28,708 research outputs found
Some Issues in a Gauge Model of Unparticles
We address in a recent gauge model of unparticles the issues that are
important for consistency of a gauge theory, i.e., unitarity and Ward identity
of physical amplitudes. We find that non-integrable singularities arise in
physical quantities like cross section and decay rate from gauge interactions
of unparticles. We also show that Ward identity is violated due to the lack of
a dispersion relation for charged unparticles although the Ward-Takahashi
identity for general Green functions is incorporated in the model. A previous
observation that the unparticle's (with scaling dimension d) contribution to
the gauge boson self-energy is a factor (2-d) of the particle's has been
extended to the Green function of triple gauge bosons. This (2-d) rule may be
generally true for any point Green functions of gauge bosons. This implies that
the model would be trivial even as one that mimics certain dynamical effects on
gauge bosons in which unparticles serve as an interpolating field.Comment: v1:16 pages, 3 figures. v2: some clarifications made and presentation
improved, calculation and conclusion not modified; refs added and updated.
Version to appear in EPJ
Bounds on Unparticles from the Higgs Sector
We study supersymmetric QCD in the conformal window as a laboratory for
unparticle physics, and analyze couplings between the unparticle sector and the
Higgs sector. These couplings can lead to the unparticle sector being pushed
away from its scale invariant fixed point. We show that this implies that low
energy experiments will not be able to see unparticle physics, and the best
hope of seeing unparticles is in high energy collider experiments such as the
Tevatron and the LHC. We also demonstrate how the breaking of scale invariance
could be observed at these experiments.Comment: 9 pages, 3 figure
The Application of Predictor Feedback in Designing a Preview Controller for Discrete-Time Systems with Input Delay
© 2016 Fucheng Liao et al.This paper presents a method for designing a type one servomechanism for a discrete-time linear system with input delay subject to a previewable desired output and a nonmeasurable constant disturbance. The tracking problem of a delay system is transformed into a regulation problem of a delay-free system via constructing an augmented error system and a variable substitution. A controller is obtained with delay compensation and preview compensation based on preview control theory and the predictor method. When the state vector is not directly measurable, a full-dimensional observer is offered. The effectiveness of the design method is demonstrated by numerical simulations
From the chiral magnetic wave to the charge dependence of elliptic flow
The quark-gluon plasma formed in heavy ion collisions contains charged chiral
fermions evolving in an external magnetic field. At finite density of electric
charge or baryon number (resulting either from nuclear stopping or from
fluctuations), the triangle anomaly induces in the plasma the Chiral Magnetic
Wave (CMW). The CMW first induces a separation of the right and left chiral
charges along the magnetic field; the resulting dipolar axial charge density in
turn induces the oppositely directed vector charge currents leading to an
electric quadrupole moment of the quark-gluon plasma. Boosted by the strong
collective flow, the electric quadrupole moment translates into the charge
dependence of the elliptic flow coefficients, so that
(at positive net charge). Using the latest quantitative simulations of the
produced magnetic field and solving the CMW equation, we make further
quantitative estimates of the produced splitting and its centrality
dependence. We compare the results with the available experimental data.Comment: Contains 12 pages, 6 figures, written as a proceeding for the talk of
Y. Burnier at the conference "P and CP-odd Effects in Hot and Dense Matter
2012" held in BN
Metal-Insulator Transition of the LaAlO3-SrTiO3 Interface Electron System
We report on a metal-insulator transition in the LaAlO3-SrTiO3 interface
electron system, of which the carrier density is tuned by an electric gate
field. Below a critical carrier density n_c ranging from 0.5-1.5 * 10^13/cm^2,
LaAlO3-SrTiO3 interfaces, forming drain-source channels in field-effect devices
are non-ohmic. The differential resistance at zero channel bias diverges within
a 2% variation of the carrier density. Above n_c, the conductivity of the ohmic
channels has a metal-like temperature dependence, while below n_c conductivity
sets in only above a threshold electric field. For a given thickness of the
LaAlO3 layer, the conductivity follows a sigma_0 ~(n - n_c)/n_c characteristic.
The metal-insulator transition is found to be distinct from that of the
semiconductor 2D systems.Comment: 4 figure
Recommended from our members
Provision of secondary frequency regulation by coordinated dispatch of industrial loads and thermal power plants
Demand responsive industrial loads with high thermal inertia have potential to provide ancillary service for frequency regulation in the power market. To capture the benefit, this study proposes a new hierarchical framework to coordinate the demand responsive industrial loads with thermal power plants in an industrial park for secondary frequency control. In the proposed framework, demand responsive loads and generating resources are coordinated for optimal dispatch in two-time scales: (1) the regulation reserve of the industrial park is optimally scheduled in a day-ahead manner. The stochastic regulation signal is replaced by the specific extremely trajectories. Furthermore, the extremely trajectories are achieved by the day-ahead predicted regulation mileage. The resulting benefit is to transform the stochastic reserve scheduling problem into a deterministic optimization; (2) a model predictive control strategy is proposed to dispatch the industry park in real time with an objective to maximize the revenue. The proposed technology is tested using a real-world industrial electrolysis power system based upon Pennsylvania, Jersey, and Maryland (PJM) power market. Various scenarios are simulated to study the performance of the proposed approach to enable industry parks to provide ancillary service into the power market. The simulation results indicate that an industrial park with a capacity of 500 MW can provide up to 40 MW ancillary service for participation in the secondary frequency regulation. The proposed strategy is demonstrated to be capable of maintaining the economic and secure operation of the industrial park while satisfying performance requirements from the real world regulation market
Deep Learning for Single Image Super-Resolution: A Brief Review
Single image super-resolution (SISR) is a notoriously challenging ill-posed
problem, which aims to obtain a high-resolution (HR) output from one of its
low-resolution (LR) versions. To solve the SISR problem, recently powerful deep
learning algorithms have been employed and achieved the state-of-the-art
performance. In this survey, we review representative deep learning-based SISR
methods, and group them into two categories according to their major
contributions to two essential aspects of SISR: the exploration of efficient
neural network architectures for SISR, and the development of effective
optimization objectives for deep SISR learning. For each category, a baseline
is firstly established and several critical limitations of the baseline are
summarized. Then representative works on overcoming these limitations are
presented based on their original contents as well as our critical
understandings and analyses, and relevant comparisons are conducted from a
variety of perspectives. Finally we conclude this review with some vital
current challenges and future trends in SISR leveraging deep learning
algorithms.Comment: Accepted by IEEE Transactions on Multimedia (TMM
- …