2,926 research outputs found
Resonantly enhanced and diminished strong-field gravitational-wave fluxes
The inspiral of a stellar mass () compact body into a
massive () black hole has been a focus of much effort,
both for the promise of such systems as astrophysical sources of gravitational
waves, and because they are a clean limit of the general relativistic two-body
problem. Our understanding of this problem has advanced significantly in recent
years, with much progress in modeling the "self force" arising from the small
body's interaction with its own spacetime deformation. Recent work has shown
that this self interaction is especially interesting when the frequencies
associated with the orbit's and motions are in an integer ratio:
, with and
both integers. In this paper, we show that key aspects of the self
interaction for such "resonant" orbits can be understood with a relatively
simple Teukolsky-equation-based calculation of gravitational-wave fluxes. We
show that fluxes from resonant orbits depend on the relative phase of radial
and angular motions. The purpose of this paper is to illustrate in simple terms
how this phase dependence arises using tools that are good for strong-field
orbits, and to present a first study of how strongly the fluxes vary as a
function of this phase and other orbital parameters. Future work will use the
full dissipative self force to examine resonant and near resonant strong-field
effects in greater depth, which will be needed to characterize how a binary
evolves through orbital resonances.Comment: 25 pages, 6 figures, 4 tables. Accepted to Phys Rev D; accepted
version posted here, including referee feedback and other useful comment
Maxwell-Drude-Bloch dissipative few-cycle optical solitons
We study the propagation of few-cycle pulses in two-component medium
consisting of nonlinear amplifying and absorbing two-level centers embedded
into a linear and conductive host material. First we present a linear theory of
propagation of short pulses in a purely conductive material, and demonstrate
the diffusive behavior for the evolution of the low-frequency components of the
magnetic field in the case of relatively strong conductivity. Then, numerical
simulations carried out in the frame of the full nonlinear theory involving the
Maxwell-Drude-Bloch model reveal the stable creation and propagation of
few-cycle dissipative solitons under excitation by incident femtosecond optical
pulses of relatively high energies. The broadband losses that are introduced by
the medium conductivity represent the main stabilization mechanism for the
dissipative few-cycle solitons.Comment: 38 pages, 10 figures. submitted to Physical Review
Cascades and Dissipative Anomalies in Nearly Collisionless Plasma Turbulence
We develop first-principles theory of kinetic plasma turbulence governed by
the Vlasov-Maxwell-Landau equations in the limit of vanishing collision rates.
Following an exact renormalization-group approach pioneered by Onsager, we
demonstrate the existence of a "collisionless range" of scales (lengths and
velocities) in 1-particle phase space where the ideal Vlasov-Maxwell equations
are satisfied in a "coarse-grained sense". Entropy conservation may
nevertheless be violated in that range by a "dissipative anomaly" due to
nonlinear entropy cascade. We derive "4/5th-law" type expressions for the
entropy flux, which allow us to characterize the singularities
(structure-function scaling exponents) required for its non-vanishing.
Conservation laws of mass, momentum and energy are not afflicted with anomalous
transfers in the collisionless limit. In a subsequent limit of small gyroradii,
however, anomalous contributions to inertial-range energy balance may appear
due both to cascade of bulk energy and to turbulent redistribution of internal
energy in phase space. In that same limit the "generalized Ohm's law" derived
from the particle momentum balances reduces to an "ideal Ohm's law", but only
in a coarse-grained sense that does not imply magnetic flux-freezing and that
permits magnetic reconnection at all inertial-range scales. We compare our
results with prior theory based on the gyrokinetic (high gyro-frequency) limit,
with numerical simulations, and with spacecraft measurements of the solar wind
and terrestrial magnetosphere.Comment: Several additions have been made that were requested by the referees
of the PRX submission. In particular, discussion previously relegated to
Supplemental Materials are now included in the main text as appendice
Quasi-Two-Dimensional Dynamics of Plasmas and Fluids
In the lowest order of approximation quasi-twa-dimensional dynamics of planetary atmospheres and of plasmas in a magnetic field can be described by a common convective vortex equation, the Charney and Hasegawa-Mirna (CHM) equation. In contrast to the two-dimensional Navier-Stokes equation, the CHM equation admits "shielded vortex solutions" in a homogeneous limit and linear waves ("Rossby waves" in the planetary atmosphere and "drift waves" in plasmas) in the presence of inhomogeneity. Because of these properties, the nonlinear dynamics described by the CHM equation provide rich solutions which involve turbulent, coherent and wave behaviors. Bringing in non ideal effects such as resistivity makes the plasma equation significantly different from the atmospheric equation with such new effects as instability of the drift wave driven by the resistivity and density gradient. The model equation deviates from the CHM equation and becomes coupled with Maxwell equations. This article reviews the linear and nonlinear dynamics of the quasi-two-dimensional aspect of plasmas and planetary atmosphere starting from the introduction of the ideal model equation (CHM equation) and extending into the most recent progress in plasma turbulence.U. S. Department of Energy DE-FG05-80ET-53088Ministry of Education, Science and Culture of JapanFusion Research Cente
Soliton Interactions in Perturbed Nonlinear Schroedinger Equations
We use multiscale perturbation theory in conjunction with the inverse
scattering transform to study the interaction of a number of solitons of the
cubic nonlinear Schroedinger equation under the influence of a small correction
to the nonlinear potential. We assume that the solitons are all moving with the
same velocity at the initial instant; this maximizes the effect each soliton
has on the others as a consequence of the perturbation. Over the long time
scales that we consider, the amplitudes of the solitons remain fixed, while
their center of mass coordinates obey Newton's equations with a force law for
which we present an integral formula. For the interaction of two solitons with
a quintic perturbation term we present more details since symmetries -- one
related to the form of the perturbation and one related to the small number of
particles involved -- allow the problem to be reduced to a one-dimensional one
with a single parameter, an effective mass. The main results include
calculations of the binding energy and oscillation frequency of nearby solitons
in the stable case when the perturbation is an attractive correction to the
potential and of the asymptotic "ejection" velocity in the unstable case.
Numerical experiments illustrate the accuracy of the perturbative calculations
and indicate their range of validity.Comment: 28 pages, 7 figures, Submitted to Phys Rev E Revised: 21 pages, 6
figures, To appear in Phys Rev E (many displayed equations moved inline to
shorten manuscript
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