41 research outputs found
The Axisymmetric Case for the Post-Newtonian Dedekind Ellipsoids
We consider the post-Newtonian approximation for the Dedekind ellipsoids in
the case of axisymmetry. The approach taken by Chandrasekhar & Elbert (1974,
1978) excludes the possibility of finding a uniformly rotating (deformed)
spheroid in the axially symmetric limit, though the solution exists at the
point of axisymmetry. We consider an extension to their work that permits the
possibility of such a limit.Comment: 12 pages, v1: more discussion of comparison to Chandrasekhar's and
Elbert's work, modified to agree with published versio
The Meissner effect for weakly isolated horizons
Black holes are important astrophysical objects describing an end state of
stellar evolution, which are observed frequently. There are theoretical
predictions that Kerr black holes with high spins expel magnetic fields.
However, Kerr black holes are pure vacuum solutions, which do not include
accretion disks, and additionally previous investigations are mainly limited to
weak magnetic fields. We prove for the first time in full general relativity
that generic rapidly spinning black holes including those deformed by accretion
disks still expel even strong magnetic fields. Analogously to a similar
property of superconductors, this is called Meissner effect.Comment: 7 pages, 4 figure
The Meissner Effect for axially symmetric charged black holes
In our previous work [N. G\"urlebeck, M. Scholtz, Phys. Rev. D 95 064010
(2017)], we have shown that electric and magnetic fields are expelled from the
horizons of extremal, stationary and axially symmetric uncharged black holes;
this is called the Meissner effect for black holes. Here, we generalize this
result in several directions. First, we allow that the black hole carries
charge, which requires a generalization of the definition of the Meissner
effect.
Next, we introduce the notion of almost isolated horizons, which is weaker
than the usual notion of isolated horizons, since the geometry of the former is
not necessarily completely time-independent. Moreover, we allow the horizon to
be pierced by strings, thereby violating the usual assumption on the spherical
topology made in the definition of the weakly isolated horizon. Finally, we
spell out in detail all assumptions entering the proof and show that the
Meissner effect is an inherent property of black holes even in full non-linear
theory.Comment: 11 page