4,602 research outputs found
Dynamics of Gravity as Thermodynamics on the Spherical Holographic Screen
The dynamics of general Lovelock gravity, viewed on an arbitrary spherically
symmetric surface as a holographic screen, is recast as the form of some
generalized first law of thermodynamics on the screen. From this observation
together with other two distinct aspects, where exactly the same temperature
and entropy on the screen arise, it is argued that the thermodynamic
interpretation of gravity is physically meaningful not only on the horizon, but
also on a general spherically symmetric screen.Comment: 10 pages, revtex4; v2: minor corrections, references added? v3: the
summary paragraph replaced by the discussion of the general static case,
minor corrections/clarifications/modifications, references added, match the
published versio
Bulk Viscosity of dual Fluid at Finite Cutoff Surface via Gravity/Fluid correspondence in Einstein-Maxwell Gravity
Based on the previous paper arXiv:1207.5309, we investigate the possibility
to find out the bulk viscosity of dual fluid at the finite cutoff surface via
gravity/fluid correspondence in Einstein-Maxwell gravity. We find that if we
adopt new conditions to fix the undetermined parameters contained in the stress
tensor and charged current of the dual fluid, two new terms appear in the
stress tensor of the dual fluid. One new term is related to the bulk viscosity
term, while the other can be related to the perturbation of energy density. In
addition, since the parameters contained in the charged current are the same,
the charged current is not changed.Comment: 15 pages, no figure, typos corrected, new references and comments
added, version accepted by PL
From Petrov-Einstein-Dilaton-Axion to Navier-Stokes equation in anisotropic model
In this paper we generalize the previous works to the case that the
near-horizon dynamics of the Einstein-Dilaton-Axion theory can be governed by
the incompressible Navier-Stokes equation via imposing the Petrov-like boundary
condition on hypersurfaces in the non-relativistic and near-horizon limit. The
dynamical shear viscosity of such dual horizon fluid in our scenario,
which isotropically saturates the Kovtun-Son-Starinet (KSS) bound, is
independent of both the dilaton field and axion field in that limit.Comment: 13 pages,no figures; v2: 15 page, Equation.(33), some discussions and
references added, minor corrections , Version accepted for publication in
Physics Letters
Extremal Isolated Horizon/CFT Correspondence
The near-horizon limit of the extremal (weakly) isolated horizon is obtained
under the Bondi-like coordinates. For the vacuum case, explicit coordinate
transformation relating the near-horizon metric under the Bondi-like
coordinates and the standard Poincar\'e-type or global near-horizon metric of
the extremal Kerr black hole is found, which shows that the two geometries are
the same. Combined with the known thermodynamics of the (weakly) isolated
horizon, it is argued that the Kerr/CFT correspondence can be generalized to
the case of a large class of non-stationary extremal black holes.Comment: 13 pages, no figure, revtex4; v2: abstract revised, minor
corrections, references added; v3: minor corrections, version to appear in
PR
A New Two-Dimensional Functional Material with Desirable Bandgap and Ultrahigh Carrier Mobility
Two-dimensional (2D) semiconductors with direct and modest bandgap and
ultrahigh carrier mobility are highly desired functional materials for
nanoelectronic applications. Herein, we predict that monolayer CaP3 is a new 2D
functional material that possesses not only a direct bandgap of 1.15 eV (based
on HSE06 computation), and also a very high electron mobility up to 19930 cm2
V-1 s-1, comparable to that of monolayer phosphorene. More remarkably, contrary
to the bilayer phosphorene which possesses dramatically reduced carrier
mobility compared to its monolayer counterpart, CaP3 bilayer possesses even
higher electron mobility (22380 cm2 V-1 s-1) than its monolayer counterpart.
The bandgap of 2D CaP3 can be tuned over a wide range from 1.15 to 0.37 eV
(HSE06 values) through controlling the number of stacked CaP3 layers. Besides
novel electronic properties, 2D CaP3 also exhibits optical absorption over the
entire visible-light range. The combined novel electronic, charge mobility, and
optical properties render 2D CaP3 an exciting functional material for future
nanoelectronic and optoelectronic applications
A Two-Phase Maximum-Likelihood Sequence Estimation for Receivers with Partial CSI
The optimality of the conventional maximum likelihood sequence estimation
(MLSE), also known as the Viterbi Algorithm (VA), relies on the assumption that
the receiver has perfect knowledge of the channel coefficients or channel state
information (CSI). However, in practical situations that fail the assumption,
the MLSE method becomes suboptimal and then exhaustive checking is the only way
to obtain the ML sequence. At this background, considering directly the ML
criterion for partial CSI, we propose a two-phase low-complexity MLSE
algorithm, in which the first phase performs the conventional MLSE algorithm in
order to retain necessary information for the backward VA performed in the
second phase. Simulations show that when the training sequence is moderately
long in comparison with the entire data block such as 1/3 of the block, the
proposed two-phase MLSE can approach the performance of the optimal exhaustive
checking. In a normal case, where the training sequence consumes only 0.14 of
the bandwidth, our proposed method still outperforms evidently the conventional
MLSE.Comment: 5 pages and 4 figure
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