721 research outputs found
Resolving the Structure of Black Holes: Philosophizing with a Hammer
We give a broad conceptual review of what we have learned about black holes
and their microstate structure from the study of microstate geometries and
their string theory limits. We draw upon general relativity, supergravity,
string theory and holographic field theory to extract universal ideas and
structural features that we expect to be important in resolving the information
problem and understanding the microstate structure of Schwarzschild and Kerr
black holes. In particular, we emphasize two conceptually and physically
distinct ideas, with different underlying energy scales: a) the transition that
supports the microstate structure and prevents the formation of a horizon and
b) the representation of the detailed microstate structure itself in terms of
fluctuations around the transitioned state. We also show that the supergravity
mechanism that supports microstate geometries becomes, in the string theory
limit, either brane polarization or the excitation of non-Abelian degrees of
freedom. We thus argue that if any mechanism for supporting structure at the
horizon scale is to be given substance within string theory then it must be
some manifestation of microstate geometries.Comment: 32 pages + reference
Bubbling Supertubes and Foaming Black Holes
We construct smooth BPS three-charge geometries that resolve the zero-entropy
singularity of the U(1) x U(1) invariant black ring. This singularity is
resolved by a geometric transition that results in geometries without any
branes sources or singularities but with non-trivial topology. These geometries
are both ground states of the black ring, and non-trivial microstates of the
D1-D5-P system. We also find the form of the geometries that result from the
geometric transition of N zero-entropy black rings, and argue that, in general,
such geometries give a very large number of smooth bound-state three-charge
solutions, parameterized by 6N functions. The generic microstate solution is
specified by a four-dimensional hyper-Kahler geometry of a certain signature,
and contains a ``foam'' of non-trivial two-spheres. We conjecture that these
geometries will account for a significant part of the entropy of the D1-D5-P
black hole, and that Mathur's conjecture might reduce to counting certain
hyper-Kahler manifolds.Comment: 40 pages, harvmac. v2 references added, typo correcte
Almost BPS but still not renormalized
A key feature of BPS multi-center solutions is that the equations controlling
the positions of these centers are not renormalized as one goes from weak to
strong coupling. In particular, this means that brane probes can capture the
same information as the fully back-reacted supergravity solution. We
investigate this non-renormalization property for non-supersymmetric, extremal
"almost-BPS" solutions at intermediate coupling when one of the centers is
considered as a probe in the background created by the other centers. We find
that despite the lack of supersymmetry, the probe action reproduces exactly the
equations underlying the fully back-reacted solution, which indicates that
these equations also do not receive quantum corrections. In the course of our
investigation we uncover the relation between the charge parameters of
almost-BPS supergravity solutions and their quantized charges, which solves an
old puzzle about the quantization of the charges of almost-BPS solutions.Comment: 29 pages, 1 figur
The Foaming Three-Charge Black Hole
We find a very large set of smooth horizonless geometries that have the same
charges and angular momenta as the five-dimensional, maximally-spinning,
three-charge, BPS black hole (J^2 = Q^3). Our solutions are constructed using a
four-dimensional Gibbons-Hawking base space that has a very large number of
two-cycles. The entropy of our solutions is proportional to Q^(1/2). In the
same class of solutions we also find microstates corresponding to zero-entropy
black rings, and these are related to the microstates of the black hole by
continuous deformations.Comment: 14 pages, harvma
A geometric study of the dispersionless Boussinesq type equation
We discuss the dispersionless Boussinesq type equation, which is equivalent
to the Benney-Lax equation, being a system of equations of hydrodynamical type.
This equation was discussed in
. The results include: a
description of local and nonlocal Hamiltonian and symplectic structures,
hierarchies of symmetries, hierarchies of conservation laws, recursion
operators for symmetries and generating functions of conservation laws
(cosymmetries). Highly interesting are the appearances of operators that send
conservation laws and symmetries to each other but are neither Hamiltonian, nor
symplectic. These operators give rise to a noncommutative infinite-dimensional
algebra of recursion operators
The Long Term Stability of Oscillations During Thermonuclear X-ray Bursts: Constraining the Binary X-ray Mass Function
We report on the long term stability of the millisecond oscillations observed
with the Rossi X-ray Timing Explorer (RXTE) during thermonuclear X-ray bursts
from the low mass X-ray binaries (LMXB) 4U 1728-34 and 4U 1636-53. We show that
bursts from 4U 1728-34 spanning more than 1.5 years have observed asymptotic
oscillation periods which are within 0.2 microsec. of each other, well within
the magnitude which could be produced by the orbital motion of the neutron star
in a typical LMXB. This stability implies a timescale to change the oscillation
period of > 23,000 years, suggesting a highly stable process such as stellar
rotation as the oscillation mechanism. We show that period offsets in three
distinct bursts from 4U 1636-53 can be plausibly interpreted as due to orbital
motion of the neutron star in this 3.8 hour binary system. We discuss the
constraints on the mass function which can in principle be derived using this
technique.Comment: 11 pages, 4 figures. AASTeX, to be published in the Astrophysical
Journal Letter
Maternal antibodies from mothers of children with autism alter brain growth and social behavior development in the rhesus monkey.
Antibodies directed against fetal brain proteins of 37 and 73 kDa molecular weight are found in approximately 12% of mothers who have children with autism spectrum disorder (ASD), but not in mothers of typically developing children. This finding has raised the possibility that these immunoglobulin G (IgG) class antibodies cross the placenta during pregnancy and impact brain development, leading to one form of ASD. We evaluated the pathogenic potential of these antibodies by using a nonhuman primate model. IgG was isolated from mothers of children with ASD (IgG-ASD) and of typically developing children (IgG-CON). The purified IgG was administered to two groups of female rhesus monkeys (IgG-ASD; n=8 and IgG-CON; n=8) during the first and second trimesters of pregnancy. Another control group of pregnant monkeys (n=8) was untreated. Brain and behavioral development of the offspring were assessed for 2 years. Behavioral differences were first detected when the macaque mothers responded to their IgG-ASD offspring with heightened protectiveness during early development. As they matured, IgG-ASD offspring consistently deviated from species-typical social norms by more frequently approaching familiar peers. The increased approach was not reciprocated and did not lead to sustained social interactions. Even more striking, IgG-ASD offspring displayed inappropriate approach behavior to unfamiliar peers, clearly deviating from normal macaque social behavior. Longitudinal magnetic resonance imaging analyses revealed that male IgG-ASD offspring had enlarged brain volume compared with controls. White matter volume increases appeared to be driving the brain differences in the IgG-ASD offspring and these differences were most pronounced in the frontal lobes
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