Search results for "Names"

Subharmonic excitation of the eigenmodes of charged particles in a Penning trap

2004

When parametrically excited, a harmonic system reveals a nonlinear dynamical behaviour which is common to non-deterministic phenomena. The ion motion in a Penning trap -- which can be regarded as a system of harmonic oscillators -- offers the possibility to study anharmonic characteristics when perturbed by an external periodical driving force. In our experiment we excited an electron cloud stored in a Penning trap by applying an additional quadrupole r.f. field to the endcaps. We observed phenomena such as individual and center-of-mass oscillations of an electron cloud and fractional frequencies, so-called subharmonics, to the axial oscillation. The latter show a characteristic threshold b…

Mixing of Two-Quasiparticle Configurations

2007

In this chapter we discuss configuration mixing of two-quasiparticle states. It is caused by the residual interaction remaining beyond the quasiparticle mean field defined in Chap. 13. We derive the equations of motion by the EOM method developed in Sect. 11.1. To accomplish this we need to express the residual Hamiltonian in terms of quasiparticles.

Generalized Nutbrown representation of the vector vertex function and the magnetic moment of the chargedρmeson

1975

A former representation of the vector vertex function, due to Nutbrown, is generalized. It is shown how this resolves an apparent contradiction between the effective-Lagrangian and hard-meson techniques. Further possible applications are discussed. (AIP)

Beyond the Runge–Gross Theorem

2012

The Runge–Gross theorem (Runge and Gross, Phys Rev Lett, 52:997–1000, 1984) states that for a given initial state the time-dependent density is a unique functional of the external potential. Let us elaborate a bit further on this point. Suppose we could solve the time-dependent Schrodinger equation for a given many-body system, i.e. we specify an initial state \(| \Uppsi_0 \rangle\) at \(t=t_0\) and evolve the wavefunction in time using the Hamiltonian \({\hat{H}} (t).\) Then, from the wave function, we can calculate the time-dependent density \(n (\user2{r},t).\) We can then ask the question whether exactly the same density \(n(\user2{r},t)\) can be reproduced by an external potential \(v^…

Time-Independent Canonical Perturbation Theory

2001

First we consider the perturbation calculation only to first order, limiting ourselves to only one degree of freedom. Furthermore, the system is to be conservative, ∂ H∕∂ t = 0, and periodic in both the unperturbed and perturbed case. In addition to periodicity, we shall require the Hamilton–Jacobi equation to be separable for the unperturbed situation. The unperturbed problem H0(J0) which is described by the action-angle variables J0 and w0 will be assumed to be solved. Thus we have, for the unperturbed frequency: $$\displaystyle{ \nu _{0} = \frac{\partial H_{0}} {\partial J_{0}} }$$ (10.1) and $$\displaystyle{ w_{0} =\nu _{0}t +\beta _{0}\;. }$$ (10.2) Then the new Hamiltonian reads, up t…

Anomalous thermalization of nonlinear opticalwave systems

2011

In complete analogy with a system of classical particules colliding inside a gas medium, an incoherent optical field can evolve, owing to nonlinearity, towards a thermodynamic equilibrium state [1]. In this respect, the spatiotemporal dynamics of the light field is governed by the nonlinear Schrodinger equation and its equilibrium spectrum has been determined in the framework of the weak turbulence theory [1,2]. It is expected that experiments made in the field of nonlinear optics can possibly lead to the observation of turbulence or thermalization of nonlinear waves [1,2]. Here we present experimental, theoretical and numerical studies of different optical systems presenting an unusual the…

Arresting soliton collapse in two-dimensional nonlinear Schrödinger systems via spatiotemporal modulation of the external potential

2007

We predict stable, collapse-free solitonslike structures in two-dimensional nonlinear Schr\"odinger systems in subdiffractive regimes, accomplished by a spatiotemporal modulation of the external potential. We investigate the scaling laws, the stability, and the dynamical properties of these subdiffractive solitons.

Corrigendum to “Transition from ideal to viscous Mach cones in a kinetic transport approach” [Phys. Lett. B 710 (4–5) (2012) 641]

2014

Suppression of soliton self-frequency shift by up-shifted filtering

2002

We propose an efficient method for suppressing the soliton self-frequency shift in high-speed transmission lines by means of up-shifted filters.

INSTABILITIES IN DOPPLER BROADENED OPTICALLY PUMPED FAR-INFRARED LASERS

1988

Recently Weiss and Brock observed Lorenz-type chaos in the 81.5μm emission from an optically-pumped 14NH3 laser1. The theoretical interpretation of the experimental results is an open question, however. In fact, the Lorenz-Haken model refers to incoherently pumped lasers with homogeneously-broadened two-level active media2. Models based on (at least) a three-level system are needed to describe optically-pumped lasers, whose dynamics is known to reduce to that of the Lorez-Haken model under certain limiting conditions3. But these conditions are not met in the 14NH3 laser, and indeed theoretical predictions of a model for this laser, which considered a homogeneously-broadened three-level acti…