Periodic solitons for the elliptic-elliptic focussing Davey-Stewartson equations

We consider the elliptic-elliptic, focussing Davey-Stewartson equations, which have an explicit bright line soliton solution. The existence of a family of periodic solitons, which have the profile of the line soliton in the longitudinal spatial direction and are periodic in the transverse spatial direction, is established using dynamical systems arguments. We also show that the line soliton is linearly unstable with respect to perturbations in the transverse direction.Comment: arXiv admin note: text overlap with arXiv:1411.247

Bose-Einstein condensation in linear sigma model at Hartree and large N approximation

The BEC of charged pions is investigated in the framework of O(4) linear sigma model. By using Cornwall-Jackiw-Tomboulis formalism, we have derived the gap equations for the effective masses of the mesons at finite temperature and finite isospin density. The BEC is discussed in chiral limit and non-chiral limit at Hartree approximation and also at large N approximation.Comment: 11 pages, 9 figure

Non-fragile H∞ control with randomly occurring gain variations, distributed delays and channel fadings

This study is concerned with the non-fragile H∞ control problem for a class of discrete-time systems subject to randomly occurring gain variations (ROGVs), channel fadings and infinite-distributed delays. A new stochastic phenomenon (ROGVs), which is governed by a sequence of random variables with a certain probabilistic distribution, is put forward to better reflect the reality of the randomly occurring fluctuation of controller gains implemented in networked environments. A modified stochastic Rice fading model is then exploited to account for both channel fadings and random time-delays in a unified representation. The channel coefficients are a set of mutually independent random variables which abide by any (not necessarily Gaussian) probability density function on [0, 1]. Attention is focused on the analysis and design of a non-fragile H∞ outputfeedback controller such that the closed-loop control system is stochastically stable with a prescribed H∞ performance. Through intensive stochastic analysis, sufficient conditions are established for the desired stochastic stability and H∞ disturbance attenuation, and the addressed non-fragile control problem is then recast as a convex optimisation problem solvable via the semidefinite programme method. An example is finally provided to demonstrate the effectiveness of the proposed design method

On the direct shock wave problem. a modified theory /final report on bodies with spherical nose/

Modification of mathematical approach to general body problem for investigating direct shock wave problem for bodies with spherical nos

H∞ fault estimation with randomly occurring uncertainties, quantization effects and successive packet dropouts: The finite-horizon case

In this paper, the finite-horizon H∞ fault estimation problem is investigated for a class of uncertain nonlinear time-varying systems subject to multiple stochastic delays. The randomly occurring uncertainties (ROUs) enter into the system due to the random fluctuations of network conditions. The measured output is quantized by a logarithmic quantizer before being transmitted to the fault estimator. Also, successive packet dropouts (SPDs) happen when the quantized signals are transmitted through an unreliable network medium. Three mutually independent sets of Bernoulli-distributed white sequences are introduced to govern the multiple stochastic delays, ROUs and SPDs. By employing the stochastic analysis approach, some sufficient conditions are established for the desired finite-horizon fault estimator to achieve the specified H∞ performance. The time-varying parameters of the fault estimator are obtained by solving a set of recursive linear matrix inequalities. Finally, an illustrative numerical example is provided to show the effectiveness of the proposed fault estimation approach

A Revisit to Top Quark Forward-Backward Asymmetry

We analyze various models for the top quark forward-backward asymmetry ($A^t_{FB}$) at the Tevatron, using the latest CDF measurements on different $A^t_{FB}$s and the total cross section. The axigluon model in Ref. \cite{paul} has difficulties in explaining the large rapidity dependent asymmetry and mass dependent asymmetry simultaneously and the parameter space relevant to $A^t_{FB}$ is ruled out by the latest dijet search at ATLAS. In contrast to Ref. \cite{cp}, we demonstrate that the large parameter space in this model with a $U(1)_d$ flavor symemtry is not ruled out by flavor physics. The $t$-channel flavor-violating $Z^{\prime}$ \cite{hitoshi}, $W^{\prime}$\cite{waiyee} and diquark \cite{tim} models all have parameter regions that satisfy different $A_{FB}$ measurements within 1 $\sigma$. However, the heavy $Z^{\prime}$ model which can be marginally consistent with the total cross section is severely constrained by the Tevatron direct search of same-sign top quark pair. The diquark model suffers from too large total cross section and is difficult to fit the $t \bar{t}$ invariant mass distribution. The electroweak precision constraints on the $W'$ model based on $Z'$-$Z$ mixings is estimated and the result is rather weak ($m_{Z'} > 450$ GeV). Therefore, the heavy $W^{\prime}$ model seems to give the best fit for all the measurements. The $W^{\prime}$ model predicts the $t\bar{t}+j$ signal from $tW^{\prime}$ production and is 10%-50% of SM $t\bar{t}$ at the 7 TeV LHC. Such $t+j$ resonance can serve as the direct test of the $W^{\prime}$ model.Comment: 25 pages, 7 figures, 1 tabl