18,493 research outputs found
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
Collisional energy loss above the critical temperature in QCD
We compute the collisional energy loss for a heavy quark above the critical
temperature in Quantum ChromoDynamics (QCD). We work in the semi Quark-Gluon
Plasma, which assumes that this region is dominated by the non-trivial holonomy
of the thermal Wilson line. Relative to the result to leading order in
perturbation theory, at a fixed value of the coupling constant we generically
we find that collisional energy loss is suppressed by powers of the Polyakov
loop, l < 1. For small values of the loop, this suppression is linear for the
scattering off of light quarks, and quadratic for the scattering off of gluons,
or for Compton scattering.Comment: 19 pages, 4 figure
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
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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
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