Nearest neighbor embedding with different time delays

A nearest neighbor based selection of time delays for phase space reconstruction is proposed and compared to the standard use of time delayed mutual information. The possibility of using different time delays for consecutive dimensions is considered. A case study of numerically generated solutions of the Lorenz system is used for illustration. The effect of contamination with various levels of additive Gaussian white noise is discussed.Comment: 4 pages, 5 figures, updated to final versio

Theoretical study of interacting hole gas in p-doped bulk III-V semiconductors

We study the homogeneous interacting hole gas in $p$-doped bulk III-V semiconductors. The structure of the valence band is modelled by Luttinger's Hamiltonian in the spherical approximation, giving rise to heavy and light hole dispersion branches, and the Coulomb repulsion is taken into account via a self-consistent Hartree-Fock treatment. As a nontrivial feature of the model, the self-consistent solutions of the Hartree-Fock equations can be found in an almost purely analytical fashion, which is not the case for other types of effective spin-orbit coupling terms. In particular, the Coulomb interaction renormalizes the Fermi wave numbers for heavy and light holes. As a consequence, the ground state energy found in the self-consistent Hartree-Fock approach and the result from lowest-order perturbation theory do not agree. We discuss the consequences of our observations for ferromagnetic semiconductors, and for the possible observation of the spin-Hall effect in bulk $p$-doped semiconductors. Finally, we also investigate elementary properties of the dielectric function in such systems.Comment: 9 pages, 5 figures, title slightly changed in the course of editorial process, a few references added, version to appear in Phys. Rev.

Evidence of secondary relaxations in the dielectric spectra of ionic liquids

We investigated the dynamics of a series of room temperature ionic liquids based on the same 1-butyl-3-methyl imidazolium cation and different anions by means of broadband dielectric spectroscopy covering 15 decades in frequency (10^(-6)-10^9 Hz), and in the temperature range from 400 K down to 35 K. An ionic conductivity is observed above the glass transition temperature T_{g} with a relaxation in the electric modulus representation. Below T_{g}, two relaxation processes appear, with the same features as the secondary relaxations typically observed in molecular glasses. The activation energy of the secondary processes and their dependence on the anion are different. The slower process shows the characteristics of an intrinsic Johari-Goldstein relaxation, in particular an activation energy E_{beta}=24k_{B}T_{g} is found, as observed in molecular glasses.Comment: Major revision, submitted to Phys. Rev. Let

Equilibrium free energy measurement of a confined electron driven out of equilibrium

We study out-of equilibrium properties of a quantum dot in a GaAs/AlGaAs two-dimensional electron gas. By means of single electron counting experiments, we measure the distribution of work and dissipated heat of the driven quantum dot and relate these quantities to the equilibrium free energy change, as it has been proposed by C. Jarzynski [Phys. Rev. Lett. {\bf78}, 2690 (1997)]. We discuss the influence of the degeneracy of the quantized energy state on the free energy change as well as its relation to the tunnel rates between the dot and the reservoir.Comment: 5 pages, 4 figure

Commensurability effects in Andreev antidot billiards

An Andreev billiard was realized in an array of niobium filled antidots in a high-mobility InAs/AlGaSb heterostructure. Below the critical temperature T_C of the Nb dots we observe a strong reduction of the resistance around B=0 and a suppression of the commensurability peaks, which are usually found in antidot lattices. Both effects can be explained in a classical Kubo approach by considering the trajectories of charge carriers in the semiconductor, when Andreev reflection at the semiconductor-superconductor interface is included. For perfect Andreev reflection, we expect a complete suppression of the commensurability features, even though motion at finite B is chaotic.Comment: 4 pages, 4 figure

Twist glass transition in regioregulated poly(3-alkylthiophenes)s

The molecular structure and dynamics of regioregulated poly(3-butylthiophene) (P3BT), poly(3-hexylthiophene)(P3HT), and poly(3-dodecylthiophene) (P3DDT) were investigated using Fourier transform infrared absorption (FTIR), solid state $^{13}$C nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) measurements. In the DSC measurements, the endothermic peak was obtained around 340 K in P3BT, and assigned to enthalpy relaxation that originated from the glass transition of the thiophene ring twist in crystalline phase from results of FTIR, $^{13}$C cross-polarization and magic-angle spinning (CPMAS) NMR, $^{13}$C spin-lattice relaxation time measurements, and centerband-only detection of exchange (CODEX) measurements. We defined this transition as {\it twist-glass transition}, which is analogous to the plastic crystal - glassy crystal transition.Comment: 9 pages, 10 figures, 2 tables. Phys.Rev.B, in pres

Spatial patterns of desynchronization bursts in networks

We adapt a previous model and analysis method (the {\it master stability function}), extensively used for studying the stability of the synchronous state of networks of identical chaotic oscillators, to the case of oscillators that are similar but not exactly identical. We find that bubbling induced desynchronization bursts occur for some parameter values. These bursts have spatial patterns, which can be predicted from the network connectivity matrix and the unstable periodic orbits embedded in the attractor. We test the analysis of bursts by comparison with numerical experiments. In the case that no bursting occurs, we discuss the deviations from the exactly synchronous state caused by the mismatch between oscillators

Age-period-cohort analysis of Swiss suicide data, 1881-2000

At the end of the 19th century, male suicide rates in Switzerland were as high as the respective rates in recent decades, whereas female suicide rates were distinctly lower. An age-period-cohort analysis was performed to provide more information about the genderspecific changes over the last century. Suicide mortality has been reported in Switzerland since 1876 when the standardised registration of mortality data began. The analysed data cover the period 1881-2000. The statistical analyses were based on log-linear models and data aggregated by 10-year age-intervals and 10-year periodintervals. The results indicate similar age and period effects in males and females. The estimates representing age-specific risk increase steadily with age, with intermediate plateaus in the 20s and the 50s. The period-specific estimates follow the economic cycles. The birth cohort effects are stronger in males and weaker in females. In the males' estimates, there is a peak in cohorts born around 1840 and a low in cohorts born some 60-100 years later. The estimates increased again in generations born after World War II. In females, the birth cohort estimates are low in cohorts born in the first half of the 19th century and increase until the first half of the 20th century. Birth cohort effects remain an intriguing topic in epidemiology of suicide. A better understanding of birth cohort effects might open new doors to suicide preventio

Magnetic ground state and spin fluctuations in MnGe chiral magnet as studied by Muon Spin Rotation

We have studied by muon spin resonance ({\mu}SR) the helical ground state and fluctuating chiral phase recently observed in the MnGe chiral magnet. At low temperature, the muon polarization shows double period oscillations at short time scales. Their analysis, akin to that recently developed for MnSi [A. Amato et al., Phys. Rev. B 89, 184425 (2014)], provides an estimation of the field distribution induced by the Mn helical order at the muon site. The refined muon position agrees nicely with ab initio calculations. With increasing temperature, an inhomogeneous fluctuating chiral phase sets in, characterized by two well separated frequency ranges which coexist in the sample. Rapid and slow fluctuations, respectively associated with short range and long range ordered helices, coexist in a large temperature range below T$_{N}$ = 170 K. We discuss the results with respect to MnSi, taking the short helical period, metastable quenched state and peculiar band structure of MnGe into account.Comment: 13 pages, 11 figure