7,698 research outputs found
The Limit of the Boltzmann Equation to the Euler Equations for Riemann Problems
The convergence of the Boltzmann equaiton to the compressible Euler equations
when the Knudsen number tends to zero has been a long standing open problem in
the kinetic theory. In the setting of Riemann solution that contains the
generic superposition of shock, rarefaction wave and contact discontinuity to
the Euler equations, we succeed in justifying this limit by introducing
hyperbolic waves with different solution backgrounds to capture the extra
masses carried by the hyperbolic approximation of the rarefaction wave and the
diffusion approximation of contact discontinuity.Comment: 59 page
Magnetic Coupling of a Rotating Black Hole with Advection-Dominated Accretion Flows
A model of magnetic coupling (MC) of a rotating black hole (BH) with
advection- dominated accretion flow (MCADAF) is proposed. It turns out that
MCADAF providers a natural explanation for the transition radius between ADAF
and SSD, and could be used to interpret the highest luminosity of GX 339-4 in
hard-state. A very steep emissivity index can be produced in the innermost part
of the MCADAF,which is consistent with the recent XMM-Newton observations of
the nearby bright Seyfert 1 galaxy MCG-6-30-15 and with two X-ray binaries
(XRBs): XTE J1655-500 and GX 339-4. In addition, we estimate the BH spins in
Seyfert 1 galaxy MCG-6-30-15 and in the two XRBs based on this model.Comment: 18 pages, 9 figures,acceptted by New Astronom
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