388 research outputs found
Quantum-corrected ultraextremal horizons and validity of WKB in massless limit
We consider quantum backreaction of the quantized scalar field with an
arbitrary mass and curvature coupling on ultraextremal horizons. The problem is
distinguished in that (in contrast to non-extremal or extremal black holes) the
WKB approximation remains valid near (which is the radius of the
horizon) even in the massless limit. We examine the behavior of the
stress-energy tensor of the quantized field near and show that
quantum-corrected objects under discussion do exist. In the limit of the large
mass our results agree with previous ones known in literature.Comment: revtex4, 9 page
Effects of high energy photon emissions in laser generated ultra-relativistic plasmas: real-time synchrotron simulations
We model the emission of high energy photons due to relativistic charged
particle motion in intense laser-plasma interactions. This is done within a
particle-in-cell code, for which high frequency radiation normally cannot be
resolved due to finite time steps and grid size. A simple expression for the
synchrotron radiation spectra is used together with a Monte-Carlo method for
the emittance. We extend previous work by allowing for arbitrary fields,
considering the particles to be in instantaneous circular motion due to an
effective magnetic field. Furthermore we implement noise reduction techniques
and present validity estimates of the method. Finally, we perform a rigorous
comparison to the mechanism of radiation reaction, and find the emitted energy
to be in excellent agreement with the losses calculated using radiation
reaction
Collective Phase Chaos in the Dynamics of Interacting Oscillator Ensembles
We study chaotic behavior of order parameters in two coupled ensembles of
self-sustained oscillators. Coupling within each of these ensembles is switched
on and off alternately, while the mutual interaction between these two
subsystems is arranged through quadratic nonlinear coupling. We show
numerically that in the course of alternating Kuramoto transitions to synchrony
and back to asynchrony, the exchange of excitations between two subpopulations
proceeds in such a way that their collective phases are governed by an
expanding circle map similar to the Bernoulli map. We perform the Lyapunov
analysis of the dynamics and discuss finite-size effects.Comment: 19 page
Scaling Properties of Weak Chaos in Nonlinear Disordered Lattices
The Discrete Nonlinear Schroedinger Equation with a random potential in one
dimension is studied as a dynamical system. It is characterized by the length,
the strength of the random potential and by the field density that determines
the effect of nonlinearity. The probability of the system to be regular is
established numerically and found to be a scaling function. This property is
used to calculate the asymptotic properties of the system in regimes beyond our
computational power.Comment: 4 pages, 5 figure
Hyperbolic Chaos of Turing Patterns
We consider time evolution of Turing patterns in an extended system governed
by an equation of the Swift-Hohenberg type, where due to an external periodic
parameter modulation long-wave and short-wave patterns with length scales
related as 1:3 emerge in succession. We show theoretically and demonstrate
numerically that the spatial phases of the patterns, being observed
stroboscopically, are governed by an expanding circle map, so that the
corresponding chaos of Turing patterns is hyperbolic, associated with a strange
attractor of the Smale-Williams solenoid type. This chaos is shown to be robust
with respect to variations of parameters and boundary conditions.Comment: 4 pages, 4 figure
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