80,189 research outputs found
Thermodynamic properties of a simple, confining model
We study the equilibrium thermodynamics of a simple, confining, DSE-model of
2-flavour QCD at finite temperature and chemical potential. The model has two
phases: one characterised by confinement and dynamical chiral symmetry
breaking; and the other by their absence. The phase boundary is defined by the
zero of the vacuum-pressure difference between the confined and deconfined
phases. Chiral symmetry restoration and deconfinement are coincident with the
transition being of first order, except for , where it is second order.
Nonperturbative modifications of the dressed-quark propagator persist into the
deconfined domain and lead to a dispersion law modified by a
dynamically-generated, momentum-dependent mass-scale. This entails that the
Stefan-Boltzmann limit for the bulk thermodynamic quantities is attained only
for large values of temperature and chemical potential.Comment: 11 pages, LaTeX, epsfig.sty, elsart.st
Temperature, chemical potential and the rho meson
We describe some applications of the Dyson-Schwinger equations at
nonzero-(T,mu). Employing a simple model dressed-gluon propagator we determine
the boundary of the deconfinement phase transition and the medium dependence of
rho-meson properties. We introduce an extension to describe the time-evolution
of scalar and vector self energies.Comment: 6 pages, LaTeX with 3 EPS figures; Contribution to the 'International
Workshop XXVIII on Gross Properties of Nuclei and Nuclear Excitations',
Hirschegg, Austria, 16-22.01.200
Optimal cooperative control synthesis of active displays
A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/s(2) plant, and then to an F-15 type aircraft in a multi-channel task. Utilizing the closed loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts
A generalized spatiotemporal covariance model for stationary background in analysis of MEG data
Using a noise covariance model based on a single Kronecker product of spatial
and temporal covariance in the spatiotemporal analysis of MEG data was
demonstrated to provide improvement in the results over that of the commonly
used diagonal noise covariance model. In this paper we present a model that is
a generalization of all of the above models. It describes models based on a
single Kronecker product of spatial and temporal covariance as well as more
complicated multi-pair models together with any intermediate form expressed as
a sum of Kronecker products of spatial component matrices of reduced rank and
their corresponding temporal covariance matrices. The model provides a
framework for controlling the tradeoff between the described complexity of the
background and computational demand for the analysis using this model. Ways to
estimate the value of the parameter controlling this tradeoff are also
discussedComment: 4 pages, EMBS 2006 conferenc
Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 1: Analysis methods
As aircraft become larger and lighter due to design requirements for increased payload and improved fuel efficiency, they will also become more flexible. For highly flexible vehicles, the handling qualities may not be accurately predicted by conventional methods. This study applies two analysis methods to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop model analysis technique. This method considers the effects of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Volume 1 consists of the development and application of the two analysis methods described above
Quantum effects with an X-ray free electron laser
A quantum kinetic equation coupled with Maxwell's equation is used to
estimate the laser power required at an XFEL facility to expose intrinsically
quantum effects in the process of QED vacuum decay via spontaneous pair
production. A 9 TW-peak XFEL laser with photon energy 8.3 keV could be
sufficient to initiate particle accumulation and the consequent formation of a
plasma of spontaneously produced pairs. The evolution of the particle number in
the plasma will exhibit non-Markovian aspects of the strong-field pair
production process and the plasma's internal currents will generate an electric
field whose interference with that of the laser leads to plasma oscillations.Comment: 4 pages, LaTeX2
DSE Hadron Phenomenology
A perspective on the contemporary use of Dyson-Schwinger equations, focusing
on some recent phenomenological applications: a description and unification of
light-meson observables using a one-parameter model of the effective
quark-quark interaction, and studies of leptonic and nonleptonic nucleon form
factors.Comment: 7 pages, sprocl.sty, epsfig.sty. Contribution to the Proceedings of
the Workshop on Light-Cone QCD and Nonperturbative Hadron Physics, Adelaide,
Australia, 13-22 Dec 199
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