29,017 research outputs found
High energy neutrino early afterglows from gamma-ray bursts revisited
The high energy neutrino emission from gamma-ray bursts (GRBs) has been
expected in various scenarios. In this paper, we study the neutrino emission
from early afterglows of GRBs, especially under the reverse-forward shock model
and late prompt emission model. In the former model, the early afterglow
emission occurs due to dissipation made by an external shock with the
circumburst medium (CBM). In the latter model, internal dissipation such as
internal shocks produces the shallow decay emission in early afterglows. We
also discuss implications of recent Swift observations for neutrino signals in
detail. Future neutrino detectors such as IceCube may detect neutrino signals
from early afterglows, especially under the late prompt emission model, while
the detection would be difficult under the reverse-forward shock model.
Contribution to the neutrino background from the early afterglow emission may
be at most comparable to that from the prompt emission unless the outflow
making the early afterglow emission loads more nonthermal protons, and it may
be important in the very high energies. Neutrino-detections are inviting
because they could provide us with not only information on baryon acceleration
but also one of the clues to the model of early afterglows. Finally, we compare
various predictions for the neutrino background from GRBs, which are testable
by future neutrino-observations.Comment: 18 pages, 12 figures, accepted for publication in PR
Luminosity of young Jupiters revisited. Massive cores make hot planets
The intrinsic luminosity of young Jupiters is of high interest for planet
formation theory. It is an observable quantity that is determined by important
physical mechanisms during formation, namely the accretion shock structure, and
even more fundamentally, the basic formation mechanism (core accretion or
gravitational instability). We study the impact of the core mass on the
post-formation entropy and luminosity of young giant planets forming via core
accretion with a supercritical shock (cold accretion). For this, we conduct
self-consistently coupled formation and evolution calculations of giant planets
with masses between 1 and 12 Jovian masses and core masses between 20 and 120
Earth masses. We find that the post-formation luminosity of massive giant
planets is very sensitive to the core mass. An increase of the core mass by a
factor 6 results in an increase of the post-formation luminosity of a 10 Jovian
mass planet by a factor 120. Due to this dependency, there is no single well
defined post-formation luminosity for core accretion, but a wide range. For
massive cores (~100 Earth masses), the post-formation luminosities of core
accretion planets become so high that they approach those in the hot start
scenario that is often associated with gravitational instability. For the
mechanism to work, it is necessary that the solids are accreted before or
during gas runaway accretion, and that they sink deep into the planet. We make
no claims whether or not such massive cores can actually form in giant planets.
But if yes, it becomes difficult to rule out core accretion as formation
mechanism based solely on luminosity for directly imaged planets that are more
luminous than predicted for low core masses. Instead of invoking gravitational
instability as the consequently necessary formation mode, the high luminosity
could also be caused simply by a more massive core.Comment: 11 pages, 6 figures. A&A accepte
Exploring the correlation between the folding rates of proteins and the entanglement of their native states
The folding of a protein towards its native state is a rather complicated
process. However there are empirical evidences that the folding time correlates
with the contact order, a simple measure of the spatial organisation of the
native state of the protein. Contact order is related to the average length of
the main chain loops formed by amino acids which are in contact. Here we argue
that folding kinetics can be influenced also by the entanglement that loops may
undergo within the overall three dimensional protein structure. In order to
explore such possibility, we introduce a novel descriptor, which we call
"maximum intrachain contact entanglement". Specifically, we measure the maximum
Gaussian entanglement between any looped portion of a protein and any other
non-overlapping subchain of the same protein, which is easily computed by
discretized line integrals on the coordinates of the atoms. By
analyzing experimental data sets of two-state and multistate folders, we show
that also the new index is a good predictor of the folding rate. Moreover,
being only partially correlated with previous methods, it can be integrated
with them to yield more accurate predictions.Comment: 8 figures. v2: new titl
H\"older foliations, revisited
We investigate transverse H\"older regularity of some canonical leaf
conjugacies in partially hyperbolic dynamical systems and transverse H\"older
regularity of some invariant foliations. Our results validate claims made
elsewhere in the literature.Comment: 52 pages, to appear in Journal of Modern Dynamic
Phase-Induced (In)-Stability in Coupled Parametric Oscillators
We report results on a model of two coupled oscillators that undergo periodic
parametric modulations with a phase difference . Being to a large
extent analytically solvable, the model reveals a rich dependence of
the regions of parametric resonance. In particular, the intuitive notion that
anti-phase modulations are less prone to parametric resonance is confirmed for
sufficiently large coupling and damping. We also compare our results to a
recently reported mean field model of collective parametric instability,
showing that the two-oscillator model can capture much of the qualitative
behavior of the infinite system.Comment: 19 pages, 8 figures; a version with better quality figures can be
found in http://hypatia.ucsd.edu/~mauro/English/publications.htm
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