Local perturbations perturb—exponentially–locally

Local perturbations perturb locally

Cosmological perturbations on local systems

We study the effect of cosmological expansion on orbits–galactic, planetary, or atomic–subject to an inverse-square force law. We obtain the laws of motion for gravitational or electrical interactions from general relativity–in particular, we find the gravitational field of a mass distribution in an expanding universe by applying perturbation theory to the Robertson-Walker metric. Cosmological ...

Gaussian sampling by local perturbations

We present a technique for exact simulation of Gaussian Markov random fields (GMRFs), which can be interpreted as locally injecting noise to each Gaussian factor independently, followed by computing the mean/mode of the perturbed GMRF. Coupled with standard iterative techniques for the solution of symmetric positive definite systems, this yields a very efficient sampling algorithm with essentia...

Local Critical Perturbations of Unimodal Maps

We introduce a new complete metric in the space V2 of unimodal Cmaps of the interval, with two maps close if they are close in the C-metric and differ only on a small interval containing their critical points. We identify all structurally stable maps in the sense of this metric. They are maps for which either (1) the trajectory of the critical point is attracted to a topologically attracting (a...

Loschmidt-echo decay from local boundary perturbations.

We investigate the sensitivity of the time evolution of semiclassical wave packets in two-dimensional chaotic billiards with respect to local perturbations of their boundaries. For this purpose, we address, analytically and numerically, the time decay of the Loschmidt echo (LE). We find the LE to decay exponentially in time, with the rate equal to the classical escape rate from an open billiard...