46,934 research outputs found
Vanishing theorems on complete Riemannian manifold with a parallel -form
In this article, we first consider the \textit{Morse-Novikov
cohomology} on a complete Riemannian manifold equipped with a parallel
-form which includes Vaisman manifold. Based on a vanishing theorem of
\textit{Morse-Novikov cohomology}, we prove that the -harmonic
forms on are identically zero.Comment: 13 pages; to appear in Mathematische Nachrichte
Phase-isometries on real normed spaces
We say that a mapping between two real normed spaces is
a phase-isometry if it satisfies the functional equation \begin{eqnarray*}
\{\|f(x)+f(y)\|, \|f(x)-f(y)\|\}=\{\|x+y\|, \|x-y\|\} \quad (x,y\in
X).\end{eqnarray*} A generalized Mazur-Ulam question is whether every
surjective phase-isometry is a multiplication of a linear isometry and a map
with range . This assertion is also an extension of a fundamental
statement in the mathematical description of quantum mechanics, Wigner's
theorem to real normed spaces. In this paper, we show that for every space
the problem is solved in positive way if is a smooth normed space, an
-type space or an -space with
being an index set.Comment: 16page
Analytical approach on linear and nonlinear pulse propagations in an open Lambda-type molecular system with Doppler broadening
We develop a systematic analytical approach on linear and nonlinear pulse
propagations in an open Lambda-type molecular system with Doppler broadening.
In linear case, by using residue theorem and a spectrum decomposition method,
we prove that there exists a crossover from electromagnetically induced
transparency (EIT) to Autler-Townes splitting (ATS) for co-propagating
configuration of probe and control fields. However, there is no EIT and hence
no EIT-ATS crossover for counter-propagating configuration. We give various
explicit formulas, including probe-field spectrum decomposition, EIT condition,
width of EIT transparency window, as well as a comparison with the result of
cold molecules. Our analytical result agrees well with the experimental one
reported recently by A. Lazoudis et al. [Phys. Rev.A82, 023812 (2010)]. In
nonlinear case, by using the method of multiple-scales, we derive a nonlinear
envelope equation for probe-field propagation. We show that stable ultraslow
solitons can be realized in the open molecular system.Comment: 20 pages, 9 figure
Adaptive Power System Emergency Control using Deep Reinforcement Learning
Power system emergency control is generally regarded as the last safety net
for grid security and resiliency. Existing emergency control schemes are
usually designed off-line based on either the conceived "worst" case scenario
or a few typical operation scenarios. These schemes are facing significant
adaptiveness and robustness issues as increasing uncertainties and variations
occur in modern electrical grids. To address these challenges, for the first
time, this paper developed novel adaptive emergency control schemes using deep
reinforcement learning (DRL), by leveraging the high-dimensional feature
extraction and non-linear generalization capabilities of DRL for complex power
systems. Furthermore, an open-source platform named RLGC has been designed for
the first time to assist the development and benchmarking of DRL algorithms for
power system control. Details of the platform and DRL-based emergency control
schemes for generator dynamic braking and under-voltage load shedding are
presented. Extensive case studies performed in both two-area four-machine
system and IEEE 39-Bus system have demonstrated the excellent performance and
robustness of the proposed schemes.Comment: 12 page
Translation-Invariant Representation for Cumulative Foot Pressure Images
Human can be distinguished by different limb movements and unique ground
reaction force. Cumulative foot pressure image is a 2-D cumulative ground
reaction force during one gait cycle. Although it contains pressure spatial
distribution information and pressure temporal distribution information, it
suffers from several problems including different shoes and noise, when putting
it into practice as a new biometric for pedestrian identification. In this
paper, we propose a hierarchical translation-invariant representation for
cumulative foot pressure images, inspired by the success of Convolutional deep
belief network for digital classification. Key contribution in our approach is
discriminative hierarchical sparse coding scheme which helps to learn useful
discriminative high-level visual features. Based on the feature representation
of cumulative foot pressure images, we develop a pedestrian recognition system
which is invariant to three different shoes and slight local shape change.
Experiments are conducted on a proposed open dataset that contains more than
2800 cumulative foot pressure images from 118 subjects. Evaluations suggest the
effectiveness of the proposed method and the potential of cumulative foot
pressure images as a biometric.Comment: 6 page
Generalized-Lush Spaces and the Mazur-Ulam Property
We introduce a new class of Banach spaces, called generalized-lush spaces
(GL-spaces for short), which contains almost-CL-spaces, separable lush spaces
(specially, separable -rich subspaces of ), and even the
two-dimensional space with hexagonal norm. We obtain that the space of
the vector-valued continuous functions is a GL-space whenever is, and show
that the GL-space is stable under -, - and -sums. As an
application, we prove that the Mazur-Ulam property holds for a larger class of
Banach spaces, called local-GL-spaces, including all lush spaces and GL-spaces.
Furthermore, we generalize the stability properties of GL-spaces to
local-GL-spaces. From this, we can obtain many examples of Banach spaces having
the Mazur-Ulam property.Comment: 16 page
Lossless Airy Surface Polaritons in a Metamaterial via Active Raman Gain
We propose a scheme to realize a lossless propagation of linear and nonlinear
Airy surface polaritons (SPs) via active Raman gain (ARG). The system we
suggest is a planar interface superposed by a negative index metamaterial
(NIMM) and a dielectric, where three-level quantum emitters are doped. By using
the ARG from the quantum emitters and the destructive interference effect
between the electric and magnetic responses from the NIMM, we show that not
only the Ohmic loss of the NIMM but also the light absorption of the quantum
emitters can be completely eliminated. As a result, non-diffractive Airy SPs
may propagate for very long distance without attenuation. We also show that the
Kerr nonlinearity of the system can be largely enhanced due to the introduction
of the quantum emitters and hence lossless Airy surface polaritonic solitons
with very low power can be generated in the system
Global existence and large time behavior for the system of compressible adiabatic flow through porous media in
The system of compressible adiabatic flow through porous media is considered
in in the present paper. The global existence and uniqueness
of classical solutions are obtained when the initial data is near its
equilibrium. We also show that the pressure of the system converges to its
equilibrium state at the same -rate as the Navier-Stokes
equations without heat conductivity, but the velocity of the system decays at
the -rate , which is faster than the -rate
for the Navier-Stokes equations without heat conductivity [3]
Crossover from Electromagnetically Induced Transparency to Autler-Townes Splitting in Open V-Type Molecular Systems
We investigate electromagnetically induced transparency (EIT) and
Autler-Townes splitting(ATS) in an open V-type molecular system. Through
detailed analytical calculations on the absorption spectrum of probe laser
field by using residue theorem and spectrum decomposition, we find that EIT may
occur and there exists a crossover from EIT to ATS (i.e. EIT-ATS crossover) for
hot molecules. However, there is no EIT and hence no EIT-ATS crossover for cold
molecules. Furthermore, we prove that for hot molecules EIT is allowed even for
a counter-propagating configuration. We provide explicit formulas of EIT
conditions and widths of EIT transparency windows of probe field when hot
molecules work in co-propagating and counter-propagating configurations,
respectively. Our theoretical result agrees well with the recent experimental
one reported by Lazoudis et al. [Phys. Rev. A 83, 063419 (2011)].Comment: 26 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1212.565
Theoretical analysis on quantum interference effect in fast-light media
We make a systematic theoretical analysis on the quantum interference (QI)
effects in various fast-light media (including gain-assisted , gain-assisted
ladder-I, and gain-assisted ladder-II atomic systems). We show that such
fast-light media are capable of not only completely eliminating the absorption
but also suppressing the gain of signal field, and hence provide the
possibility to realize a stable propagation of the signal field with a
superluminal velocity. We find that there is a destructive (constructive) QI
effect in gain-assisted ladder-I (gain-assisted N) system, but no QI in the
gain-assisted ladder-II system; furthermore, a crossover from destructive
(constructive) QI to Autler-Townes splitting may occur for the gain-assisted
ladder-I (gain-assisted N) system when the control field of the system is
modulated. Our theoretical analysis can be applied to other multi-level
systems, and the results obtained may have promising applications in optical
and quantum information processing and transmission
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