7,823 research outputs found
Weak values and the quantum phase space
We address the issue of how to properly treat, and in a more general setting,
the concept of a weak value of a weak measurement in quantum mechanics. We show
that for this purpose, one must take in account the effects of the measuring
process on the entire phase space of the measuring system. By using coherent
states, we go a step further than Jozsa in a recent paper, and we present an
example where the result of the measurement is symmetrical in the position and
momentum observables and seems to be much better suited for quantum optical
implementation.Comment: 07 pages, accepted for PR
Errors on the inverse problem solution for a noisy spherical gravitational wave antenna
A single spherical antenna is capable of measuring the direction and
polarization of a gravitational wave. It is possible to solve the inverse
problem using only linear algebra even in the presence of noise. The simplicity
of this solution enables one to explore the error on the solution using
standard techniques. In this paper we derive the error on the direction and
polarization measurements of a gravitational wave. We show that the solid angle
error and the uncertainty on the wave amplitude are direction independent. We
also discuss the possibility of determining the polarization amplitudes with
isotropic sensitivity for any given gravitational wave source.Comment: 13 pages, 4 figures, LaTeX2e, IOP style, submitted to CQ
A catalogue of velocities in the cluster of galaxies Abell 85
We present a catalogue of velocities for 551 galaxies (and give the
coordinates of 39 stars misclassified as galaxies in our photometric plate
catalogue) in a region covering about 100'100' (0.940.94 Mpc
for an average redshift of 0.0555, assuming H=50 km s
Mpc) in the direction of the rich cluster Abell 85. This catalogue
includes previously published redshifts by Beers et al. (1991) and Malumuth et
al. (1992), together with our 367 new measurements. A total of 305 galaxies
have velocities in the interval 13350-20000 km s, and will be considered
as members of the cluster. Abell 85 therefore becomes one of the clusters with
the highest number of measured redshifts; its optical properties are being
investigated in a companion paper.Comment: Accepted for publication in A&AS, Table 4 available in electronic
form onl
Pseudophakic Cystoid Macular Edema
Cataract surgery is an efficient procedure, and is generally associated with good visual results. Nevertheless, cystoid macular edema (CME) may develop, and this can result in suboptimal postoperative vision. Many factors are considered to contribute to its development, and although the treatment options depend upon the underlying cause of CME, the usual therapeutic approach for prophylaxis and treatment of CME is directed towards blocking the inflammatory mediators. This article provides a review of possible risk factors, pathogeneses, incidence rates, and methods of diagnosis, as well as the current guidelines for managing CM
Stable Gravastars of Anisotropic Dark Energy
Dynamical models of prototype gravastars made of phantom energy are
constructed, in which an infinitely thin spherical shell of a perfect fluid
with the equation of state divides the whole spacetime
into two regions, the internal region filled with a dark energy (or phantom)
fluid, and the external Schwarzschild region. It is found that in some cases
the models represent the "bounded excursion" stable gravastars, where the thin
shell is oscillating between two finite radii, while in other cases they
collapse until the formation of black holes or normal stars. In the phase
space, the region for the "bounded excursion" gravastars is very small in
comparison to that of black holes, but not empty, as found in our previous
papers. Therefore, although the existence of gravastars can not be completely
excluded from current analysis, the opposite is not possible either, that is,
even if gravastars exist, they do not exclude the existence of black holes.Comment: 35 pages, 43 figures, added some clarifying texts and corrected some
typos, accepted for publication in JCA
- …