2,582 research outputs found
Numerical Simulations of Random Phase Sine-Gordon Model and Renormalization Group Predictions
Numerical Simulations of the random phase sine-Gordon model suffer from
strong finite size effects preventing the non-Gaussian component of
the spatial correlator from following the universal infinite volume prediction.
We show that a finite size prediction based on perturbative Renormalisation
Group (RG) arguments agrees well with new high precision simulations for small
coupling and close to the critical temperature.Comment: 13 pages, 3 ps figures. Extensive new numerical simulation
Bond diluted Levy spin-glass model and a new finite size scaling method to determine a phase transition
A spin-glass transition occurs both in and out of the limit of validity of
mean-field theory on a diluted one dimensional chain of Ising spins where
exchange bonds occur with a probability decaying as the inverse power of the
distance. Varying the power in this long-range model corresponds, in a
one-to-one relationship, to change the dimension in spin-glass short-range
models. Using different finite size scaling methods evidence for a spin-glass
transition is found also for systems whose equivalent dimension is below the
upper critical dimension at zero magnetic field. The application of a new
method is discussed, that can be exported to systems in a magnetic field.Comment: 8 pages, 8 figures, 1 tabl
A proposal of a Renormalization Group transformation
We propose a family of renormalization group transformations characterized by
free parameters that may be tuned in order to reduce the truncation effects. As
a check we test them in the three dimensional XY model. The Schwinger--Dyson
equations are used to study the renormalization group flow.Comment: Contribution to Lattice'94. uuencoded postscript fil
On the validity of the Boltzmann equation to describe low density granular systems
The departure of a granular gas in the instable region of parameters from the
initial homogeneous cooling state is studied. Results from Molecular Dynamics
and from Direct Monte Carlo simulation of the Boltzmann equation are compared.
It is shown that the Boltzmann equation accurately predicts the low density
limit of the system. The relevant role played by the parallelization of the
velocities as time proceeds and the dependence of this effect on the density is
analyzed in detail
Transversal inhomogeneities in dilute vibrofluidized granular fluids
The spontaneous symmetry breaking taking place in the direction perpendicular
to the energy flux in a dilute vibrofluidized granular system is investigated,
using both a hydrodynamic description and simulation methods. The latter
include molecular dynamics and direct Monte Carlo simulation of the Boltzmann
equation. A marginal stability analysis of the hydrodynamic equations, carried
out in the WKB approximation, is shown to be in good agreement with the
simulation results. The shape of the hydrodynamic profiles beyond the
bifurcation is discussed
Velocity distribution of fluidized granular gases in presence of gravity
The velocity distribution of a fluidized dilute granular gas in the direction
perpendicular to the gravitational field is investigated by means of Molecular
Dynamics simulations. The results indicate that the velocity distribution can
be exactly described neither by a Gaussian nor by a stretched exponential law.
Moreover, it does not exhibit any kind of scaling. In fact, the actual shape of
the distribution depends on the number of monolayers at rest, on the
restitution coefficient and on the height at what it is measured. The role
played by the number of particle-particle collisions as compared with the
number of particle-wall collisions is discussed
Nonlinear model predictive control of a passenger vehicle for automated lane changes
This article presents a nonlinear Model Predictive Control (MPC) for lane changes, based on a simplified Single Track Model (STM) of the vehicle. The STM includes the position of the vehicle in global coordinates as a state so that the position of the target lane can be specified to the MPC for reference tracking. Moreover, a constraint for maintaining a safety distance with the vehicles in the target lane is included. Simulation results show the effectiveness of the MPC in scenarios with different initial conditions that demonstrate the correct implementation of the safety distance constraint
Finite-size scaling study of the d=4 site-diluted Ising
We study the four dimensional site-diluted Ising model using finite-size
scaling techniques. We explore the whole parameter space (density-coupling) in
order to determine the Universality Class of the transition line. Our data are
compatible with Mean Field behavior plus logarithmic corrections.Comment: Contribution to LATTICE 9
On some exceptional cases in the integrability of the three-body problem
We consider the Newtonian planar three--body problem with positive masses
, , . We prove that it does not have an additional first
integral meromorphic in the complex neighborhood of the parabolic Lagrangian
orbit besides three exceptional cases ,
, where the linearized equations are shown to be partially
integrable. This result completes the non-integrability analysis of the
three-body problem started in our previous papers and based of the
Morales-Ramis-Ziglin approach.Comment: 7 page
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