Efficient implementation of a van der Waals density functional: Application to double-wall carbon nanotubes

We present an efficient implementation of the van der Waals density functional of Dion et al [Phys. Rev. Lett. 92, 246401 (2004)], which expresses the nonlocal correlation energy as a double spacial integral. We factorize the integration kernel and use fast Fourier transforms to evaluate the selfconsistent potential, total energy, and atomic forces, in N log(N) operations. The resulting overhead in total computational cost, over semilocal functionals, is very moderate for medium and large systems. We apply the method to calculate the binding energies and the barriers for relative translation and rotation in double-wall carbon nanotubes.Comment: 4 pages, 1 figure, 1 tabl

Dynamics of the Formation of Bright Solitary Waves of Bose-Einstein Condensates in Optical Lattices

We present a detailed description of the formation of bright solitary waves in optical lattices. To this end, we have considered a ring lattice geometry with large radius. In this case, the ring shape does not have a relevant effect in the local dynamics of the condensate, while offering a realistic set up to implement experiments with conditions usually not available with linear lattices (in particular, to study collisions). Our numerical results suggest that the condensate radiation is the relevant dissipative process in the relaxation towards a self-trapped solution. We show that the source of dissipation can be attributed to the presence of higher order dispersion terms in the effective mass approach. In addition, we demonstrate that the stability of the solitary solutions is linked with particular values of the width of the wavepacket in the reciprocal space. Our study suggests that these critical widths for stability depend on the geometry of the energy band, but are independent of the condensate parameters (momentum, atom number, etc.). Finally, the non-solitonic nature of the solitary waves is evidenced showing their instability under collisions.Comment: 7 pages, 7 figures, to appear in PR

Father’s parental leave use in Spain: the effect of education in the household

Producción CientíficaThe aim of this article is to present empirical evidence on the use of parental leave by fathers under the Mediterranean Welfare State, as a Spanish tribute to the legacy of Dr Rush in politics of fatherhood in a comparative perspective. We will focus on the Spanish case to analyze the use of paternity leave by fathers for the period 2001–2017. We consider the family unit – as a setting for bargaining and socialization – from a longitudinal perspective. The paper presents a very valuable and in-depth analysis of socio-demographic factors influencing the family decision to take parental leave by fathers (age, education, employment status, socio-economics). Based on the literature reviewed, we consider that these factors have a greater impact on how parental leave is used differently and how it has evolved over time. The case of Spain is interesting for the research because it represents a political and social model that combines a recent institutional commitment to the work/life balance through the extension of paternity leave for fathers with a male breadwinner family model still in transition

The correlation between unemployment and economic growth in Latin America – Okun’s law estimates by country

Producción CientíficaAbstract. The authors question the validity of Okunʼs law in Latin America in this paper. Based on several econometric models, they show that fluctuations in economic activity have a lesser impact on unemployment rates in Latin American countries than in other, more advanced economies. Instead of stimulus policies focused on reducing unemployment in general, these countries need targeted policies that encourage job creation in specific sectors. That being said, the unemployment– output ratio differs from one Latin American country to another. Where the ratio is weak or non-existent, cyclical variations adversely affect the quality of employment – another aspect that must also be addressed by economic policy.Ministerio deCiencia e Innovación,Grant/Award Number: PID2020-112509GB-I0

The Hamilton-Jacobi Formalism for Higher Order Field Theories

We extend the geometric Hamilton-Jacobi formalism for hamiltonian mechanics to higher order field theories with regular lagrangian density. We also investigate the dependence of the formalism on the lagrangian density in the class of those yelding the same Euler-Lagrange equations.Comment: 25 page