We present exact analytical results for the statistics of nonlinear coupled oscillators under the influence of additive white noise. We suggest a perturbative approach for analysing the statistics of such systems under the action of a determanistic perturbation, based on the exact expressions for probability density functions for noise-driven oscillators. Using our perturbation technique we sho...

Bound state perturbation theory applies to the bound states of perturbed systems, for which the energy levels are discrete and separated from one another. The system may also have a continuous spectrum, but the interest is attached to the discrete states. The effects of perturbations on states of the continuous spectrum, or on discrete states imbedded in the continuum, require different techniq...

The experimental status of stable bound states made out of heavy quarks is reviewed. The need for a way to deal with the non-perturbative transitions involved calls for precision measurements on one hand, and for discovery of as yet undetected states to confirm predictions on the other. In this article, recent experimental contributions to heavy quarkonia spectroscopy and decay will be reviewed...

A constructive perturbation bound of the Drazin inverse of a square matrix is derived using a technique proposed by G. Stewart and based on perturbation theory for invariant subspaces. This is an improvement of the result published by the authors Wei and Li [Numer. Linear Algebra Appl., 10 (2003), pp. 563–575]. It is a totally new approach to developing perturbation bounds for the Drazin invers...

The changes in the nonnegative and positive polar factors of generalized polar decomposition and polar decomposition are studied under the additive perturbation. Some new perturbation bounds are obtained. These bounds are different from precious ones in form and measure and, in some cases, may be smaller than the corresponding existing ones. Furthermore, the corresponding perturbation bounds fo...

The purpose of this study was to investigate univariate relationships between perceived dysphonia and variation in pitch perturbation, amplitude perturbation, and additive noise. A time-domain, pitch-synchronous synthesis technique was used to generate sustained vowels varying in each of the three acoustic dimensions. A panel of trained listeners provided direct magnitude estimates of roughness...