Classical motion in force fields with short range correlations

We study the long time motion of fast particles moving through time-dependent random force fields with correlations that decay rapidly in space, but not necessarily in time. The time dependence of the averaged kinetic energy and mean-squared displacement is shown to exhibit a large degree of universality; it depends only on whether the force is, or is not, a gradient vector field. When it is, p^{2}(t) ~ t^{2/5} independently of the details of the potential and of the space dimension. Motion is then superballistic in one dimension, with q^{2}(t) ~ t^{12/5}, and ballistic in higher dimensions, with q^{2}(t) ~ t^{2}. These predictions are supported by numerical results in one and two dimensions. For force fields not obtained from a potential field, the power laws are different: p^{2}(t) ~ t^{2/3} and q^{2}(t) ~ t^{8/3} in all dimensions d\geq 1

Low-energy excitations in the three-dimensional random-field Ising model

The random-field Ising model (RFIM), one of the basic models for quenched disorder, can be studied numerically with the help of efficient ground-state algorithms. In this study, we extend these algorithm by various methods in order to analyze low-energy excitations for the three-dimensional RFIM with Gaussian distributed disorder that appear in the form of clusters of connected spins. We analyze several properties of these clusters. Our results support the validity of the droplet-model description for the RFIM.Comment: 10 pages, 9 figure

Website for psychological consultations

Elektroniskā sistēma ir izveidota cilvēkiem, kuriem ir kādas psiholoģiskās problēmas, kuri saprot problēmu esamību, bet nevar atrast palīdzību vai izrunāties pat tuviem cilvēkiem, tāpēc cieš vientulībā. Tā var būt ļoti noderīga cilvēkiem, kuriem finansiālās iespējas neļauj aprunāties ar psihologu, vai ļoti aizņemtiem cilvēkiem, kuriem nav tik daudz laika, lai doties pie profesionāla. Lietotāji var pastāstīt savu problēmu, uzdot jautājumus un uzzināt atbildes, izlasīt padomu gan no parastiem cilvēkiem, gan no profesionāliem. Katrs lietotājs drīkst komentēt cita lietotāja problēmu un, var būt, dalīties ar savu pieredzi līdzīgā situācijā. Moderatori un administratori uzturēs kārtību sistēmas vide. Administratori tajā pašā laikā kontrolēs galveno kopējo psiholoģisko tēmu izvirzīšanu.Electronic system is found for people who have some psychological problems, who understand the existence of problems, but cannot find support or talk to closest ones, so suffer alone. It may be very helpful to people whose financial facilities do not allow to talk to a psychologist or very busy people who do not have so much time to go to a professional. Users can share their problems, ask questions and find answers, read the advice from both ordinary people and the professionals. Each user is allowed to comment on other user's problem and may share his/her experience in a similar situation. Moderators and administrators maintain the order within the system. Administrators at the same time control common psychological main themes emphasizing

A Model for the Propagation of the Westward Traveling Surge

QC 2012041