12,350 research outputs found
Convergence to Equilibrium in Wasserstein distance for damped Euler equations with interaction forces
We develop tools to construct Lyapunov functionals on the space of
probability measures in order to investigate the convergence to global
equilibrium of a damped Euler system under the influence of external and
interaction potential forces with respect to the 2-Wasserstein distance. We
also discuss the overdamped limit to a nonlocal equation used in the modelling
of granular media with respect to the 2-Wasserstein distance, and provide
rigorous proofs for particular examples in one spatial dimension
Structure preserving schemes for the continuum Kuramoto model: phase transitions
The construction of numerical schemes for the Kuramoto model is challenging
due to the structural properties of the system which are essential in order to
capture the correct physical behavior, like the description of stationary
states and phase transitions. Additional difficulties are represented by the
high dimensionality of the problem in presence of multiple frequencies. In this
paper, we develop numerical methods which are capable to preserve these
structural properties of the Kuramoto equation in the presence of diffusion and
to solve efficiently the multiple frequencies case. The novel schemes are then
used to numerically investigate the phase transitions in the case of identical
and non identical oscillators
Non-Gaussianity and gravitational wave background in curvaton with a double well potential
We study the density perturbation by a curvaton with a double well potential
and estimate the nonlinear parameters for non-Gaussianity and the amplitude of
gravitational wave background generated during inflation. The predicted
nonlinear parameters strongly depend on the size of a curvaton self-coupling
constant as well as the reheating temperature after inflation for a given
initial amplitude of the curvaton. The difference from usual massive
self-interacting curvaton is also emphasized.Comment: 23 pages, 6 figure
Modulated reheating by curvaton
There might be a light scalar field during inflation which is not responsible
for the accelerating inflationary expansion. Then, its quantum fluctuation is
stretched during inflation. This scalar field could be a curvaton, if it decays
at a late time. In addition, if the inflaton decay rate depends on the light
scalar field expectation value by interactions between them, density
perturbations could be generated by the quantum fluctuation of the light field
when the inflaton decays. This is modulated reheating mechanism. We study
curvature perturbation in models where a light scalar field does not only play
a role of curvaton but also induce modulated reheating at the inflaton decay.
We calculate the non-linearity parameters as well as the scalar spectral index
and the tensor-to-scalar ratio. We find that there is a parameter region where
non-linearity parameters are also significantly enhanced by the cancellation
between the modulated effect and the curvaton contribution. For the simple
quadratic potential model of both inflaton and curvaton, both tensor-to-scalar
ratio and nonlinearity parameters could be simultaneously large.Comment: 26 pages, 22 figure
An analytical framework for a consensus-based global optimization method
In this paper we provide an analytical framework for investigating the
efficiency of a consensus-based model for tackling global optimization
problems. This work justifies the optimization algorithm in the mean-field
sense showing the convergence to the global minimizer for a large class of
functions. Theoretical results on consensus estimates are then illustrated by
numerical simulations where variants of the method including nonlinear
diffusion are introduced
Mean-field limit for collective behavior models with sharp sensitivity regions
We rigorously show the mean-field limit for a large class of swarming
individual based models with local sharp sensitivity regions. For instance,
these models include nonlocal repulsive-attractive forces locally averaged over
sharp vision cones and Cucker-Smale interactions with discontinuous
communication weights. We construct global-in-time defined notion of solutions
through a differential inclusion system corresponding to the particle
descriptions. We estimate the error between the solutions to the differential
inclusion system and weak solutions to the expected limiting kinetic equation
by employing tools from optimal transport theory. Quantitative bounds on the
expansion of the 1-Wasserstein distance along flows based on a weak-strong
stability estimate are obtained. We also provide different examples of
realistic sensitivity sets satisfying the assumptions of our main results
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