The Method of Images in Cosmology

31 pages, 18 figures31 pages, 18 figuresWe apply the method of images to the exact initial data for cosmological models that contain a number of regularly arranged discrete masses. This allows us to join cosmological regions together by throats, and to construct wormholes in the initial data. These wormholes allow for the removal of the asymptotically flat "flange" regions that would otherwise exist on the far side of black holes. The method of images also provides us with a way to investigate the definition of mass is cosmology, and the cosmological consequences of the gravitational interaction energies between massive objects. We find evidence that the interaction energies within clusters of massive objects do indeed appear to contribute to the total energy budget in the cosmological regions of the space-time

Probing the Binary Black Hole Merger Regime with Scalar Perturbations

We present results obtained by scattering a scalar field off the curved background of a coalescing binary black hole system. A massless scalar field is evolved on a set of fixed backgrounds, each provided by a spatial hypersurface generated numerically during a binary black hole merger. We show that the scalar field scattered from the merger region exhibits quasinormal ringing once a common apparent horizon surrounds the two black holes. This occurs earlier than the onset of the perturbative regime as measured by the start of the quasinormal ringing in the gravitational waveforms. We also use the scalar quasinormal frequencies to associate a mass and a spin with each hypersurface, and observe the compatibility of this measure with the horizon mass and spin computed from the dynamical horizon framework.Comment: 10 Pages and 6 figure

Cavernous haemangioma of the external auditory canal: clinical case and review of the literature

Although benign vascular lesions are frequent in the head and the neck region, clinical evidence of cavernous haemangioma of the external auditory canal is extremely rare; when present, the lesion invades the middle ear space. Herein, a rare case of a soft mass filling the external auditory canal, not involving the tympanic membrane, in a symptomatic 59-year-old male is described. Clinical and audiological characteristics, imaging studies and surgical treatment with histological evaluation are reported, which led to a diagnosis of a cavernous haemangioma. This is only the seventh case described in the literature, to date, not involving the tympanic membrane and the middle ear space. In addition, a review has been made of the relevant literature with respect to epidemiology, presentation, evaluation, pathology, and management options for haemangiomas arising in the external auditory canal

On the threshold of effective well infant nursery hearing screening in Western Sicily

Objective: To determine the feasibility and effectiveness of well-infant nursery hearing screening programme for the early identification of hearing impairment, based on transient evoked otoacoustic emission (TEOAE) with a high “screen sensitivity” reducing the number of more expensive secondary level exams. Methods: The newborns were screened by non-specialist health workers in well babies nursery at the twentieth day of life for 6 years consecutive. Based on PASS/FAIL criteria and presence/absence of audiological risk factors the newborns were divided into four groups each one with its personal step program: G1- PASS without risk factor, free to go home; G2 - PASS with risk factor, retest at the age of 7 months; G3 - FAIL without risk factor, re-screening after 2 weeks for a maximum of four times before audiology assessment; G4 - FAIL with risk factor, retest after 2 weeks. Results: The coverage rate increased progressively from 89.8% to 92%. The referral rate was 1.51% after second stage with a specificity value of 98.78%. The four-stage screening performed for G3 reduced the numbers of global audiology assessment to 0.91% with a final global specificity of 99.4+0.4%. Conclusion: Less than 1% of infants underwent audiological assessment; the false positives resulted 0.62% with hearing loss global incidence of 2.95/1000 and a mean age of confirmation of 3.5 months of age. It is reasonable to think that this screening program could be implement to overall forty-two Western Sicily birth centres within few years

On the Possibility of Quantum Gravity Effects at Astrophysical Scales

The nonperturbative renormalization group flow of Quantum Einstein Gravity (QEG) is reviewed. It is argued that at large distances there could be strong renormalization effects, including a scale dependence of Newton's constant, which mimic the presence of dark matter at galactic and cosmological scales.Comment: LaTeX, 18 pages, 4 figures. Invited contribution to the Int. J. Mod. Phys. D special issue on dark matter and dark energ

Cosmology with variable parameters and effective equation of state for Dark Energy

A cosmological constant, Lambda, is the most natural candidate to explain the origin of the dark energy (DE) component in the Universe. However, due to experimental evidence that the equation of state (EOS) of the DE could be evolving with time/redshift (including the possibility that it might behave phantom-like near our time) has led theorists to emphasize that there might be a dynamical field (or some suitable combination of them) that could explain the behavior of the DE. While this is of course one possibility, here we show that there is no imperative need to invoke such dynamical fields and that a variable cosmological constant (including perhaps a variable Newton's constant too) may account in a natural way for all these features.Comment: LaTeX, 9 pages, 1 figure. Talk given at the 7th Intern. Workshop on Quantum Field Theory Under the Influence of External Conditions (QFEXT 05

A quasi-static approach to structure formation in black hole universes

JD and TC both acknowledge support from the STFC under grant STFC ST/N504257/1