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Astronomical observations in the electromagnetic window - microwave, radio and optical - have revealed that most of the Universe is dark. The only reason we know that dark matter exists is because of its gravitational influence on luminous matter. It is plausible that a small fraction of that dark matter is clumped, and strongly gravitating. Such systems are potential sources of gravitational radiation that can be observed with a world-wide network of gravitational wave antennas. Electromagnetic astronomy has also revealed objects and phenomena - supernovae, neutron stars, black holes and the big bang - that are without doubt extremely strong emitters of the radiation targeted by the gravitational wave interferometric and resonant bar detectors. In this talk I will highlight why gravitational waves arise in Einsteins theory, how they interact with matter, what the chief astronomical sources of the radiation are, and in which way by observing them we can gain a better understanding of the dark and dense Universe.
We present novel analytical solutions for linear-order gravitational waves or tensor perturbations in a flat Friedmann-Robertson-Walker universe containing two perfect fluids, radiation and pressureless dust, and allowing for neutrino anisotropic str
In this review paper we investigate the connection between gravity and electromagnetism from Faraday to the present day. The particular focus is on the connection between gravitational and electromagnetic radiation. We discuss electromagnetic radiati
Cherenkov radiation may occur whenever the source is moving faster than the waves it generates. In a radiation dominated universe, with equation-of-state $w = 1/3$, we have recently shown that the Bardeen scalar-metric perturbations contribute to the
Using the Sparling form and a geometric construction adapted to spacetimes with a 2-dimensional isometry group, we analyse a quasi-local measure of gravitational energy. We then study the gravitational radiation through spacetime junctions in cylindr
Gravitational waves from binary neutron star inspirals have been detected along with the electromagnetic transients coming from the aftermath of the merger in GW170817. However, much is still unknown about the post-merger dynamics that connects these