We study non-autonomous planar Hamiltonian or reversible vector fields that vanish at the origin. The time-dependence is quasi-periodic with strongly non-resonant frequencies. First we give a simple criterion in terms of the averaged system for the trivial solution to be dynamically stable. Then we obtain destabilizations for classes of examples where the conditions of the criterion are not sat...

We study the linear stability problem of the stationary solution ψ∗ = − cos y for the Euler equation on a 2-dimensional flat torus of sides 2πL and 2π. We show that ψ∗ is stable if L ∈ (0, 1) and that exponentially unstable modes occur in a right neighborhood of L = n for any integer n. As a corollary, we gain exponentially instability for any L large enough and an unbounded growth of the numbe...

We consider how the time-dependent decay process of an unstable D-brane should be described in the full (quantum) open-closed string theory. It is argued that the system, starting from the unstable D-brane configuration, will evolve in time into the time-independent open string tachyon vacuum configuration which we assume to be finite, with the total energy conserved. As a concrete realization ...

This paper continues a study on Choptuik scaling in gravitational collapse of a massless complex scalar field at the threshold for black hole formation. We perform a linear perturbation analysis of the previously derived complex critical solution, and calculate the critical exponent for black hole mass, γ ≈ 0.387111 ± 0.000003. We also show that this critical solution is unstable via a growing ...

In this paper, the Floquet theory is combined with harmonic balance for the in-depth analysis of a Chua’s family circuit, exhibiting intermittence. Floquet multipliers are calculated along the periodic solution paths obtained through harmonic balance by means of a continuation algorithm. The analysis of both the stable and unstable solution sections enhances the information about the system and...

In the light of recent blackhole solutions inspired by string theory, we review some old statements on field theoretic hair on blackholes. We also discuss some stability issues. In particular we argue that the two dimensional string blackhole solution is semi-classically stable while the naked singularity is unstable to tachyon fluctuations. Finally we comment on the relation between the linear...

nifedipine (nif) a 1, 4-dihydropyridine calcium channel antagonist, undergoes photodegradation to nitroso analogues of dehydronifedipine (ndnif) when exposed to sunlight. photodegradation products of nif have no clinical activity, so different formulations of nif must remain unchanged. if nif preparations become unstable in exposure to light, they could cause therapeutic failure. the present st...

We formulate and prove a local stable manifold theorem for stochastic differential equations (SDEs) that are driven by spatial Kunita-type semimartingales with stationary ergodic increments. Both Stratonovich and Itôtype equations are treated. Starting with the existence of a stochastic flow for a SDE, we introduce the notion of a hyperbolic stationary trajectory. We prove the existence of inva...

In this paper, we use a methodology that was recently proposed by Antoniades and Christofides to compute the optimal actuator/sensor locations for the stabilization, via nonlinear static output feedback control, of the zero solution of the Kuramoto–Sivashinsky equation (KSE) for values of the instability parameter for which this solution is unstable. The theoretical results are illustrated thro...

We study the interior spike solutions to a steady state problem of the shadow system of the Gierer-Meinhardt system arising from biological pattern formation. We rst show that at a nondegenerate peak point the interior spike solution is locally unique and then we establish the spectrum estimates of the associated linearized operator. We also prove that the corresponding solution to the shadow s...