12,428 research outputs found
Charged Rotating Black Hole Formation from Thin Shell Collapse in Three Dimensions
The thin shell collapse leading to the formation of charged rotating black
holes in three dimensions is analyzed in the light of a recently developed
Hamiltonian formalism for these systems. It is proposed to demand, as a way to
reconcile the properties of an infinitely extended solenoid in flat space with
a magnetic black hole in three dimensions, that the magnetic field should
vanish just outside the shell. The adoption of this boundary condition results
in an exterior solution with a magnetic field different from zero at a finite
distance from the shell. The interior solution is also found and assigns
another interpretation, in a different context, to the magnetic solution
previously obtained by Cl\'{e}ment and by Hirschmann and Welch.Comment: 15 pages, no figures. Discussion on junction conditions and
conclusions enlarged. Few references added. Final version for MPL
Exact Renormalization of Massless QED2
We perform the exact renormalization of two-dimensional massless gauge
theories. Using these exact results we discuss the cluster property and
confinement in both the anomalous and chiral Schwinger models.Comment: 14 pages, no figures, introduction and conclusions modifie
Suppression of viscous fluid fingering: a piecewise constant-injection process
The injection of a fluid into another of larger viscosity in a Hele-Shaw cell
usually results in the formation of highly branched patterns. Despite the
richness of these structures, in many practical situations such convoluted
shapes are quite undesirable. In this letter we propose an efficient and easily
reproducible way to restrain these instabilities based on a simple piecewise
constant pumping protocol. It results in a reduction in the size of the viscous
fingers by one order of magnitude.Comment: Published in Phys. Rev.
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