CUBERO GÓMEZ , David

Se ha analizado diversos aspectos de la teoría cinética y la hidrodinámica de los flujos granulares diluidos, utilizando como punto de partida un modelo sencillo de esferas duras inelásticas. ... ;,'serif'; font-size: 12pt"> Se ha estudiado el estado más sencillo que puede presentar un medio granular que evoluciona libremente, el denominado...

The authors concluded that the coarse-graining dynamics of a one-dimensional chain of oscillators interacting through Lennard–Jones potentials is Markovian, in contrast with the situation observed for harmonic lattices. However, with the help of a novel equation that relates the correlation of forces and momenta, I show that this conclusion is...

The dynamics of a system formed by a finite number N of globally coupled bistable oscillators and driven by external forces is studied focusing on a global variable defined as the arithmetic mean of each oscillator variable. Several models based on truncation schemes of a hierarchy of stochastic equations for a set of fluctuating cumulant...

We use a fast Fourier transform block Lanczos diagonalization algorithm to study the electronic states of excess electrons in fluid alkanes (methane, ethane, and propane) and in a molecular model of amorphous polyethylene (PE) relevant to studies of space charge in insulating polymers. We obtain a new pseudopotential for electron–PE...

We use a pseudopotential model to calculate the electronic states available to an excess electron in crystalline and amorphous regions of model polyethlyene as well as the molecular crystal of the linear alkane C27H56. It is shown that alkane crystals of whatever chain length are not representative of crystalline polyethylene (PE) although they...

We use a simple mean field scheme to compute the polarization energy of an excess electron in amorphous polyethylene that allows us to study dynamical properties. Nonadiabatic simulations of an excess electron in amorphous polyethylene at room temperature show the spontaneous formation of localized small polaron states in which the electron is...

Recent molecular-dynamics simulations show that a dilute relativistic gas equilibrates to a Jüttner velocity distribution if ensemble velocities are measured simultaneously in the observer frame. The analysis of relativistic Brownian motion processes, on the other hand, implies that stationary one-particle distributions can differ depending on...

The operation of Brownian motors is usually described in terms of out-of-equilibrium and symmetrybreaking settings, with the relevant spatiotemporal symmetries identified from the analysis of the equations of motion for the system at hand. When the appropriate conditions are satisfied,symmetry related trajectories with opposite current are...

The theoretical treatment of quasi periodically driven quantum systems is complicated by the inapplicability of the Floquet theorem, which requires strict periodicity. In this work we consider a quantum system driven by a biharmonic driving and examine its asymptotic long-time limit, the limit in which features distinguishing systems with...

We consider the problem of the control of transport in higher-dimensional periodic structures by applied ac fields. In a generic crystal, transverse degrees of freedom are coupled, and this makes the control of motion difficult to implement. We show, both with simulations and with an analytical functional expansion on the driving amplitudes,...

This work extends the domain of vibrational mechanics to higher dimensions, with fast vibrations applied to different directions. In particular, the presented analysis considers the case of a split biharmonic drive, where harmonics of frequency ω and 2 ω are applied to orthogonal directions in a two-dimensional setting. It is shown, both...

We use projection operators to address the coarse-grained multiscale problem in harmonic systems. Stochastic equations of motion for the coarse-grained variables with an inhomogeneous level of coarse graining in both time and space are presented. In contrast to previous approaches that typically start with thermodynamic averages the key element...

We show that the Markovian approximation assumed in current particle-based coarse-grained techniques, like dissipative particle dynamics, is unreliable in situations in which sound plays an important role. As an example we solve analytically and numerically the dynamics of coarse-grained harmonic systems by using first principle methods,...

We study the surface states of an excess electron at polyethylene/vacuum interfaces using an accurate reaction-field method, specifically designed to take into account the long range interaction of the excess electron and the dielectric surface. The method is shown to validate the energy levels recently reported with a simple perturbation...

This work explores the possibility to arbitrarily shape in space low-frequency magnetic fields using a recently introduced synthesization technique (Choi et al., 2016). We investigate the ability to focus a magnetic field on a two-dimensional region using magnetic field sources distributed on a parallel plane. In agreement with the recent work,...

Directed transport in ratchets is determined by symmetry breaking in a system out of equilibrium. A hallmark of rocking ratchets is current reversals: an increase in the rocking force changes the direction of the current. In this work for a biharmonically driven spatially symmetric rocking ratchet we show that a class of current reversal is...

The steady state of a low-density gas of inelastic hard spheres confined between two parallel walls at the same temperature is studied. Because of the dissipation in collisions, the state is not uniform but highly inhomogeneous with a nonlinear temperature profile. Direct Monte Carlo simulations show that in the nearly elastic limit the...

We analyze the relationship between irrationality and quasiperiodicity in nonlinear driven systems. To that purpose, we consider a nonlinear system whose steady-state response is very sensitive to the periodic or quasiperiodic character of the input signal. In the infinite time limit, an input signal consisting of two incommensurate frequencies...

We examine the time-dependent behavior of a nonlinear system driven by a two-frequency forcing. By using a nonperturbative approach, we are able to derive an asymptotic expression, valid in the long-time limit, for the time average of the output variable which describes the response of the system. We identify several universal features of the...

We report computer simulations of an excess electron in various structural motifs of polyethylene at room temperature, including lamellar and interfacial regions between amorphous and lamellae, as well as nanometre-sized voids. Electronic properties such as density of states, mobility edges, and mobilities are computed on the different phases...

Polyethylene is commonly used as an insulator for AC power cables. However it is known to undergo chemical and physical change which can lead to dielectric breakdown. Despite almost eighty years of experimental characterization of its electrical properties, very little is known about the details of the electrical behaviour of this material at...

By applying a staggered driving force in a prototypical discrete model with a quartic nonlinearity, we demonstrate the spontaneous formation and destruction of discrete breathers with a selected frequency due to thermal fluctuations. The phenomenon exhibits the striking features of stochastic resonance (SR): a nonmonotonic behavior as noise is...

The response of a linear system to an external perturbation is governed by the Fourier limit, with the inverse of the interaction time constituting a lower limit for the system bandwidth. This does not hold for nonlinear systems, which can thus exhibit sub-Fourier-behavior. The present Letter identifies a mechanism for sub-Fourier-sensitivity...