1,079 research outputs found
Stability of a hot two-temperature accretion disc with advection
The effects of radial advection and thermal diffusion were considered in
investigating the linear stability of an optically thin, two-temperature
accretion disc. If the disc has only very little advection, we proved that the
thermal instability exists when the disc is geometrically thin. But it dispears
in a geometrically slim disc if the thermal diffusion was considered. Moreover,
if the disc is advection dominated, the thermal instability does not exist. In
addition, we found that the instabilities of inertial-acoustic modes exist only
in a geometrically thin disc or an advection-dominated disc with low Mach
number, whereas the Lightman & Eardley viscous instability always dispears in a
two-temperature disc. A simple comparison also showed that an optically thin,
bremsstrahlung cooling dominated disc is generally more thermally unstable than
a two-temperature disc if it is not advection-dominated.Comment: 12 pages, LaTeX file, 3 figures, accepted for publication in MNRAS.
Revised with a few important references added and several inaccurate
references correcte
Instability of the solitary waves for the generalized Boussinesq equations
In this work, we consider the following generalized Boussinesq equation
\begin{align*}
\partial_{t}^2u-\partial_{x}^2u+\partial_{x}^2(\partial_{x}^2u+|u|^{p}u)=0,\qquad
(t,x)\in\mathbb R\times \mathbb R, \end{align*} with . This
equation has the traveling wave solutions , with the
frequency and satisfying \begin{align*}
-\partial_{xx}{\phi}_{\omega}+(1-{\omega^2}){\phi}_{\omega}-{\phi}_{\omega}^{p+1}=0.
\end{align*} Bona and Sachs (1988) proved that the traveling wave
is orbitally stable when . Liu (1993) proved the orbital instability under the conditions
or . In this paper, we prove
the orbital instability in the degenerate case .Comment: 29 page
Possible High-Energy Neutrino and Photon Signals from Gravitational Wave Bursts due to Double Neutron Star Mergers
As the technology of gravitational-wave and neutrino detectors becomes
increasingly mature, a multi-messenger era of astronomy is ushered in. Advanced
gravitational wave detectors are close to making a ground-breaking discovery of
gravitational wave bursts (GWBs) associated with mergers of double neutron
stars (NS-NS). It is essential to study the possible electromagnetic (EM) and
neutrino emission counterparts of these GWBs. Recent observations and numerical
simulations suggest that at least a fraction of NS-NS mergers may leave behind
a massive millisecond magnetar as the merger product. Here we show that protons
accelerated in the forward shock powered by a magnetar wind pushing the ejecta
launched during the merger process would interact with photons generated in the
dissipating magnetar wind and emit high energy neutrinos and photons. We
estimate the typical energy and fluence of the neutrinos from such a scenario.
We find that PeV neutrinos could be emitted from the shock front as long
as the ejecta could be accelerated to a relativistic speed. The diffuse
neutrino flux from these events, even under the most optimistic scenarios, is
too low to account for the two events announced by the IceCube Collaboration,
but it is only slightly lower than the diffuse flux of GRBs, making it an
important candidate for the diffuse background of PeV neutrinos. The
neutron-pion decay of these events make them a moderate contributor to the
sub-TeV gamma-ray diffuse background.Comment: Accepted for publication in PRD, minor revisio
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