Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Building Information Modelling (BIM) : a summary of some UK experiences as guide to adoption in Nigeria

Building information modelling (BIM) is a term that has been echoed around the world by researchers and practitioners alike. This is a new methodology (essentially electronic capture and focussed, timely distribution of relevant data) of project delivery that improves efficiency and quality of work. Although the word 'building' is used, BIM is equally applicable to civil engineering, utilities and infrastructure projects. Also, the word 'modelling' applies to the broad spectrum of process application not simply models produced by 3d software packages. The most important element in BIM is the 'information' and its beneficial capture and repeat usage. Every sector of the world economy is just looking for ways to produce more with fewer resources or making best use of the resources available. This paradigm shift has brought about the adoption of BIM in the construction industry. This paper will define BIM in simple terms; highlight its benefits and barriers; rationalise its workability, maturity levels and general ideas that it is based upon. The paper will also articulate some actual experiences from the UK at both the government and organisational level and the challenges overcome and some benefits achieved. Just like any other technology or methodology, BIM relies on collaboration for its successful implementation. This collaboration will create an avenue for construction teams to produce and make use of consistent unambiguous information, which will improve the overall efficiency in project delivery. For many people the question still remains. Will this be a solution to the all the problems in the industry? Or will it only solve particular problems? Just like every technology using it correctly will definitely yield benefits. Governments in many countries have recognised the usefulness of BIM and have intervened to make its implementation possible. As a developing country, Nigeria should not be far from making such efforts. There is need for construction industry to take proactive steps to overcome its problems. BIM implementation may not be a panacea to all the problems in the construction industry but it will surely make it better. Construction professionals may look at this idea with scepticism echoed, although it is now being overcome in countries adopting BIM. The earlier they realise that BIM will be the future of the industry the better