98 research outputs found
Three-dimensional black holes from deformed anti-de Sitter
We present new exact three-dimensional black-string backgrounds, which
contain both NS--NS and electromagnetic fields, and generalize the BTZ black
holes and the black string studied by Horne and Horowitz. They are obtained as
deformations of the Sl(2,R) WZW model. Black holes resulting from purely
continuous deformations possess true curvature singularities. When discrete
identifications are introduced, extra chronological singularities appear, which
under certain circumstances turn out to be naked. The backgrounds at hand
appear in the moduli space of the Sl(2,R) WZW model. Hence, they provide exact
string backgrounds and allow for a more algebraical CFT description. This makes
possible the determination of the spectrum of primaries.Comment: JHEP style, 33 pages, 1 figur
Generalized instantons in N = 4 super Yang-Mills theory and spinorial geometry
Using spinorial geometry techniques, we classify the supersymmetric solutions
of euclidean super Yang-Mills theory. These backgrounds represent
generalizations of instantons with nontrivial scalar fields turned on, and
satisfy some constraints that bear a similarity with the Hitchin equations, and
contain the Donaldson equations as a special subcase. It turns out that these
constraints can be obtained by dimensional reduction of the octonionic
instanton equations, and may be rephrased in terms of a selfduality-like
condition for a complex connection. We also show that the supersymmetry
conditions imply the equations of motion only partially.Comment: 29 pages, 3 tables. v2: references added. v3: conclusion extended,
version published in JHE
Fracture Propagation Driven by Fluid Outflow from a Low-permeability Aquifer
Deep saline aquifers are promising geological reservoirs for CO2
sequestration if they do not leak. The absence of leakage is provided by the
caprock integrity. However, CO2 injection operations may change the
geomechanical stresses and cause fracturing of the caprock. We present a model
for the propagation of a fracture in the caprock driven by the outflow of fluid
from a low-permeability aquifer. We show that to describe the fracture
propagation, it is necessary to solve the pressure diffusion problem in the
aquifer. We solve the problem numerically for the two-dimensional domain and
show that, after a relatively short time, the solution is close to that of
one-dimensional problem, which can be solved analytically. We use the relations
derived in the hydraulic fracture literature to relate the the width of the
fracture to its length and the flux into it, which allows us to obtain an
analytical expression for the fracture length as a function of time. Using
these results we predict the propagation of a hypothetical fracture at the In
Salah CO2 injection site to be as fast as a typical hydraulic fracture. We also
show that the hydrostatic and geostatic effects cause the increase of the
driving force for the fracture propagation and, therefore, our solution serves
as an estimate from below. Numerical estimates show that if a fracture appears,
it is likely that it will become a pathway for CO2 leakage.Comment: 21 page
The Spectrum of Strings on Warped AdS_3 x S^3
String theory on NS-NS AdS_3 x S^3 admits an exactly marginal deformation
which breaks the SL(2,R)_R x SL(2,R)_L isometry of AdS_3 down to SL(2,R)_R x
U(1)_L. The holographic dual is an exotic and only partially understood type of
two-dimensional CFT with a reduced unbroken global conformal symmetry group. In
this paper we study the deformed theory on the string worldsheet. It is found
to be related by a spectral flow which is nonlocal in spacetime to the
undeformed worldsheet theory. An exact formula for the spectrum of massive
strings is presented.Comment: 26 pages, no figure
The classical origin of quantum affine algebra in squashed sigma models
We consider a quantum affine algebra realized in two-dimensional non-linear
sigma models with target space three-dimensional squashed sphere. Its affine
generators are explicitly constructed and the Poisson brackets are computed.
The defining relations of quantum affine algebra in the sense of the Drinfeld
first realization are satisfied at classical level. The relation to the
Drinfeld second realization is also discussed including higher conserved
charges. Finally we comment on a semiclassical limit of quantum affine algebra
at quantum level.Comment: 25 pages, 2 figure
Yet Another Realization of Kerr/CFT Correspondence
The correspondence between the Kerr black hole and a boundary CFT has been
conjectured recently. The conjecture has been proposed first only for the half
of the CFT, namely for left movers. For right movers, the correspondence has
been also found out through the suitable asymptotic boundary condition.
However, the boundary conditions for these two studies are exclusive to each
other. The boundary condition for left movers does not allow the symmetry of
right movers, and vice versa. We propose new boundary condition which allows
both of left and right movers.Comment: 6 pages, references adde
String Theory on Warped AdS_3 and Virasoro Resonances
We investigate aspects of holographic duals to time-like warped AdS_3
space-times--which include G\"odel's universe--in string theory. Using
worldsheet techniques similar to those that have been applied to AdS_3
backgrounds, we are able to identify space-time symmetry algebras that act on
the dual boundary theory. In particular, we always find at least one Virasoro
algebra with computable central charge. Interestingly, there exists a dense set
of points in the moduli space of these models in which there is actually a
second commuting Virasoro algebra, typically with different central charge than
the first. We analyze the supersymmetry of the backgrounds, finding related
enhancements, and comment on possible interpretations of these results. We also
perform an asymptotic symmetry analysis at the level of supergravity, providing
additional support for the worldsheet analysis.Comment: 24 pages + appendice
Cardy and Kerr
The Kerr/CFT correspondence employs the Cardy formula to compute the entropy
of the left moving CFT states. This computation, which correctly reproduces the
Bekenstein--Hawking entropy of the four-dimensional extremal Kerr black hole,
is performed in a regime where the temperature is of order unity rather than in
a high-temperature regime. We show that the comparison of the entropy of the
extreme Kerr black hole and the entropy in the CFT can be understood within the
Cardy regime by considering a D0-D6 system with the same entropic properties.Comment: 20 pages; LaTeX; JHEP format; v.2 references added, v.3 Section 4
adde
Warped AdS3/Dipole-CFT Duality
String theory contains solutions with SL(2,R)_R x U(1)_L-invariant warped
AdS3 (WAdS3) factors arising as continuous deformations of ordinary AdS3
factors. We propose that some of these are holographically dual to the IR
limits of nonlocal dipole-deformed 2D D-brane gauge theories, referred to as
"dipole CFTs". Neither the bulk nor boundary theories are currently
well-understood, and consequences of the proposed duality for both sides is
investigated. The bulk entropy-area law suggests that dipole CFTs have (at
large N) a high-energy density of states which does not depend on the
deformation parameter. Putting the boundary theory on a spatial circle leads to
closed timelike curves in the bulk, suggesting a relation of the latter to
dipole-type nonlocality.Comment: 13 page
Clinical inertia in general practice:widespread and related to the outcome of diabetes care
Materials and methods. Baseline and follow-up data of a Dutch randomized controlled trial on the implementation of a locally adapted guideline were used. The study involved 30 general practices and 1283 patients. Treatment targets differed between study groups [HbA1c <8.0% and blood pressure (BP) <140/85% versus HbA1c <8.5% and BP <150/85]. Clinical inertia was defined as the failure to intensify therapy when indicated. A complete medication profile of all participating patients was obtained. Results. In the intervention and control group, the percentages of patients with poor diabetes or lipid control who did not receive treatment intensification were 45% and 90%, approximately. More control group patients with BP levels above target were confronted with inertia (72.7% versus 63.3%, P <0.05). In poorly controlled hypertensive patients, inertia was associated with the height of systolic BP at baseline [adjusted odds ratio (OR) 0.98, 95% confidence interval (CI) 0.98-0.99] and the frequency of BP control (adjusted OR 0.89, 95% CI 0.81-0.99). If a practice nurse managed these patients, clinical inertia was less common (adjusted OR 0.12, 95% CI 0.02-0.91). In both study groups, cholesterol decreased significantly more in patients who received proper treatment intensification. Conclusion. GPs were more inclined to control blood glucose levels than BP or cholesterol levels. Inertia in response to poorly controlled high BP was less common if nurses assisted GPs
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