37,166 research outputs found
First-order and continuous quantum phase transitions in the anisotropic quantum Rabi-Stark model
Various quantum phase transitions in the anisotropic Rabi-Stark model with
both the nonlinear Stark coupling and the linear dipole coupling between a
two-level system and a single-mode cavity are studied in this work. The
first-order quantum phase transitions are detected by the level crossing of the
ground-state and the first-excited state with the help of the pole structure of
the transcendental functions derived by the Bogoliubov operators approach. As
the nonlinear Stark coupling is the same as the cavity frequency, this model
can be solved by mapping to an effective quantum oscillator. All energy levels
close at the critical coupling in this case, indicating continuous quantum
phase transitions. The critical gap exponent is independent of the anisotropy
as long as the counter-rotating wave coupling is present, but essentially
changed if the counter-rotating wave coupling disappears completely. It is
suggested that the gapless Goldstone mode excitations could appear above a
critical coupling in the present model in the rotating-wave approximation.Comment: 9 pages, 4 figure
The Weighted Sum Rate Maximization in MIMO Interference Networks: The Minimax Lagrangian Duality and Algorithm
We take a new perspective on the weighted sum-rate maximization in
multiple-input multiple-output (MIMO) interference networks, by formulating an
equivalent max-min problem. This seemingly trivial reformulation has
significant implications: the Lagrangian duality of the equivalent max-min
problem provides an elegant way to establish the sum-rate duality between an
interference network and its reciprocal when such a duality exists, and more
importantly, suggests a novel iterative minimax algorithm for the weighted
sum-rate maximization. Moreover, the design and convergence proof of the
algorithm use only general convex analysis. They apply and extend to any
max-min problems with similar structure, and thus provide a general class of
algorithms for such optimization problems. This paper presents a promising step
and lends hope for establishing a general framework based on the minimax
Lagrangian duality for characterizing the weighted sum-rate and developing
efficient algorithms for general MIMO interference networks.Comment: 10 pages, 6 figures, submitted for publicatio
Early Fire Detection Using HEP and Space-time Analysis
In this article, a video base early fire alarm system is developed by
monitoring the smoke in the scene. There are two major contributions in this
work. First, to find the best texture feature for smoke detection, a general
framework, named Histograms of Equivalent Patterns (HEP), is adopted to achieve
an extensive evaluation of various kinds of texture features. Second, the
\emph{Block based Inter-Frame Difference} (BIFD) and a improved version of
LBP-TOP are proposed and ensembled to describe the space-time characteristics
of the smoke. In order to reduce the false alarms, the Smoke History Image
(SHI) is utilized to register the recent classification results of candidate
smoke blocks. Experimental results using SVM show that the proposed method can
achieve better accuracy and less false alarm compared with the state-of-the-art
technologies.Comment: 9 pages, 13 figure
Quantum Theory for Mesoscopic Electric Circuits and Its Applications
This talk is assumed to exhibit an overview of the quantum theory for
mesoscopic electric circuits and some of its further developments. In the
theory the importance of the discreteness of electronic charge in mesoscopic
electric circuit is addressed. The mesoscopic LC-design is quantized in accord
with the charge discreteness. The uncertainty relation for electric charge and
current is given. Because the stationary Schr\"odinger equation is turned to be
Mathieu equation in -representation, the wave function and energy spectrum
is formally solved. As further applications, the persistent current is obtained
by considering the mesoscopic ring as a pure L-design. The Coulomb blockade
phenomenon occurs when applying the theory to the pure C-design. Concerning the
time evolution of the states for mesoscopic electric circuit, we are able to
study it by the method of characteristics. In order to study the dissipative
effect in the circuit, we use density-matrix formulation. In this formulation,
several type of ``off diagonal'' dissipations are expected to be discussed.Comment: Latex, 6 pages of two-collumn style, 0 figur
Asymptotics of signed Bernoulli convolutions scaled by multinacci numbers
We study the signed Bernoulli convolution
where satisfies for some
integer . When is odd, we show that the variation
coincides the unsigned Bernoulli convolution
When is
even, we obtain the exact asymptotic of the total variation
as .Comment: 15 page
Persistent Spread Measurement for Big Network Data Based on Register Intersection
Persistent spread measurement is to count the number of distinct elements
that persist in each network flow for predefined time periods. It has many
practical applications, including detecting long-term stealthy network
activities in the background of normal-user activities, such as stealthy DDoS
attack, stealthy network scan, or faked network trend, which cannot be detected
by traditional flow cardinality measurement. With big network data, one
challenge is to measure the persistent spreads of a massive number of flows
without incurring too much memory overhead as such measurement may be performed
at the line speed by network processors with fast but small on-chip memory. We
propose a highly compact Virtual Intersection HyperLogLog (VI-HLL) architecture
for this purpose. It achieves far better memory efficiency than the best prior
work of V-Bitmap, and in the meantime drastically extends the measurement
range. Theoretical analysis and extensive experiments demonstrate that VI-HLL
provides good measurement accuracy even in very tight memory space of less than
1 bit per flow.Comment: ACM SIGMETRICS 201
Acoustic scattering by a cylinder near a pressure release surface
This paper presents a study of acoustic scattering by a cylinder of either
infinite or finite length near a flat pressure-release surface. A novel
self-consistent method is developed to describe the multiple scattering
interactions between the cylinder and the surface. The complete scattering
amplitude for the cylinder is derived from a set of equations, and is
numerically evaluated. The results show that the presence of the surface can
either enhance or reduce the scattering of the cylinder, depending on the
frequency, the composition of the cylinder, and the distance between the
cylinder and the surface. Both air-filled and rigid cylinders are considered.Comment: 8 figure
The Twin Conjugacy Search Problem and Applications
We propose a new computational problem over the noncommutative group, called
the twin conjugacy search problem. This problem is related to the conjugacy
search problem and can be used for almost all of the same cryptographic
constructions that are based on the conjugacy search problem. However, our new
problem is at least hard as the conjugacy search problem. Moreover, the twin
conjugacy search problem have many applications. One of the most important
applications, we propose a trapdoor test which can replace the function of the
decision oracle. We also show other applications of the problem, including: a
non-interactive key exchange protocol and a key exchange protocol, a new
encryption scheme which is secure against chosen ciphertext attack, with a very
simple and tight security proof and short ciphertexts, under a weak assumption,
in the random oracle model
Analytical solutions by squeezing to the anisotropic Rabi model in the nonperturbative deep-strong coupling regime
A novel, unexplored nonperturbative deep-strong coupling (npDSC) achieved in
superconducting circuits has been studied in the anisotropic Rabi model by the
generalized squeezing rotating-wave approximation (GSRWA). Energy levels are
evaluated analytically from the reformulated Hamiltonian and agree well with
numerical ones under a wide range of coupling strength. Such improvement
ascribes to deformation effects in the displaced-squeezed state presented by
the squeezed momentum variance, which are omitted in the previous displaced
state. The population dynamics confirm the validity of our approach for the
npDSC strength. Our approach paves a way to the exploration of analysis in
qubit-oscillator experiments for the npDSC strength by the displaced-squeezed
state.Comment: 8 pages,4 figure
A characterization of arithmetic functions satisfying
In this paper, we mainly discuss the characterization of a class of
arithmetic functions such that
. We obtain a
characterization with given condition, propose a conjecture and show the result
holds for
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