981 research outputs found
Comment on ``Absence of abelian Higgs hair for extremal black holes''
We examine the claim of Chamblin et. al. that extreme black holes cannot
support abelian Higgs hair. We provide evidence that contradicts this claim and
discuss reasons for this discrepancy.Comment: 1 page 2 figures, revised titl
Riggs on strong justification
In 'The Weakness of Strong Justification' Wayne Riggs claims that the requirement that justified beliefs be truth conducive (likely to be true) is not always compatible with the requirement that they be epistemically responsible (arrived at in an epistemically responsible manner)1. He supports this claim by criticising Alvin Goldman's view that if a belief is strongly justified, it is also epistemically responsible. In light of this, Riggs recommends that we develop two independent conceptions of justification, one that insists upon the requirement that beliefs be truth conducive and another that insists that they be epistemically responsible. It will then, on his view, be possible to properly evaluate beliefs with regard to each conception of justification. Riggs, however, is mistaken in supposing that the two epistemic requirements are independent. If a belief is responsibly arrived at, it is therefore likely to be true. He is thus also mistaken in supposing that the two epistemic requirements are incompatible. This mistake arises because Riggs assumes that justification is possible or, at least, that it involves standards that are akin to our own. Moreover, once this assumption is made explicit, we can see why a notion of justification that connects epistemic practice with likely truth is significant
Abelian Higgs Hair for Rotating and Charged Black Holes
We study the problem of vortex solutions in the background of rotating black
holes in both asymptotically flat and asymptoticlly anti de Sitter spacetimes.
We demonstrate the Abelian Higgs field equations in the background of four
dimensional Kerr, Kerr-AdS and Reissner-Nordstrom-AdS black holes have vortex
line solutions. These solutions, which have axial symmetry, are generalization
of the Nielsen-Olesen string. By numerically solving the field equations in
each case, we find that these black holes can support an Abelian Higgs field as
hair. This situation holds even in the extremal case, and no flux-expulsion
occurs. We also compute the effect of the self gravity of the Abelian Higgs
field show that the the vortex induces a deficit angle in the corresponding
black hole metrics.Comment: 22 pages, 16 figures, a section about the vortex self gravity on Kerr
black hole added, extremal black holes considered, one figure changed, one
reference adde
Thick domain wall universes
We investigate the spacetime of a thick gravitating domain wall for a general
potential . Using general analytical arguments we show that all
nontrivial solutions fall into two categories: those interpretable as an
isolated domain wall with a cosmological event horizon, and those which are
pure false vacuum de Sitter solutions. Although this latter solution is always
unstable to the field rolling coherently to its true vacuum, we show that there
is an additional instability to wall formation if the scalar field does not
couple too strongly to gravity. Using the and sine-Gordon
models as illustrative examples, we investigate the phase space of the
gravitating domain wall in detail numerically, following the solutions from
weak to strong gravity. We find excellent agreement with the analytic work.
Then, we analyse the domain wall in the presence of a cosmological constant
finding again the two kinds of solutions, wall and de Sitter, even in the
presence of a negative cosmological constant.Comment: 20 pages revtex, epsfig, references added, some conclusions altere
Abelian Higgs Hair for a Static Charged Black String
We study the problem of vortex solutions in the background of an electrically
charged black string. We show numerically that the Abelian Higgs field
equations in the background of a four-dimensional black string have vortex
solutions. These solutions which have axial symmetry, show that the black
string can support the Abelian Higgs field as hair. This situation holds also
in the case of the extremal black string. We also consider the self-gravity of
the Abelian Higgs field and show that the effect of the vortex is to induce a
deficit angle in the metric under consideration.Comment: REVTEX4, 12 pages, 6 figures, The version to be appeared in Phys.
Rev.
Hairy rotating black string in the Einstein-Maxwell-Higgs system
We show numerically that the Abelian Higgs field equations in the background
of a four-dimensional rotating charged black string have vortex solutions.
These solutions which have axial symmetry show that the rotating black string
can support the Abelian Higgs field as hair. We find that one encounters with
an electric field coupled to the Higgs scalar field for the case of rotating
black string. This electric field is due to an electric charge per unit length,
which increases as the rotation parameter becomes larger. We also find that the
vortex thickness decreases as the rotation parameter grows up. Finally we
consider the self-gravity of the Abelian Higgs field and show that the effect
of the vortex is to induce a deficit angle in the metric under consideration
which decreases as the rotation parameter increases.Comment: 16 pages, 8 figures, references added, some minor corrections don
ADH Levels during Salt Depletion in Dogs *
Two groups of trained dogs were subjected to sodium chloride depletion and plasma ADH concentration, renin activity, plasma sodium, plasma osmolality, blood volume, hematocrit and body weight were measured. In one group of animals, sodium depletion was created by restricting intake to 5 mEq/24 h. Despite a statistically significant decrease in body weight and blood volume and a corresponding increase in plasma renin activity, plasma ADH concentration was not seen to change significantly from control values. Similar findings were seen in a second group of dogs which were given a diuretic in addition to dietary sodium restriction. In these animals the decrease in blood volume and rise in plasma renin activity were proportionately greater. Plasma ADH concentration was not observed to change significantly in this group of animals either. Both groups of animals developed significant hyponatremia during the experiment. It is concluded that in these dogs, the secretion of ADH was not suppressed and consequently hyponatremia developed. It is suggested that endogenous angiotensin was responsible for the continued secretion of ADH at control levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75034/1/j.1365-2362.1971.tb00567.x.pd
Analytic continuations of de Sitter thick domain wall solutions
We perform some analytic continuations of the de Sitter thick domain wall
solutions obtained in our previous paper hep-th/0201130 in the system of
gravity and a scalar field with an axion-like potential. The obtained new
solutions represent anti-de Sitter thick domain walls and cosmology. The
anti-de Sitter domain wall solutions are periodic, and correspondingly the
cosmological solutions represent cyclic universes. We parameterize the
axion-like scalar field potential and determine the parameter regions of each
type of solutions.Comment: Additons in section 5, 8 pages, 7 figures, RevTe
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