Effect of noise for two interacting particles in a random potential

We investigated the effect of noise on propagation of two interacting particles pairs in a quasi one--dimensional random potential. It is shown that pair diffusion is strongly enhanced by short range interaction comparing with the non--interacting case.Comment: 8 Latex pages + 3 postscript figures uu- compressed submitted to Europhysics Letter

Societal level gender inequalities amplify gender gaps in problem solving more than in academic disciplines

Although digital transformations can help narrow existing gender gaps in labour market outcomes, this change depends, among several factors, on the extent to which females have the skills to make the most of new opportunities. An important such skill is problem solving. We examined gender gaps in cognitive and attitudinal dimensions of problem solving and how between-country differences in such gaps are related to societal level gender inequality. This study involved 237,115 students from 42 countries surveyed in the 2012 round of the Programme for Internation Student Assessment (PISA). Analyses revealed that, on average across the countries considered, males outperformed females on cognitive dimensions of problem solving (d = 0.127) and held more positive attitudes towards problem solving (d = 0.193). However, gender gaps varied across countries. In countries with greater gender inequality, the gender gap in the problem solving performance of 15-year-olds in favour of males was more pronounced than in countries with lower levels of gender inequality (r = 0.27). The association between country-level gender inequality and the gender gap in mathematics, reading, and science was r = 0.20 for mathematics, r = 0.22 for reading, and r = 0.02 for science. Males' advantage in problem-solving performance was in addition to any relationship between gender inequality and the gender gap in text comprehension, mathematics, and the country's level of economic development. By contrast, the gender gap in problem solving attitudes in favour of males was smaller in countries with greater gender inequality (r = −0.42)

Why don't more boys want to become teachers? The effect of a gendered profession on students’ career expectations

Gender differences in teaching career expectations were explored among 15-year-old students in 49 countries participating in the 2015 cycle of the Programme for International Student Assessment (PISA). Results revealed that boys were generally less likely than girls to expect to work as teachers, but the magnitude of the gender gap varied across countries. Boys were more likely to expect to work as teachers in countries with a greater representation of male teachers and in countries with higher teacher salaries. In countries with more egalitarian gender beliefs (i.e., beliefs and attitudes toward gender equality), both boys and girls were less likely to expect teaching careers, but this negative association was stronger for boys than for girls

Renormalization and Quantum Scaling of Frenkel-Kontorova Models

We generalise the classical Transition by Breaking of Analyticity for the class of Frenkel-Kontorova models studied by Aubry and others to non-zero Planck's constant and temperature. This analysis is based on the study of a renormalization operator for the case of irrational mean spacing using Feynman's functional integral approach. We show how existing classical results extend to the quantum regime. In particular we extend MacKay's renormalization approach for the classical statistical mechanics to deduce scaling of low frequency effects and quantum effects. Our approach extends the phenomenon of hierarchical melting studied by Vallet, Schilling and Aubry to the quantum regime.Comment: 14 pages, 1 figure, submitted to J.Stat.Phy

What School Factors are Associated with the Success of Socio-Economically Disadvantaged Students? An Empirical Investigation Using PISA Data

Many school-level policies, such as school funding formulae and teacher allocation mechanisms, aim at reducing the influence of students’ low socio-economic condition on academic achievement. Benchmarks and indicators based on large-scale international assessments can be used to measure academic success and identify if and when disadvantaged students are successful. We build on such work and develop a new method for identifying a cross-country comparable metric of the academic success of socio-economically disadvantaged students using data from the Programme for International Student Assessment (PISA). We estimate the prevalence of successful disadvantaged students in 56 countries, as well as changes over time between 2006 and 2015. In addition, we focus on the PISA 2015 edition and explore school factors associated with the probability that disadvantaged students will be successful academically in a subsample of 18 countries. Findings reveal that successful disadvantaged students attend schools with a better disciplinary climate and that provide additional time for instruction in key subjects

What School Factors are Associated with the Success of Socio-Economically Disadvantaged Students? An Empirical Investigation Using PISA Data

Many school-level policies, such as school funding formulae and teacher allocation mechanisms, aim at reducing the influence of students’ low socio-economic condition on academic achievement. Benchmarks and indicators based on large-scale international assessments can be used to measure academic success and identify if and when disadvantaged students are successful. We build on such work and develop a new method for identifying a cross-country comparable metric of the academic success of socio-economically disadvantaged students using data from the Programme for International Student Assessment (PISA). We estimate the prevalence of successful disadvantaged students in 56 countries, as well as changes over time between 2006 and 2015. In addition, we focus on the PISA 2015 edition and explore school factors associated with the probability that disadvantaged students will be successful academically in a subsample of 18 countries. Findings reveal that successful disadvantaged students attend schools with a better disciplinary climate and that provide additional time for instruction in key subjects

Ground state wavefunction of the quantum Frenkel-Kontorova model

The wavefunction of an incommensurate ground state for a one-dimensional discrete sine-Gordon model -- the Frenkel-Kontorova (FK) model -- at zero temperature is calculated by the quantum Monte Carlo method. It is found that the ground state wavefunction crosses over from an extended state to a localized state when the coupling constant exceeds a certain critical value. So, although the quantum fluctuation has smeared out the breaking of analyticity transition as observed in the classical case, the remnant of this transition is still discernible in the quantum regime.Comment: 5 Europhys pages, 3 EPS figures, accepted for publication in Europhys. Letter

Quantum Fractal Fluctuations

We numerically analyse quantum survival probability fluctuations in an open, classically chaotic system. In a quasi-classical regime, and in the presence of classical mixed phase space, such fluctuations are believed to exhibit a fractal pattern, on the grounds of semiclassical arguments. In contrast, we work in a classical regime of complete chaoticity, and in a deep quantum regime of strong localization. We provide evidence that fluctuations are still fractal, due to the slow, purely quantum algebraic decay in time produced by dynamical localization. Such findings considerably enlarge the scope of the existing theory.Comment: revtex, 4 pages, 5 figure

A simple variational approach to the quantum Frenkel-Kontorova model

We present a simple and complete variational approach to the one-dimensional quantum Frenkel-Kontorova model. Dirac's time-dependent variational principle is adopted together with a Hatree-type many-body trial wavefunction for the atoms. The single-particle state is assumed to have the Jackiw-Kerman form. We obtain an effective classical Hamiltonian for the system which is simple enough for a complete numerical solution for the static ground state of the model. Numerical results show that our simple approach captures the essence of the quantum effects first observed in quantum Monte Carlo studies.Comment: 12 pages, 2 figure

Quantum Signatures of The Classical Disconnection Border

A quantum Heisenberg model with anisotropic coupling and all-to-all interaction has been analyzed using the Bose-Einstein statistics. In Ref.\cite{jsp} the existence of a classical energy disconnection border (EDB) in the same kind of models has been demonstrated. We address here the problem to find quantum signatures of the EDB. An independent definition of a quantum disconnection border, motivated by considerations strictly valid in the quantum regime is given. We also discuss the dynamical relevance of the quantum border with respect to quantum magnetic reversal. Contrary to the classical case the magnetization can flip even below the EDB through Macroscopic Quantum Tunneling. We evaluate the time scale for magnetic reversal from statistical and spectral properties, for a small number of particles and in the semiclassical limit.Comment: 5 pages, 5 figure