In this paper, we investigate theoretically the possible development of instabilities in fiber-reinforced elastomers (and other soft materials) when they are subjected to finitestrain loading conditions. We focus on the physically relevant class of ‘‘macroscopic’’ instabilities, i.e., instabilities with wavelengths that are much larger than the characteristic size of the underlying microstructu...

A series of resonances has been observed in the absorption of a 100% amplitude-modulated laser beam by an optically pumped sodium atomic beam. Resonances were observed when the modulation frequency was equal to the first, second, and third subharmonic of the Rabi frequency. The experimental results are compared with theory, and the implications of these parametric resonances to laser instabilit...

– We consider a population of parametrically excited globally coupled oscillators in a weakly nonlinear state. The instabilities of collective modes lead to a traveling-wave regime, where intensities of oscillations of each oscillator vary periodically in time. For large excitation amplitudes a frozen state with nearly uniform oscillation intensities is observed. Ensembles of coupled oscillator...

We investigate the possibility that electromagnetic fluctuations are amplified in expanding universe by parametric resonance, during the oscillatory regime of a scalar field to which they are coupled. We consider scalar electrodynamics and we find that electromagnetic fluctuations undergo exponential instabilities. This mechanism could have some relevance for the problem of large scale primordi...

This work studies the practicality of using finite-time Lyapunov exponents (FTLEs) to detect the inception of parametric resonance for vessels operating in irregular longitudinal seas. Parametrically excited roll motion is modelled as a single degree-of-freedom system, with nonlinear damping and restoring terms. FTLEs are numerically calculated at every integration time step. Using this numeric...