3,367 research outputs found
Toward a Deterministic Model of Planetary Formation VII: Eccentricity Distribution of Gas Giants
The ubiquity of planets and diversity of planetary systems reveal planet
formation encompass many complex and competing processes. In this series of
papers, we develop and upgrade a population synthesis model as a tool to
identify the dominant physical effects and to calibrate the range of physical
conditions. Recent planet searches leads to the discovery of many
multiple-planet systems. Any theoretical models of their origins must take into
account dynamical interaction between emerging protoplanets. Here, we introduce
a prescription to approximate the close encounters between multiple planets. We
apply this method to simulate the growth, migration, and dynamical interaction
of planetary systems. Our models show that in relatively massive disks, several
gas giants and rocky/icy planets emerge, migrate, and undergo dynamical
instability. Secular perturbation between planets leads to orbital crossings,
eccentricity excitation, and planetary ejection. In disks with modest masses,
two or less gas giants form with multiple super-Earths. Orbital stability in
these systems is generally maintained and they retain the kinematic structure
after gas in their natal disks is depleted. These results reproduce the
observed planetary mass-eccentricity and semimajor axis-eccentricity
correlations. They also suggest that emerging gas giants can scatter residual
cores to the outer disk regions. Subsequent in situ gas accretion onto these
cores can lead to the formation of distant (> 30AU) gas giants with nearly
circular orbits.Comment: 54 pages, 14 Figures; accepted for publication in Astrophysical
Journa
Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
We have investigated the formation of close-in extrasolar giant planets
through a coupling effect of mutual scattering, Kozai mechanism, and tidal
circularization, by orbital integrations. We have carried out orbital
integrations of three planets with Jupiter-mass, directly including the effect
of tidal circularization. We have found that in about 30% runs close-in planets
are formed, which is much higher than suggested by previous studies. We have
found that Kozai mechanism by outer planets is responsible for the formation of
close-in planets. During the three-planet orbital crossing, the Kozai
excitation is repeated and the eccentricity is often increased secularly to
values close enough to unity for tidal circularization to transform the inner
planet to a close-in planet. Since a moderate eccentricity can remain for the
close-in planet, this mechanism may account for the observed close-in planets
with moderate eccentricities and without nearby secondary planets. Since these
planets also remain a broad range of orbital inclinations (even retrograde
ones), the contribution of this process would be clarified by more observations
of Rossiter-McLaughlin effects for transiting planets.Comment: 15 pages, 16 figures, Accepted for publication in Ap
Supersymmetry in gauge theories with extra dimensions
We show that a quantum-mechanical N=2 supersymmetry is hidden in 4d mass
spectrum of any gauge invariant theories with extra dimensions. The N=2
supercharges are explicitly constructed in terms of differential forms. The
analysis can be extended to extra dimensions with boundaries, and for a single
extra dimension we clarify a possible set of boundary conditions consistent
with 5d gauge invariance, although some of the boundary conditions break 4d
gauge symmetries.Comment: 18 page
Extended supersymmetry and its reduction on a circle with point singularities
We investigate -extended supersymmetry in one-dimensional quantum
mechanics on a circle with point singularities. For any integer ,
supercharges are explicitly constructed in terms of discrete transformations,
and a class of singularities compatible with supersymmetry is clarified. In our
formulation, the supersymmetry can be reduced to -extended supersymmetry for
any integer . The degeneracy of the spectrum and spontaneous supersymmetry
breaking are also studied.Comment: 36 pages, 5 figures, 2 table
Axions from wall decay
We discuss the decay of axion walls bounded by strings and present numerical
simulations of the decay process. In these simulations, the decay happens
immediately, in a time scale of order the light travel time, and the average
energy of the radiated axions is for . is found to increase approximately linearly with
. Extrapolation of this behaviour yields in axion models of interest.Comment: 6 pages, 7 figures, to be published in the Proc. of the 5th IFT Axion
workshop Gainesville FL, Mar 13-15 199
Gauge-Fixing and Residual Symmetries in Gauge/Gravity Theories with Extra Dimensions
We study compactified pure gauge/gravitational theories with gauge-fixing
terms and show that these theories possess quantum mechanical SUSY-like
symmetries between unphysical degrees of freedom. These residual symmetries are
global symmetries and generated by quantum mechanical N=2 supercharges. Also,
we establish new one-parameter family of gauge choices for higher-dimensional
gravity, and calculate as a check of its validity one graviton exchange
amplitude in the lowest tree-level approximation. We confirm that the result is
indeed -independent and the cancellation of the -dependence is
ensured by the residual symmetries. We also give a simple interpretation of the
vDVZ-discontinuity, which arises in the lowest tree-level approximation, from
the supersymmetric point of view.Comment: REVTeX4, 17 pages, 1 figur
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