1,277 research outputs found
Causality of black holes in 4-dimensional Einstein-Gauss-Bonnet-Maxwell theory
We study charged black hole solutions in 4-dimensional (4D)
Einstein-Gauss-Bonnet-Maxwell theory to the linearized perturbation level. We
first compute the shear viscosity to entropy density ratio. We then demonstrate
how bulk causal structure analysis imposes a upper bound on the Gauss-Bonnet
coupling constant in the AdS space. Causality constrains the value of
Gauss-Bonnet coupling constant to be bounded by as .Comment: 13 pages, minor revision, references adde
Anisotropic plasma with a chemical potential and scheme-independent instabilities
Generically, the black brane solution with planar horizons is
thermodynamically stable. We find a counter-example to this statement by
demonstrating that an anisotropic black brane is unstable. We present a charged
black brane solution dual to a spatially anisotropic finite temperature
super Yang-Mills plasma at finite chemical potential.
This static and regular solution is obtained both numerically and analytically.
We uncover rich thermodynamic phase structures for this system by considering
the cases when the anisotropy constant "a" takes real and imaginary values,
respectively. In the case , the phase structure of this anisotropic
black brane is similar to that of Schwarzschild-AdS black hole with
horizon topology, yielding a thermodynamical instability at smaller horizon
radii. For the condition , the thermodynamics is dominated by the
black brane phase for all temperatures.Comment: 14pages,14figures, minor changes, PLB in pres
Variable bandwidth kernel regression estimation
In this paper we propose a variable bandwidth kernel regression estimator for
observations in to improve the classical
Nadaraya-Watson estimator. The bias is improved to the order of
under the condition that the fifth order derivative of the density function and
the sixth order derivative of the regression function are bounded and
continuous. We also establish the central limit theorems for the proposed ideal
and true variable kernel regression estimators. The simulation study confirms
our results and demonstrates the advantage of the variable bandwidth kernel
method over the classical kernel method.Comment: accepted by ESAIM: PS. 36 pages, 3 figure
Charged BTZ-like black hole solutions and the diffusivity-butterfly velocity relation
We show that there exists a class of charged BTZ-like black hole solutions in
Lifshitz spacetime with a hyperscaling violating factor. The charged BTZ is
characterized by a charge-dependent logarithmic term in the metric function. As
concrete examples, we give five such charged BTZ-like black hole solutions and
the standard charged BTZ metric can be regarded as a special instance of them.
In order to check the recent proposed universal relations between diffusivity
and the butterfly velocity, we first compute the diffusion constants of the
standard charged BTZ black holes and then extend our calculation to arbitrary
dimension , exponents and . Remarkably, the case and
is a very special in that the charge diffusion is a constant and
the energy diffusion might be ill-defined, but diverges. We
also compute the diffusion constants for the case that the DC conductivity is
finite but in the absence of momentum relaxation.Comment: 30 pages, 2 figure
A Non-linearity Correction Method for Fast Digital Multi-Channel Analyzers
AbstractFast digital multi-channel analyzers (FDMCA) which based on flash ADCs have been intensively used recently. The FDMCA is different from traditional MCAs which based on Wilkinson ADCs. The non-linearity, including the integral non-linearity (INL) and differential non-linearity (DNL), mainly arising from flash ADCs, degrade the accuracy of fast digital MCAs. To improve the non-linearity of FDMCA, a practical off-line correction method has been proposed in this paper. The non-linearity features of the FDMCA system is obtained by a special measurement previously. In light of that the non-linearity of a system is inherent; the non-linearity can be eliminated by comparing the data between the general measurement and the special one
Additional Listing Options on ebay: Are They Worth The Money
eBay is by far the world’s largest online auction site. Millions of people are doing transactions through it. eBay offers the sellers several additional listing options (“ALO” for short) at certain prices for them to enhance the visibility or attractiveness of their auction listings. In this paper we tried to find out how much these ALO can help to improve the outcome of an online auction, focusing mainly on the multiunit auctions of a certain brand of diet pill. The 116 data records were collected within a period of one month from the eBay’s “Diet and Weight loss” sub-category. In general, our idea can be applied to any other specific good sold on eBay. Our results provide important implications to eBay sellers in terms of deciding which ALO to use when listing his particular item for sale on eBay. Based on our findings, eBay or any auction sites could also apply our approach to estimate the optimal level of pricing of these ALO through computing the average value of the ALO for all transactions
The black hole to black hole phase transition probed by the D3-D7 model fermionic spectral functions
We consider the D3-D7 model and analyze the phase transition from the
black-hole phase to another black-hole phase using the spectral function of a
probe fermion on D7 in the presence of the finite density and temperature. From
the fermionic spectral functions, we study the temperature dependence of the
decay rate and we observe a jump in it at the critical temperature that
corresponds to the first order phase transition. We found that if we assume
that the Drude model works in this case so that the resistivity is proportional
to the fermion decay rate, the jump matches the resistivity data in a heavy
fermion material.Comment: 21 pages, 6 figure
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