topological properties of the quantum Hall system. The asymmetry of the electronic interactions felt at the localized state when the magnetic field is reversed joined to the fact that we consider energy dependent (and asymmetric) tunneling barriers that connect such state with the Hall edge modes allow the demon to properly work.Comment: 5 pages, 5 figure

Scattering theory of nonlinear thermoelectric transport

We investigate nonlinear transport properties of quantum conductors in response to both electrical and thermal driving forces. Within scattering approach, we determine the nonequilibrium screening potential of a generic mesoscopic system and find that its response is dictated by particle and entropic injectivities which describe the charge and entropy transfer during transport. We illustrate our model analyzing the voltage and thermal rectification of a resonant tunneling barrier. Importantly, we discuss interaction induced contributions to the thermopower in the presence of large temperature differences.Comment: 5 pages, 3 figures; slightly shortened version to fulfill the journal's requirement

Dynamical Coulomb blockade of thermal transport

The role of energy exchange between a quantum system and its environment is investigated from the perspective of the Onsager conductance matrix. We consider the thermoelectric linear transport of an interacting quantum dot coupled to two terminals under the influence of an electrical potential and a thermal bias. We implement in our model the effect of coupling to electromagnetic environmental modes created by nearby electrons within the P(E)-theory of dynamical Coulomb blockade. Our findings relate the lack of some symmetries among the Onsager matrix coefficients with an enhancement of the efficiency at maximum power and the occurrence of the heat rectification phenomenon.Comment: 9 pages, 7 figure

The value of coskewness in mutual fund performance evaluation.

Recent asset pricing studies demonstrate the relevance of incorporating coskewness in asset pricing models, and illustrate how this component helps to explain the time variation of ex-ante market risk premiums. This paper analyzes the role of coskewness in mutual fund performance evaluation and finds evidence that adding a coskewness factor is economically and statistically significant. It documents that coskewness is sometimes managed and shows persistence of the coskewness policy over time. One of the most striking results is that many negative (positive) alpha funds, measured relative to the CAPM risk adjustments, would be reclassified as positive (negative) alpha funds using a model with coskewness. Therefore, performance ranking based on risk-adjusted returns without considering coskewness could generate an erroneous classification. Moreover, some fund characteristics, such as turnover ratio or category, are related to the likelihood of managing coskewness.Coskewness; Mutual funds; Performance measures;

The consumption/wealth and book/market ratios in a dynamic asset pricing contex.

This paper addresses new insights into the predictability of financial returns. In particular, we analyze two aspects of the controversial forecasting literature. On the one hand, we demonstrate a positive and contemporaneous link between aggregate book/market and consumption/wealth ratios. On the other hand, we show that real estate and human capital, as the present value of all future salaries, are key components of the consumption/wealth ratio in Spain. Specifically, we find that the cointegrating residuals of consumption, asset holdings, real estate holdings, and our measure of human capital provide a better forecast of future returns than does the standard proxy of the consumption/wealth ratio. This result is important because it clarifies the importance of country-specific components of wealth for cases in which the consumption/wealth ratio is employed as an instrument in conditional asset pricing models.Stock markets; Predictability; Consumption; Aggregate wealth; Book/market;

Can fundamentals explain cross-country correlations of asset returns?.

Previous studies show that existing correlations between national returns are higher than correlations between the national growth rates of fundamental variables. This paper examines the ability of intertemporal asset pricing models to explain cross-country correlations of national returns. We find that when capital markets are assumed to be fully integrated, a simple intertemporal general equilibrium model is able to explain the observed co-variability of domestic asset returns but generates too little variability in those returns. Results improve considerably if a less restrictive version is employed. In that setting, both domestic variability and cross-country co-variability of returns are consistent with capital market integration.Asset pricing models; Cross-country correlations;

Emergence of Majorana modes in cylindrical nanowires

We present calculations of Majorana edge modes in cylindrical nanowires of a semiconductor material with proximity-induced superconductivity. We consider a Rashba field along the transverse direction and an applied magnetic field in arbitrary orientation. Our analysis is based on exact numerical diagonalizations for the finite cylinder and on the complex band structure for the semi-infinite one. Orbital effects are responsible for a strong anisotropy of the critical field for which the effective gap vanishes. Robust Majorana modes are induced by the parallel field component and we find regimes with more than one Majorana mode on the same edge. Experimentally, they would manifest as a specific sequence of zero-bias conductances as a function of magnetic field. In the finite cylinder, a degradation of the Majorana modes due to interference of the two edges leads to oscillating non zero energies for large enough fields.Comment: 6 pages, 6 figure

Long-term KS_S-band photometric monitoring of L dwarfs

(abridged) We perform photometric time-series analysis of a sample of ten early to mid-L dwarfs in the field over three years of $K_s$-band observations with the OMEGA 2000 infrared camera of the 3.5m telescope on Calar Alto Observatory between January 2010 and December 2012. We perform $K_s$-band differential photometry of our targets (with typical errors of $\pm$15-30~mmag at the 1$\sigma$ level) by subtracting a reference flux from each photometric measurement. This reference flux is computed using three nearby, probably constant stars in the target's field-of-view. We then construct and visually inspect the light curves to search for variability, and use four different periodogram algorithms to look for possible periods in our photometric data. Our targets do not display long-term variability over 1$\sigma$ compared to other nearby stars of similar brightness, nor do the periodograms unveil any possible periodicity for these objects, with two exceptions: 2MASS~J02411151-0326587 and G196-3B. In the case of 2MASS~J02411151-0326587 (L0), our data suggest a tentative period of 307$\pm$21~days, at 40% confidence level, which seems to be associated with peak-to-peak variability of 44$\pm$10~mmag. This object may also display variability in timescales of years, as suggested by the comparison of our Ks-band photometry with 2MASS. For G196-3B (L3), we find peak-to-peak variations of 42$\pm$10~mmag, with a possible photometric period of 442$\pm$7~days, at 95% confidence level. This is roughly the double of the astrometric period reported by Zapatero Osorio (2014). Given the significance of these results, further photometric data are required to confirm the long-term variability.These results suggest that early- to mid-L dwarfs are fairly stable in the $K_s$-band within $\pm$90 mmag at the 3 $\sigma$ level over months to years, which covers hundreds to tens of thousands of rotation cycles.Comment: Accepted for publication in Astronomy & Astrophysic