2,731 research outputs found
Ads(3)/CFT(2) to Ads(2)/CFT(1)
It has been suggested that the quantum generalization of the Wald entropy for
an extremal black hole is the logarithm of the ground state degeneracy of a
dual quantum mechanics in a fixed charge sector. We test this proposal for
supersymmetric extremal BTZ black holes for which there is an independent
definition of the quantum entropy as the logarithm of the degeneracy of
appropriate states in the dual 1+1 dimensional superconformal field theory. We
find that the two proposals agree. This analysis also suggests a possible route
to deriving the OSV conjecture.Comment: LaTeX file, 14 pages; v2: references added; v3: comments and
refernces added; v4: expanded discussion on the role of cut-of
On the universal hydrodynamics of strongly coupled CFTs with gravity duals
It is known that the solutions of pure classical 5D gravity with
asymptotics can describe strongly coupled large N dynamics in a universal
sector of 4D conformal gauge theories. We show that when the boundary metric is
flat we can uniquely specify the solution by the boundary stress tensor. We
also show that in the Fefferman-Graham coordinates all these solutions have an
integer Taylor series expansion in the radial coordinate (i.e. no terms).
Specifying an arbitrary stress tensor can lead to two types of pathologies, it
can either destroy the asymptotic AdS boundary condition or it can produce
naked singularities. We show that when solutions have no net angular momentum,
all hydrodynamic stress tensors preserve the asymptotic AdS boundary condition,
though they may produce naked singularities. We construct solutions
corresponding to arbitrary hydrodynamic stress tensors in Fefferman-Graham
coordinates using a derivative expansion. In contrast to Eddington-Finkelstein
coordinates here the constraint equations simplify and at each order it is
manifestly Lorentz covariant. The regularity analysis, becomes more elaborate,
but we can show that there is a unique hydrodynamic stress tensor which gives
us solutions free of naked singularities. In the process we write down explicit
first order solutions in both Fefferman-Graham and Eddington-Finkelstein
coordinates for hydrodynamic stress tensors with arbitrary . Our
solutions can describe arbitrary (slowly varying) velocity configurations. We
point out some field-theoretic implications of our general results.Comment: 39 pages, two appendices added, in appendix A the proof of the power
series solution has been detailed, in appendix B, we have commented on method
of fixing by calculating curvature invariant
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Behavioral modeling of DRACO : a peripheral interface ASIC
This paper describes the behavioral modeling of DRACO, a peripheral interface Application Specific Integrated Circuit (ASIC) developed by Rockwell International for numerical control applications. The behavioral model was generated from a data sheet of the fabricated chip, which primarily described the chip's input-output functionality, physical and operational characteristics, and a functional block diagram. The data sheet contained very little abstract behavioral information. This report describes the abstract behavioral model of the DRACO chip, and uses flowcharts and VHDL to capture the behavior. The behavioral model was developed through reverse engineering of the data sheet description, supplemented by further consultation with designers of the DRACO ASIC at Rockwell Intemational. The report describes typical behavioral test sequences that were applied to the DRACO VHDL model to verify its correctness. The appendices contain the original DRACO datasheet and the VHDL code used to capture DRACO's behavior
Scaling Configuration of Energy Harvesting Sensors with Reinforcement Learning
With the advent of the Internet of Things (IoT), an increasing number of
energy harvesting methods are being used to supplement or supplant battery
based sensors. Energy harvesting sensors need to be configured according to the
application, hardware, and environmental conditions to maximize their
usefulness. As of today, the configuration of sensors is either manual or
heuristics based, requiring valuable domain expertise. Reinforcement learning
(RL) is a promising approach to automate configuration and efficiently scale
IoT deployments, but it is not yet adopted in practice. We propose solutions to
bridge this gap: reduce the training phase of RL so that nodes are operational
within a short time after deployment and reduce the computational requirements
to scale to large deployments. We focus on configuration of the sampling rate
of indoor solar panel based energy harvesting sensors. We created a simulator
based on 3 months of data collected from 5 sensor nodes subject to different
lighting conditions. Our simulation results show that RL can effectively learn
energy availability patterns and configure the sampling rate of the sensor
nodes to maximize the sensing data while ensuring that energy storage is not
depleted. The nodes can be operational within the first day by using our
methods. We show that it is possible to reduce the number of RL policies by
using a single policy for nodes that share similar lighting conditions.Comment: 7 pages, 5 figure
Heat Kernels on the AdS(2) cone and Logarithmic Corrections to Extremal Black Hole Entropy
We develop new techniques to efficiently evaluate heat kernel coefficients
for the Laplacian in the short-time expansion on spheres and hyperboloids with
conical singularities. We then apply these techniques to explicitly compute the
logarithmic contribution to black hole entropy from an N=4 vector multiplet
about a Z(N) orbifold of the near-horizon geometry of quarter--BPS black holes
in N=4 supergravity. We find that this vanishes, matching perfectly with the
prediction from the microstate counting. We also discuss possible
generalisations of our heat kernel results to higher-spin fields over Z(N)
orbifolds of higher-dimensional spheres and hyperboloids.Comment: 41 page
Logarithmic Corrections to Extremal Black Hole Entropy in N = 2, 4 and 8 Supergravity
We compute the logarithmic correction to black hole entropy about
exponentially suppressed saddle points of the Quantum Entropy Function
corresponding to Z(N) orbifolds of the near horizon geometry of the extremal
black hole under study. By carefully accounting for zero mode contributions we
show that the logarithmic contributions for quarter--BPS black holes in N=4
supergravity and one--eighth BPS black holes in N=8 supergravity perfectly
match with the prediction from the microstate counting. We also find that the
logarithmic contribution for half--BPS black holes in N = 2 supergravity
depends non-trivially on the Z(N) orbifold. Our analysis draws heavily on the
results we had previously obtained for heat kernel coefficients on Z(N)
orbifolds of spheres and hyperboloids in arXiv:1311.6286 and we also propose a
generalization of the Plancherel formula to Z(N) orbifolds of hyperboloids to
an expression involving the Harish-Chandra character of SL(2,R), a result which
is of possible mathematical interest.Comment: 40 page
Supersymmetric Localization for BPS Black Hole Entropy: 1-loop Partition Function from Vector Multiplets
We use the techniques of supersymmetric localization to compute the BPS black
hole entropy in N=2 supergravity. We focus on the n_v+1 vector multiplets on
the black hole near horizon background which is AdS_2 x S^2 space. We find the
localizing saddle point of the vector multiplets by solving the localization
equations, and compute the exact one loop partition function on the saddle
point. Furthermore, we propose the appropriate functional integration measure.
Through this measure, the one loop determinant is written in terms of the
radius of the physical metric, which depends on the localizing saddle point
value of the vector multiplets. The result for the one loop determinant is
consistent with the logarithmic corrections to the BPS black hole entropy from
vector multiplets.Comment: 28+16 pages, improved discussion on the boundary mode in the 4.2 and
conclusion sectio
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