Perturbations in the Kerr-Newman Dilatonic Black Hole Background: I. Maxwell waves

In this paper we analyze the perturbations of the Kerr-Newman dilatonic black hole background. For this purpose we perform a double expansion in both the background electric charge and the wave parameters of the relevant quantities in the Newman-Penrose formalism. We then display the gravitational, dilatonic and electromagnetic equations, which reproduce the static solution (at zero order in the wave parameter) and the corresponding wave equations in the Kerr background (at first order in the wave parameter and zero order in the electric charge). At higher orders in the electric charge one encounters corrections to the propagations of waves induced by the presence of a non-vanishing dilaton. An explicit computation is carried out for the electromagnetic waves up to the asymptotic form of the Maxwell field perturbations produced by the interaction with dilatonic waves. A simple physical model is proposed which could make these perturbations relevant to the detection of radiation coming from the region of space near a black hole.Comment: RevTeX, 36 pages in preprint style, 1 figure posted as a separate PS file, submitted to Phys. Rev.

Subtraction of Newtonian Noise Using Optimized Sensor Arrays

Fluctuations in the local Newtonian gravitational field present a limit to high precision measurements, including searches for gravitational waves using laser interferometers. In this work, we present a model of this perturbing gravitational field and evaluate schemes to mitigate the effect by estimating and subtracting it from the interferometer data stream. Information about the Newtonian noise is obtained from simulated seismic data. The method is tested on causal as well as acausal implementations of noise subtraction. In both cases it is demonstrated that broadband mitigation factors close to 10 can be achieved removing Newtonian noise as a dominant noise contribution. The resulting improvement in the detector sensitivity will substantially enhance the detection rate of gravitational radiation from cosmological sources.Comment: 29 pages, 11 figure

Force measurement during spinal mobilisation

PhDSpinal mobilisation or manipulation techniques are frequently used by physiotherapists in the treatment of musculoskeletal disorders. Despite the reliance on these techniques in clinical practice, there is little scientific evidence to substantiate their use. A standard mobilisation couch was instrumented to enable measurement of the forces applied to the trunk during mobilisation of the lumbar spine. Six load cells were incorporated into the couch frame and linked to a personal computer to facilitate data collection. The couch allowed the assessment of the magnitude of the mobilisation force, its direction and the variation in applied load over time. The system was found to be reliable and sensitive over the range of forces applied during mobilisation. The system was used to collect data from a sample of 30 experienced therapists to evaluate repeatability and reproducibility during the application of four grades of a posteroanterior mobilisation and an End Feel, on the third lumbar vertebra. Whilst some therapists demonstrated considerable variation in the forces applied both within one measurement session and over a two week period, others were found to be relatively consistent. The range of forces used by different therapists when performing the same technique was substantial ranging between 63 N and 347 N for a Grade IV mobilisation. A study was carried out involving 26 young healthy subjects, to determine the characteristics of a mobilisation force applied to an asymptomatic spine. A further study was undertaken involving a clinical sample of 16 patients, aged between 47- 64 years, to evaluate the effect of age related degenerative changes of the lumbar spine on the application of these techniques. The magnitude of the mobilisation force was found to be similar for the healthy and the patient groups with median forces of 175 N and 171 N during a Grade IV procedure, respectively. However, the forces applied to the patient group exhibited a statistically significantly smaller amplitude and higher frequency of oscillation than the healthy group for the same procedure (p < 0.01). Such measurements are essential for the assessment of the efficacy of these techniques in clinical practice.Chartered Society of Physiotherap

BBO and the Neutron-Star-Binary Subtraction Problem

The Big Bang Observer (BBO) is a proposed space-based gravitational-wave (GW) mission designed primarily to search for an inflation-generated GW background in the frequency range 0.1-1 Hz. The major astrophysical foreground in this range is gravitational radiation from inspiraling compact binaries. This foreground is expected to be much larger than the inflation-generated background, so to accomplish its main goal, BBO must be sensitive enough to identify and subtract out practically all such binaries in the observable universe. It is somewhat subtle to decide whether BBO's current baseline design is sufficiently sensitive for this task, since, at least initially, the dominant noise source impeding identification of any one binary is confusion noise from all the others. Here we present a self-consistent scheme for deciding whether BBO's baseline design is indeed adequate for subtracting out the binary foreground. We conclude that the current baseline should be sufficient. However if BBO's instrumental sensitivity were degraded by a factor 2-4, it could no longer perform its main mission. It is impossible to perfectly subtract out each of the binary inspiral waveforms, so an important question is how to deal with the "residual" errors in the post-subtraction data stream. We sketch a strategy of "projecting out" these residual errors, at the cost of some effective bandwidth. We also provide estimates of the sizes of various post-Newtonian effects in the inspiral waveforms that must be accounted for in the BBO analysis.Comment: corrects some errors in figure captions that are present in the published versio