4,075 research outputs found
Conformal Symmetry for General Black Holes
We show that the warp factor of a generic asymptotically flat black hole in
five dimensions can be adjusted such that a conformal symmetry emerges. The
construction preserves all near horizon properties of the black holes, such as
the thermodynamic potentials and the entropy. We interpret the geometry with
modified asymptotic behavior as the "bare" black hole, with the ambient flat
space removed. Our warp factor subtraction generalizes hidden conformal
symmetry and applies whether or not rotation is significant. We also find a
relation to standard AdS/CFT correspondence by embedding the black holes in six
dimensions. The asymptotic conformal symmetry guarantees a dual CFT description
of the general rotating black holes.Comment: 26 page
Ceramides: a new player in the inflammation-insulin resistance paradigm?
No abstract available
Measurement delay associated with the Guardian RT continuous glucose monitoring system.
AIMS: Using compartment modelling, we assessed the time delay between blood glucose and sensor glucose measured by the Guardian RT continuous glucose monitoring system in young subjects with Type 1 diabetes (T1D). METHODS: Twelve children and adolescents with T1D treated by continuous subcutaneous insulin infusion (male/female 7/5; age 13.1 +/- 4.2 years; body mass index 21.9 +/- 4.3 kg/m(2); mean +/- sd) were studied over 19 h in a Clinical Research Facility. Guardian RT was calibrated every 6 h and sensor glucose measured every 5 min. Reference blood glucose was measured every 15 min using a YSI 2300 STAT Plus Analyser. A population compartment model of sensor glucose-blood glucose kinetics was adopted to estimate the time delay, the calibration scale and the calibration shift. RESULTS: The population median of the time delay was 15.8 (interquartile range 15.2, 16.5) min, which was corroborated by correlation analysis between blood glucose and 15-min delayed sensor glucose. The delay has a relatively low intersubject variability, with 95% of individuals predicted to have delays between 10.4 and 24.3 min. Population medians (interquartile range) for the scale and shift are 0.800 (0.777, 0.823) (unitless) and 1.66 (1.47, 1.84) mmol/l, respectively. CONCLUSIONS: In young subjects with T1D, the total time delay associated with the Guardian RT system was approximately 15 min. This is twice that expected on physiological grounds, suggesting a 5- to 10-min delay because of data processing. Delays above 25 min are rarely to be observed
Separability of Black Holes in String Theory
We analyze the origin of separability for rotating black holes in string
theory, considering both massless and massive geodesic equations as well as the
corresponding wave equations. We construct a conformal Killing-Stackel tensor
for a general class of black holes with four independent charges, then identify
two-charge configurations where enhancement to an exact Killing-Stackel tensor
is possible. We show that further enhancement to a conserved Killing-Yano
tensor is possible only for the special case of Kerr-Newman black holes. We
construct natural null congruences for all these black holes and use the
results to show that only the Kerr-Newman black holes are algebraically special
in the sense of Petrov. Modifying the asymptotic behavior by the subtraction
procedure that induces an exact SL(2)^2 also preserves only the conformal
Killing-Stackel tensor. Similarly, we find that a rotating Kaluza-Klein black
hole possesses a conformal Killing-Stackel tensor but has no further
enhancements.Comment: 27 page
Active seismic studies in valley glacier settings: strategies and limitations
Subglacial tills play an important role in glacier dynamics but are difficult to characterize in situ. Amplitude Variation with Angle (AVA) analysis of seismic reflection data can distinguish between stiff tills and deformable tills. However, AVA analysis in mountain glacier environments can be problematic: reflections can be obscured by Rayleigh wave energy scattered from crevasses, and complex basal topography can impede the location of reflection points in 2-D acquisitions. We use a forward model to produce challenging synthetic seismic records in order to test the efficacy of AVA in crevassed and geometrically complex environments. We find that we can distinguish subglacial till types in moderately crevassed environments, where ‘moderate’ depends on crevasse spacing and orientation. The forward model serves as a planning tool, as it can predict AVA success or failure based on characteristics of the study glacier. Applying lessons from the forward model, we perform AVA on a seismic dataset collected from Taku Glacier in Southeast Alaska in March 2016. Taku Glacier is a valley glacier thought to overlay thick sediment deposits. A near-offset polarity reversal confirms that the tills are deformable
On graviton non-Gaussianities during inflation
We consider the most general three point function for gravitational waves
produced during a period of exactly de Sitter expansion. The de Sitter
isometries constrain the possible shapes to only three: two preserving parity
and one violating parity. These isometries imply that these correlation
functions should be conformal invariant. One of the shapes is produced by the
ordinary gravity action. The other shape is produced by a higher derivative
correction and could be as large as the gravity contribution. The parity
violating shape does not contribute to the bispectrum [1106.3228, 1108.0175],
even though it is present in the wavefunction. We also introduce a spinor
helicity formalism to describe de Sitter gravitational waves with circular
polarization. These results also apply to correlation functions in Anti-de
Sitter space. They also describe the general form of stress tensor correlation
functions, in momentum space, in a three dimensional conformal field theory.
Here all three shapes can arise, including the parity violating one.Comment: 51 pages, v2: Corrected statement about parity violation in the
gravitational wave bispectrum. Some other changes and references adde
The effect of a multi-component school-based social network intervention on children's body mass index:a four-arm intervention study
Objective: Schools are considered an important setting for stimulating healthy weight. The current study is unique in examining effects of a multi-component school-based social network intervention on children’s body mass index z-scores (zBMI).Methods: Four schools were randomly allocated to one of four conditions: a social network intervention using influence agents focusing on water consumption, physical activity, a combination of the two, or a passive control condition. Participants included a total of 201 6- to-11-year-old children (53.7% girls; Mage = 8.51, SDage = 0.93). At baseline, 149 (76.0%) participants had a healthy weight, 29 (14.8%) had overweight and 18 (9.2%) had obesity.Results: Linear mixed effect models indicated that a multi-component school-based social network intervention targeting both water consumption and physical activity was most effective in decreasing children’s zBMI.Conclusion: This study suggests that schools can contribute to the intervention of childhood obesity—even without involving the parents—by targeting both children’s water consumption and physical activity through influential peers, but more research is needed to identify mechanisms of change
Conformal weights in the Kerr/CFT correspondence
It has been conjectured that a near-extreme Kerr black hole is described by a
2d CFT. Previous work has shown that CFT operators dual to axisymmetric
gravitational perturbations have integer conformal weights. In this paper, we
study the analogous problem in 5d. We consider the most general near-extreme
vacuum black hole with two rotational symmetries. This includes Myers-Perry
black holes, black rings and Kaluza-Klein black holes. We find that operators
dual to gravitational (or electromagnetic or massless scalar field)
perturbations preserving both rotational symmetries have integer conformal
weights, the same for all black holes considered.Comment: 19 page
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
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