Analysis of the Gravity Mode of a Pulsating Doradus-type Star

International audienceIn recent decades, asteroseismology has become a powerful tool in checking models for the structure and evolution of stars. From the perspective of asteroseismology, pulsating stars are invaluable. For this type of star, Doradus-type stars have a special feature. Since the atmosphere of such stars is in the transition phase from radiant state to convection state, gravity mode oscillations are visible in these stars. Since gravity modes are originated from central stellar regions, detecting them provides valuable information about these regions. In this study, photometric data of KIC11826272 provided by the Kepler satellite has been analyzed. The gravity mode's pattern and the average period have been determined. Deviation from the uniform ∆ in the form of a pattern is due to the mean rotation of the star. The rotational frequency splitting effect has increased the gravity mode's frequency. A decaying deviation found in the pattern represents prograde modes that are moving in the direction of rotation of the star. Finally, the degree of gravity mode has been determined

Multifractal clustering of passive tracers on a surface flow

We study the anomalous scaling of the mass density measure of Lagrangian tracers in a compressible flow realized on the free surface on top of a three dimensional flow. The full two dimensional probability distribution of local stretching rates is measured. The intermittency exponents which quantify the fluctuations of the mass measure of tracers at small scales are calculated from the large deviation form of stretching rate fluctuations. The results indicate the existence of a critical exponent $n_c \simeq 0.86$ above which exponents saturate, in agreement with what has been predicted by an analytically solvable model. Direct evaluation of the multi-fractal dimensions by reconstructing the coarse-grained particle density supports the results for low order moments.Comment: 7 pages, 4 figures, submitted to EP

Many-body effective mass enhancement in a two-dimensional electron liquid

Motivated by a large number of recent magnetotransport studies we have revisited the problem of the microscopic calculation of the quasiparticle effective mass in a paramagnetic two-dimensional (2D) electron liquid (EL). Our systematic study is based on a generalized $GW$ approximation which makes use of the many-body local fields and takes advantage of the results of the most recent QMC calculations of the static charge- and spin-response of the 2D EL. We report extensive calculations for the many-body effective mass enhancement over a broad range of electron densities. In this respect we critically examine the relative merits of the on-shell approximation, commonly used in weak-coupling situations, {\it versus} the actual self-consistent solution of the Dyson equation. We show that already for $r_s \simeq 3$ and higher, a solution of the Dyson equation proves here necessary in order to obtain a well behaved effective mass. Finally we also show that our theoretical results for a quasi-2D EL, free of any adjustable fitting parameters, are in good qualitative agreement with some recent measurements in a GaAs/AlGaAs heterostructure.Comment: 12 pages, 3 figures, CMT28 Conference Proceedings, work related to cond-mat/041226

General quantum algorithms for Hamiltonian simulation with applications to a non-Abelian lattice gauge theory

With a focus on universal quantum computing for quantum simulation, and through the example of lattice gauge theories, we introduce rather general quantum algorithms that can efficiently simulate certain classes of interactions consisting of correlated changes in multiple (bosonic and fermionic) quantum numbers with non-trivial functional coefficients. In particular, we analyze diagonalization of Hamiltonian terms using a singular-value decomposition technique, and discuss how the achieved diagonal unitaries in the digitized time-evolution operator can be implemented. The lattice gauge theory studied is the SU(2) gauge theory in 1+1 dimensions coupled to one flavor of staggered fermions, for which a complete quantum-resource analysis within different computational models is presented. The algorithms are shown to be applicable to higher-dimensional theories as well as to other Abelian and non-Abelian gauge theories. The example chosen further demonstrates the importance of adopting efficient theoretical formulations: it is shown that an explicitly gauge-invariant formulation using loop, string, and hadron (LSH) degrees of freedom simplifies the algorithms and lowers the cost compared with the standard formulations based on angular-momentum as well as the Schwinger-boson degrees of freedom. The LSH formulation further retains the non-Abelian gauge symmetry despite the inexactness of the digitized simulation, without the need for costly controlled operations. Such theoretical and algorithmic considerations are likely to be essential in quantum simulating other complex theories of relevance to nature.Comment: 59+17+7 pages, 16 figure

Trend of suicide in Iran during 2009 to 2012: Epidemiological evidences from national suicide registration

Background: Suicide behaviors cause a large portion of Disability adjusted life years worldwide. Objectives: The aim of this research was to study the trend, correlations and discrepancy of registered suicide incidents in Iran from 2009 to 2012 using data from the Iranian suicide registry. Materials and Methods: Suicide registry entries throughout the country between 2009 and 2012, including suicidal attempts and suicides, were collected. Data on age, gender, occupational, marital and residential status along with suicide method, history of previous attempt and history of medical or mental disorders were registered by health service provision staff at the service centers. Geographic mapping and statistical analysis were performed. Results: Amongst the 252911 attempted suicides during the period, we found suicide attempt and suicide rate of 30.5 - 44.8 and 1.76 - 2.23 per 100000 individuals, respectively, denoting overall suicide fatality rate of 2.63. The rate of suicide attempt in different provinces ranged between 0.7 and 271.1 and the rate of suicide between 0.17 and 17.7 per 100000 individuals. Attempted suicides showed more fatality in males, elderly, widow/widowers, divorced and unemployed subjects as well as in residents of rural areas. The most common attempt methods were medication overdose (84), and the mostcommonsuicide methods were hanging (30.3), medications overdose (28.1) and self-burning (17.9); these methods are found at different rates in various parts of the world. Conclusions: While the registry could provide us the most valid data on suicide, the wide range of suicide and suicide attempt rates in different provinces not only could question this statement but also could highlight the importance of studying the ethnic/geographic variations in suicide epidemiology with improved suicide registry and surveillance systems. � 2016, Mazandaran University of Medical Sciences

Pair Densities in a Two-dimensional Electron Gas (Jellium) at Strong Coupling from Scattering Theory with Kukkonen-Overhauser Effective Interactions

We present a calculation of the spin-averaged and spin-resolved pair distribution functions for a homogeneous gas of electrons moving in a plane with e2/r interactions at coupling strength rs = 10. The calculation is based on the solution of a two-electron scattering problem for both parallelspin- and antiparallel-spin-pairs interacting via effective spin-dependent many-body potentials. The scattering potentials are modeled within the approach proposed by Kukkonen and Overhauser to treat exchange and correlations under close constraints imposed by sum rules. We find very good agreement with quantum MonteCarlo data for the spin-averaged pair density. We also find that short-range pairing between parallel-spin electrons is beginning to emerge in the paramagnetic fluid at this coupling strength, as a precursor of a transition to a fully spin-polarized fluid state occurring at stronger coupling

Analytic theory of ground-state properties of a three-dimensional electron gas at varying spin polarization

We present an analytic theory of the spin-resolved pair distribution functions $g_{\sigma\sigma'}(r)$ and the ground-state energy of an electron gas with an arbitrary degree of spin polarization. We first use the Hohenberg-Kohn variational principle and the von Weizs\"{a}cker-Herring ideal kinetic energy functional to derive a zero-energy scattering Schr\"{o}dinger equation for $\sqrt{g_{\sigma\sigma'}(r)}$. The solution of this equation is implemented within a Fermi-hypernetted-chain approximation which embodies the Hartree-Fock limit and is shown to satisfy an important set of sum rules. We present numerical results for the ground-state energy at selected values of the spin polarization and for $g_{\sigma\sigma'}(r)$ in both a paramagnetic and a fully spin-polarized electron gas, in comparison with the available data from Quantum Monte Carlo studies over a wide range of electron density.Comment: 13 pages, 8 figures, submitted to Phys. Rev.

Regeneration of Stochastic Processes: An Inverse Method

We propose a novel inverse method that utilizes a set of data to construct a simple equation that governs the stochastic process for which the data have been measured, hence enabling us to reconstruct the stochastic process. As an example, we analyze the stochasticity in the beat-to-beat fluctuations in the heart rates of healthy subjects as well as those with congestive heart failure. The inverse method provides a novel technique for distinguishing the two classes of subjects in terms of a drift and a diffusion coefficients which behave completely differently for the two classes of subjects, hence potentially providing a novel diagnostic tool for distinguishing healthy subjects from those with congestive heart failure, even at the early stages of the disease development.Comment: 5 pages, two columns, 7 figs. to appear, The European Physical Journal B (2006

Bauschinger effect in thin metal films: Discrete dislocation dynamics study

The effects of dislocation climb on plastic deformation during loading and unloading are studied using a two-dimensional discrete dislocation dynamics model. Simulations are performed for polycrystalline thin films passivated on both surfaces. Dislocation climb lowers the overall level of the stress inside thin films and reduces the work hardening rate. Climb decreases the density of dislocations in pile-ups and reduces back stresses. These factors result in a smaller Bauschinger effect on unloading compared to simulations without climb. As dislocations continue to climb at the onset of unloading and the dislocation density continues to increase, the initial unloading slope increases with decreasing unloading rate. Because climb disperses dislocations, fewer dislocations are annihilated during unloading, leading to a higher dislocation density at the end of the unloading step.Engineering and Applied Science