Search results for "Planck"

Little Randall-Sundrum models:ϵKstrikes again

2009

A detailed phenomenological analysis of neutral kaon mixing in ``little Randall-Sundrum'' models is presented. It is shown that the constraints arising from the $CP$-violating quantity ${ϵ}_{K}$ can, depending on the value of the ultraviolet cutoff, be even stronger than in the original Randall-Sundrum scenario addressing the hierarchy problem up to the Planck scale. The origin of the enhancement is explained, and a bound ${\ensuremath{\Lambda}}_{\mathrm{UV}}g\mathrm{\text{several}}$ ${10}^{3}\text{ }\text{ }\mathrm{TeV}$ is derived, below which vast corrections to ${ϵ}_{K}$ are generically unavoidable. Implications for nonstandard ${Z}^{0}\ensuremath{\rightarrow}b\overline{b}$ couplings ar…

New insights into black bodies

2012

Planck's law describes the radiation of black bodies. The study of its properties is of special interest, as black bodies are a good description for the behavior of many phenomena. In this work a new mathematical study of Planck's law is performed and new properties of this old acquaintance are obtained. As a result, the exact form for the locus in a color-color diagrams has been deduced, and an analytical formula to determine with precision the black body temperature of an object from any pair of measurements has been developed. Thus, using two images of the same field obtained with different filters, one can compute a fast estimation of black body temperatures for every pixel in the image…

The role of the Planck scale in black hole radiance

2008

Lorentz invariance plays a pivotal role in the derivation of the Hawking effect, which crucially requires an integration in arbitrarily small distances or, equivalently, in unbounded energies. New physics at the Planck scale could, therefore, potentially modify the emission spectrum. We argue, however, that the kinematic invariance can be deformed in such a way that the thermal spectrum remains insensitive to trans-Planckian physics.

Nonlinear response of superparamagnets with finite damping: an analytical approach

2004

The strongly damping-dependent nonlinear dynamical response of classical superparamagnets is investigated by means of an analytical approach. Using rigorous balance equations for the spin occupation numbers a simple approximate expression is derived for the nonlinear susceptibility. The results are in good agreement with those obtained from the exact (continued-fraction) solution of the Fokker-Planck equation. The formula obtained could be of assistance in the modelling of the experimental data and the determination of the damping coefficient in superparamagnets.

How to solve Fokker-Planck equation treating mixed eigenvalue spectrum?

2013

An analogy of the Fokker-Planck equation (FPE) with the Schr\"odinger equation allows us to use quantum mechanics technique to find the analytical solution of the FPE in a number of cases. However, previous studies have been limited to the Schr\"odinger potential with a discrete eigenvalue spectrum. Here, we will show how this approach can be also applied to a mixed eigenvalue spectrum with bounded and free states. We solve the FPE with boundaries located at x=\pm L/2 and take the limit L\rightarrow\infty, considering the examples with constant Schr\"{o}dinger potential and with P\"{o}schl-Teller potential. An oversimplified approach was proposed earlier by M.T. Araujo and E. Drigo Filho. A…

Probabilistic description of traffic breakdowns

2001

We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply to the probabilistic model regarding the jam emergence as the formation of a large car cluster on highway. In these terms the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster model. We assume that, first, the growth of the car cluster is governed by attachment of cars to the cluster whose rate is mainly determined by the mean headway distance between the car in the vehicle flow and, may be, also by the headway distance in the cluster. Second, the cluster dissolution is determined by the car …

Cosmological limits on neutrino unknowns versus low redshift priors

2015

Recent Cosmic Microwave Background (CMB) temperature and polarization anisotropy measurements from the Planck mission have significantly improved previous constraints on the neutrino masses as well as the bounds on extended models with massless or massive sterile neutrino states. However, due to parameter degeneracies, additional low redshift priors are mandatory in order to sharpen the CMB neutrino bounds. We explore here the role of different priors on low redshift quantities, such as the Hubble constant, the cluster mass bias, and the reionization optical depth $\tau$. Concerning current priors on the Hubble constant and the cluster mass bias, the bounds on the neutrino parameters may di…

A Langevin Approach to the Diffusion Equation

2002

We propose a generalized Langevin equation as a model for the diffusion equation of air pollution in the atmosphere. We write down a partial stochastic differential equation for the pollutant concentration, which we solve exactly obtaining the first and the second moment of the pollutant concentration. We obtain a linear multiplicative stochastic differential equation for the Fourier components of the concentration, which can be used to calculate higher moments of the concentration. We obtain the exact steady state solution in the case of neutral atmosphere and a general expression of the mean concentration as a function of the fluctuation intensity of the wind speed, the diffusion coeffici…

The Fokker-Planck Equation

2009

Stochastic Dynamics of Ferroelectric Polarization

2008

This study is addressed to the conceptual and technical problems emerging for ferroelectric systems out of thermodynamic equilibrium. The theoretical setup includes a lattice of interacting cells, each cell obeying regular dynamics determined by Ginzburg-Landau model Hamiltonians whereas relaxation toward minimum energy state is reproduced by thermal environment. Representative examples include polarization response of a single lattice cell, birth of a domain as triggered by the ergodicity breaking, and the effect of nonlocal electroelastic interaction all evidenced combining the Fokker-Planck, imaginary time Schrodinger and symplectic integration techniques.