5,984 research outputs found
Charged Particle Dynamics in the Field of a Slowly Rotating Compact Star
We study the dynamics of a charged particle in the field of a slowly rotating
compact star in the gravitoelectromagnetic approximation to the geodesic
equation . The star is assumed to be surrounded by an ideal, highly conducting
plasma (taken as a magnetohydrodynamic fluid) with a stationary, axially
symmetric electromagnetic field. The general relativistic Maxwell equations are
solved to obtain the effects of the background spacetime on the electromagnetic
field in the linearized Kerr spacetime. The equations of motion are then set up
and solved numerically to incorporate the gravitational as well as the
electromagnetic effects. The analysis shows that in the slow rotation
approximation the frame dragging effects on the electromagnetic field are
absent. However the particle is directly effected by the rotating gravitational
source such that close to the star the gravitational and electromagnetic field
produce contrary effects on the particle's trajectory.Comment: 10 pages, 6 figures in B & W PostScript Forma
Fiber R and D for the CMS HCAL
This paper documents the fiber R and D for the CMS hadron barrel calorimeter
(HCAL). The R and D includes measurements of fiber flexibility, splicing,
mirror reflectivity, relative light yield, attenuation length, radiation
effects, absolute light yield, and transverse tile uniformity. Schematics of
the hardware for each measurement are shown. These studies are done for
different diameters and kinds of multiclad fiber.Comment: 23 pages, 30 Figures 89 pages, 41 figures, corresponding author: H.
Budd, [email protected]
A Collection of Optimal Control Problems
In this work, a collection of elliptic and parabolic control problems with control and state constraints is described, focusing on the discretization techniques which yield to Nonlinear Programming (NLP) problems having large, sparse and structured Hessian and Jacobian matrices. The collection includes 25 elliptic and parabolic control problem, which are described in detail, reporting the sparsity pattern of the Hessian and Jacobian matrices. The figures depicting the discrete solutions of the elliptic problems are also reported. The AMPL models of the elliptic control problems can be downloaded from the prof. Mittelmann's web page http://plato.asu.edu/ftp/ampl_files/ellip_ampl/ while the ones related to the parabolic ones are downloadable from http://dm.unife.it/~bonettini/ip_pcg/controllo.ht
Stability diagrams for Landau damping
Coherent modes which are present when there is no incoherent tune spread may be absent when such a spread exists. Such modes are``Landau damped.'' There is instead an incoherent spectrum, a continuum of an infinite number of frequencies, which will decohere (filament), thus not leading to collective instabilities. A stability diagram indicates when Landau damping will be effective. It divides the effective impedance plane, or equivalently the plane of coherent frequency in the absence of tune spread, into regions. The region which contains +i/infinity corresponds to instability. Thus, one can substitute a simpler computation (finding discrete eigenvalues) for a more complex computation (solving an eigenvalue system with both a discrete and a continuous eigenvalue spectrum). We present stability diagrams assuming a linear tune shift with amplitude, allowing tune spread in two transverse planes or in the longitudinal plane alone. When there is longitudinal tune spread, this can not be done exactly, and we describe approximations which make the computation tractable
Doppler Effects from Bending of Light Rays in Curved Space-Times
We study Doppler effects in curved space-time, i.e. the frequency shifts
induced on electromagnetic signals propagating in the gravitational field. In
particular, we focus on the frequency shift due to the bending of light rays in
weak gravitational fields. We consider, using the PPN formalism, the
gravitational field of an axially symmetric distribution of mass. The zeroth
order, i.e. the sphere, is studied then passing to the contribution of the
quadrupole moment, and finally to the case of a rotating source. We give
numerical estimates for situations of physical interest, and by a very
preliminary analysis, we argue that analyzing the Doppler effect could lead, in
principle, in the foreseeable future, to the measurement of the quadrupole
moment of the giant planets of the Solar System.Comment: 16 pages, 2 EPS figures; to appear in the International Journal of
Modern Physics
A post-Keplerian parameter to test gravito-magnetic effects in binary pulsar systems
We study the pulsar timing, focusing on the time delay induced by the
gravitational field of the binary systems. In particular, we study the
gravito-magnetic correction to the Shapiro time delay in terms of Keplerian and
post-Keplerian parameters, and we introduce a new post-Keplerian parameter
which is related to the intrinsic angular momentum of the stars. Furthermore,
we evaluate the magnitude of these effects for the binary pulsar systems known
so far. The expected magnitude is indeed small, but the effect is important per
se.Comment: 6 pages, RevTeX, 1 eps figure, accepted for publication in Physical
Review D; references adde
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