29,717 research outputs found
Estimation of the shear viscosity at finite net-baryon density from A+A collision data at GeV
Hybrid approaches based on relativistic hydrodynamics and transport theory
have been successfully applied for many years for the dynamical description of
heavy ion collisions at ultrarelativistic energies. In this work a new viscous
hybrid model employing the hadron transport approach UrQMD for the early and
late non-equilibrium stages of the reaction, and 3+1 dimensional viscous
hydrodynamics for the hot and dense quark-gluon plasma stage is introduced.
This approach includes the equation of motion for finite baryon number, and
employs an equation of state with finite net-baryon density to allow for
calculations in a large range of beam energies. The parameter space of the
model is explored, and constrained by comparison with the experimental data for
bulk observables from SPS and the phase I beam energy scan at RHIC. The favored
parameter values depend on energy, but allow to extract the effective value of
the shear viscosity coefficient over entropy density ratio in the
fluid phase for the whole energy region under investigation. The estimated
value of increases with decreasing collision energy, which may
indicate that of the quark-gluon plasma depends on baryochemical
potential .Comment: minor changes in the text, results for constant eta*T/w added.
Version accepted for publication in Phys. Rev.
Lateral-directional control of the x-15 airplane
Lateral directional control and stability characteristics of X-15 aircraf
Improved mirror position estimation using resonant quantum smoothing
Quantum parameter estimation, the ability to precisely obtain a classical
value in a quantum system, is very important to many key quantum technologies.
Many of these technologies rely on an optical probe, either coherent or
squeezed states to make a precise measurement of a parameter ultimately limited
by quantum mechanics. We use this technique to theoretically model, simulate
and validate by experiment the measurement and precise estimation of the
position of a cavity mirror. In non-resonant systems, the achieved estimation
enhancement from quantum smoothing over optimal filtering has not exceeded a
factor two, even when squeezed state probes were used. Using a coherent state
probe, we show that using quantum smoothing on a mechanically resonant
structure driven by a resonant forcing function can result significantly
greater improvement in parameter estimation than with non-resonant systems. In
this work, we show that it is possible to achieve a smoothing improvement by a
factor in excess of three times over optimal filtering. By using intra-cavity
light as the probe we obtain finer precision than has been achieved with the
equivalent quantum resources in free-space.Comment: 14 pages, 9 figures and 1 tabl
The Penn State ORSER system for processing and analyzing ERTS and other MSS data
The author has identified the following significant results. The office for Remote Sensing of Earth Resources (ORSER) of the Space Science and Engineering Laboratory at the Pennsylvania State University has developed an extensive operational system for processing and analyzing ERTS-1 and similar multispectral data. The ORSER system was developed for use by a wide variety of researchers working in remote sensing. Both photointerpretive techniques and automatic computer processing methods have been developed and used, separately and in a combined approach. A remote Job Entry system permits use of an IBM 370/168 computer from any compatible remote terminal, including equipment tied in by long distance telephone connections. An elementary cost analysis has been prepared for the processing of ERTS data
Magnetometry with entangled atomic samples
We present a theory for the estimation of a scalar or a vector magnetic field
by its influence on an ensemble of trapped spin polarized atoms. The atoms
interact off-resonantly with a continuous laser field, and the measurement of
the polarization rotation of the probe light, induced by the dispersive
atom-light coupling, leads to spin-squeezing of the atomic sample which enables
an estimate of the magnetic field which is more precise than that expected from
standard counting statistics. For polarized light and polarized atoms, a
description of the non-classical components of the collective spin angular
momentum for the atoms and the collective Stokes vectors of the light-field in
terms of effective gaussian position and momentum variables is practically
exact. The gaussian formalism describes the dynamics of the system very
effectively and accounts explicitly for the back-action on the atoms due to
measurement and for the estimate of the magnetic field. Multi-component
magnetic fields are estimated by the measurement of suitably chosen atomic
observables and precision and efficiency is gained by dividing the atomic gas
in two or more samples which are entangled by the dispersive atom-light
interaction.Comment: 8 pages, 11 figure
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