2,746 research outputs found
Formation of the resonant system HD 60532
Among multi-planet planetary systems there are a large fraction of resonant
systems. Studying the dynamics and formation of these systems can provide
valuable informations on processes taking place in protoplanetary disks where
the planets are thought have been formed. The recently discovered resonant
system HD 60532 is the only confirmed case, in which the central star hosts a
pair of giant planets in 3:1 mean motion resonance. We intend to provide a
physical scenario for the formation of HD 60532, which is consistent with the
orbital solutions derived from the radial velocity measurements. Observations
indicate that the system is in an antisymmetric configuration, while previous
theoretical investigations indicate an asymmetric equilibrium state. The paper
aims at answering this discrepancy as well. We performed two-dimensional
hydrodynamical simulations of thin disks with an embedded pair of massive
planets. Additionally, migration and resonant capture are studied by
gravitational N-body simulations that apply properly parametrized
non-conservative forces. Our simulations suggest that the capture into the 3:1
mean motion resonance takes place only for higher planetary masses, thus
favouring orbital solutions having relatively smaller inclination i=20 degrees.
The system formed by numerical simulations qualitatively show the same
behaviour as HD 60532. We also find that the presence of an inner disk (between
the inner planet and the star) plays a very important role in determining the
final configurations of resonant planetary systems. Its damping effect on the
inner planet's eccentricity is responsible for the observed antisymmetric state
of HD 60532.Comment: 7 pages, 7 figures, Accepted for publication in Astronomy &
Astrophysic
Cooperative Dynamics of an Artificial Stochastic Resonant System
We have investigated cooperative dynamics of an artificial stochastic
resonant system, which is a recurrent ring connection of neuron-like signal
transducers (NST) based on stochastic resonance (SR), using electronic circuit
experiments. The ring showed quasi-periodic, tunable oscillation driven by only
noise. An oscillation coherently amplified by noise demonstrated that SR may
lead to unusual oscillation features. Furthermore, we found that the ring
showed synchronized oscillation in a chain network composed of multiple rings.
Our results suggest that basic functions (oscillation and synchronization) that
may be used in the central pattern generator of biological system are induced
by collective integration of the NST element.Comment: 13 pages, 4 figure
Stability and Formation of the Resonant System HD 73526
Based on radial velocity measurements it has been found recently that the two
giant planets detected around the star HD 73526 are in 2:1 resonance. However,
as our numerical integration shows, the derived orbital data for this system
result in chaotic behavior of the giant planets, which is uncommon among the
resonant extrasolar planetary systems.
We intend to present regular (non-chaotic) orbital solutions for the giant
planets in the system HD 73526 and offer formation scenarios based on combining
planetary migration and sudden perturbative effects such as planet-planet
scattering or rapid dispersal of the protoplanetary disk. A comparison with the
already studied resonant system HD 128311, exhibiting similar behavior, is also
done.
The new sets of orbital solutions have been derived by the Systemic Console
(www.oklo.org). The stability of these solutions has been investigated by the
Relative Lyapunov indicator, while the migration and scattering effects are
studied by gravitational N-body simulations applying non-conservative forces as
well. Additionally, hydrodynamic simulations of embedded planets in
protoplanetary disks are performed to follow the capture into resonance.
For the system HD 73526 we demonstrate that the observational radial velocity
data are consistent with a coplanar planetary system engaged in a stable 2:1
resonance exhibiting apsidal corotation. We have shown that, similarly to the
system HD 128311, the present dynamical state of HD 73526 could be the result
of a mixed evolutionary process melting together planetary migration and a
perturbative event.Comment: 12 pages, 14 figures, accepted in A&A, v2: technical change
Suppression of growth by multiplicative white noise in a parametric resonant system
The author studied the growth of the amplitude in a Mathieu-like equation
with multiplicative white noise. The approximate value of the exponent at the
extremum on parametric resonance regions was obtained theoretically by
introducing the width of time interval, and the exponents were calculated
numerically by solving the stochastic differential equations by a symplectic
numerical method. The Mathieu-like equation contains a parameter that
is determined by the intensity of noise and the strength of the coupling
between the variable and the noise. The value of was restricted not to
be negative without loss of generality. It was shown that the exponent
decreases with , reaches a minimum and increases after that. It was
also found that the exponent as a function of has only one minimum at
on parametric resonance regions of . This minimum
value is obtained theoretically and numerically. The existence of the minimum
at indicates the suppression of the growth by multiplicative
white noise.Comment: The title and the description in the manuscript are change
Resonant dynamics and the instability of anti-de Sitter spacetime
We consider spherically symmetric Einstein-massless-scalar field equations
with negative cosmological constant in five dimensions and analyze evolution of
small perturbations of anti-de Sitter spacetime using the recently proposed
resonant approximation. We show that for typical initial data the solution of
the resonant system develops an oscillatory singularity in finite time. This
result hints at a possible route to establishing instability of AdS under
arbitrarily small perturbations.Comment: 5 pages, 7 figure
A nonrelativistic limit for AdS perturbations
The familiar nonrelativistic limit converts the
Klein-Gordon equation in Minkowski spacetime to the free Schroedinger equation,
and the Einstein-massive-scalar system without a cosmological constant to the
Schroedinger-Newton (SN) equation. In this paper, motivated by the problem of
stability of Anti-de Sitter (AdS) spacetime, we examine how this limit is
affected by the presence of a negative cosmological constant .
Assuming for consistency that the product tends to a negative
constant as , we show that the corresponding
nonrelativistic limit is given by the SN system with an external harmonic
potential which we call the Schrodinger-Newton-Hooke (SNH) system. We then
derive the resonant approximation which captures the dynamics of small
amplitude spherically symmetric solutions of the SNH system. This resonant
system turns out to be much simpler than its general-relativistic version,
which makes it amenable to analytic methods. Specifically, in four spatial
dimensions, we show that the resonant system possesses a three-dimensional
invariant subspace on which the dynamics is completely integrable and hence can
be solved analytically. The evolution of the two-lowest-mode initial data (an
extensively studied case for the original general-relativistic system), in
particular, is described by this family of solutions.Comment: v3: slightly expanded published versio
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