2,816 research outputs found
Fluid accretion onto a spherical black hole: relativistic description versus Bondi model
We describe general-relativistically a spherically symmetric stationary fluid
accretion onto a black hole. Relativistic effects enhance mass accretion, in
comparison to the Bondi model predictions, in the case when backreaction is
neglected. That enhancement depends on the adiabatic index and the asymptotic
gas temperature and it can magnify accretion by one order in the
ultrarelativistic regime.Comment: 22 pages, accepted by the Physical Review
Gravitational redshifts in electromagnetic bursts occuring near Schwarzschild horizon
It was suggested earlier that the gravitational redshift formula can be
invalid when the effect of the backscattering is strong. It is demonstrated
here numerically, for an exemplary electromagnetic pulse that is: i) initially
located very close to the horizon of a Schwarzschild black hole and ii)
strongly backscattered, that a mean frequency does not obey the standard
redshift formula. Redshifts appear to depend on the frequency and there
manifests a backscatter-induced blueshift in the outgoing radiation.Comment: 4 pages, 2 figures. To appear in the Class. Q. Gra
Brown-York mass and the hoop conjecture in non-spherical massive systems
We discuss the relation between the concentration of the Brown-York mass and
the formation of trapped surfaces in non-spherical massive systems. In
particular, we formulate and prove a precise version of the Thorne hoop
conjecture in conformally flat three-geometries sliced by equipotential
foliation leaves. An intriguing relationship between the total rest mass and
the Brown-York mass is shown. This is a further investigation of the previous
work on the Brown-York mass hoop conjecture in spherical symmetry
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