Adan Garriga

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We calculate analytically the fluctuation-dissipation ratio (FDR) for Ising ferromagnets quenched to criticality, both for the long-range model and its short-range analog in the limit of large dimension. Our exact solution shows that, for both models, if the system is unmagnetized while if the initial magnetization is nonzero. This indicates that two(More)
Due to high computational costs, the physics governed by the wave equation in 3-D is often modelled via discrete-time numerical simulations conducted in 2-D scenarios. Results are normally generalized to 3-D rather straightforwardly, overlooking the fact that the propagation of a point-like impulse in 2-D exhibits the so-called afterglow phenomenon, which(More)
We introduce an exactly solvable model for glassy dynamics with many relaxational modes, each one characterized by a different relaxational time scale. Analytical solution of the aging dynamics at low temperatures shows that a nonequilibrium or effective temperature can be associated to each time scale or mode. The spectrum of effective temperatures shows(More)
The space and time discretization inherent to all FDTD schemes introduce non-physical dispersion errors, i.e. deviations of the speed of sound from the theoretical value predicted by the governing Euler differential equations. A general methodology for computing this dispersion error via straightforward numerical simulations of the FDTD schemes is(More)
We analyze fluctuation-dissipation relations in the backgammon model: a system that displays glassy behavior at zero temperature due to the existence of entropy barriers. We study local and global fluctuation relations for the different observables in the model. For the case of a global perturbation we find a unique negative fluctuation-dissipation ratio(More)
This thesis is about algorithms and complex phenomena in networks. In the first part we study a network model of stochastic spiking neurons. We propose a modeling technique based on a mesoscopic description level and show the presence of a phase transition around a critical coupling strength. We derive a local plasticity which drives the network towards the(More)
We calculate analytically the fluctuation-dissipation ratio (FDR) for Ising ferromagnets quenched to criticality, both for the long-range model and its short-range analogue in the limit of large dimension. Our exact solution shows that, for both models, X∞ = 1/2 if the system is unmagnetized while X∞ = 4/5 if the initial magnetization is non-zero. This(More)
We investigate the validity of a zeroth thermodynamic law for nonequilibrium systems. In order to describe the thermodynamics of the glassy systems, it has been introduced an extra parameter, the effective temperature which generalizes the fluctuation-dissipation theorem (FDT) to off-equilibrium systems and supposedly describes thermal fluctuations around(More)
This report aims to give an overall idea of 3D audio technologies in a physics point of view. Some of the most representative methods are revised and discussed. Ambisonics technique is specially analised due to its powerful and complete approach. In order to ”see” for ourselves its strengths and drawbacks we implemented and tested a basic Ambisonics(More)