53 research outputs found
The possible role of r-modes in post-glitch relaxation of Crab
The loss of angular momentum through gravitational radiation, driven by the
excitation of r-modes, is considered in neutron stars having rotation
frequencies smaller than the associated critical frequency. We find that for
reasonable values of the initial amplitudes of such pulsation modes of the
star, being excited at the event of a glitch in a pulsar, the total post-glitch
losses correspond to a negligible fraction of the initial rise of the spin
frequency in the case of Vela and the older pulsars. However, for the Crab
pulsar the same effect would result, within a few months, in a decrease in its
spin frequency by an amount larger than its glitch-induced frequency increase.
This could provide an explanation for the peculiar behavior observed in the
post-glitch relaxations of the Crab.Comment: 9 pages, 4 figures, RevTe
A Comparison between Real and DLA Simulated Liver Lobules using a Population Density Analysis
A liver lobule is comprised of networks of sinusoids and hepatocytes. Here, a liver lobule was computationally constructed by using diffusion-limited aggregation (DLA) method. A population density analysis of the sinusoids and hepatocytes was performed and then compared with a real lobule image. The resulting images were compared using a histogram to interpret the ratio of hepatocytes to sinusoids
Black holes on the brane
We consider exact solutions for static black holes localized on a three-brane
in five-dimensional gravity in the Randall-Sundrum scenario. We show that the
Reissner-Nordstrom metric is an exact solution of the effective Einstein
equations on the brane, re-interpreted as a black hole without electric charge,
but with instead a tidal 'charge' arising via gravitational effects from the
fifth dimension. The tidal correction to the Schwarzschild potential is
negative, which is impossible in general relativity, and in this case only one
horizon is admitted, located outside the Schwarzschild horizon. The solution
satisfies a closed system of equations on the brane, and describes the
strong-gravity regime. Current observations do not strongly constrain the tidal
charge, and significant tidal corrections could in principle arise in the
strong-gravity regime and for primordial black holes.Comment: 5 pages Revtex. v2: Expanded discussion, minor corrections,
additional references. v3: Improved discussion of black hole properties.
Version to appear in Phys. Lett.
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