A stability criterion for energetic particle‐Alfvén modes

PFC / JA - 90 - 27 A Stability Criterion for Energetic Particle - Alfv 6 n Modes

A simple criterion for structurally fixed modes

A property of linear systems is called structural if it can be deduced solely from the presence of zeroes at certain entries of the matrices of the system. aIn physical terms, the presence of zeroes in the matrices of the system indicates the absence of specified interconnections, and is therefore indicative of the structure of the system. Structural controllability has been studied for both si...

Local stability criterion for self-gravitating disks in modified gravity

We study local stability of self-gravitating fluid and stellar disk in the context of modified gravity theories which predict a Yukawa-like term in the gravitational potential of a point mass. We investigate the effect of such a Yukawa-like term on the dynamics of self-gravitating disks. More specifically, we investigate the consequences of the presence of this term for the local stability of t...

A Stability Criterion for Systems with Neutrally Stable Modes and Deadzone Nonlinearities

Stability analysis is considered for feedback interconnections of dead-zone nonlinearities with linear systems that has a neutrally stable mode. Such systems do not have a unique equilibrium point and the standard techniques from passivity and Lyapunov theory cannot be applied. A stability criterion that generalizes the Popov criterion for this class of systems is derived in this report and sev...

Criterion for stability of Goldstone modes and Fermi liquid behavior in a metal with broken symmetry.

There are few general physical principles that protect the low-energy excitations of a quantum phase. Of these, Goldstone's theorem and Landau-Fermi liquid theory are the most relevant to solids. We investigate the stability of the resulting gapless excitations--Nambu-Goldstone bosons (NGBs) and Landau quasiparticles--when coupled to one another, which is of direct relevance to metals with a br...