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In weak lensing by large-scale structure, the thin-lens approximation may break down, and low-density extended structures may not be well approximated by multiple thin-lens planes. In this case, the deflection can be derived by instead assuming that the gravitational potential is slowly varying everywhere (for this reason, this approximation is ...
In 1963 Yu. G. Klimov, S. Liebes, and Sjur Refsdal recognized independently that quasars are an ideal light source for the gravitational lens effect. [23] It was not until 1979 that the first gravitational lens would be discovered. It became known as the "Twin QSO" since it initially looked like two identical quasistellar objects.
The key difference between an embedded lens and a traditional lens is that the mass of a standard lens contributes to the mean of the cosmological density, whereas that of an embedded lens does not. Consequently, the gravitational potential of an embedded lens has a finite range, i.e., there is no lensing effect outside of the void.
Let us assume a static, spherically symmetric perfect fluid. The metric components are similar to those for the Schwarzschild metric: [2] = = By the perfect fluid assumption, the stress-energy tensor is diagonal (in the central spherical coordinate system), with eigenvalues of energy density and pressure:
The two 3-km (1.9 mi) arms are made of a long steel pipe 1.2 m (3.9 ft) in diameter, in which the target residual pressure is about one-thousandth of a billionth of an atmosphere (100 times thinner than in the original Virgo). The residual gas molecules, primarily hydrogen and water, have a limited impact on the laser beams' path.
Strong gravitational lensing is a gravitational lensing effect that is strong enough to produce multiple images, arcs, or Einstein rings. Generally, for strong lensing to occur, the projected lens mass density must be greater than the critical density , that is Σ c r {\displaystyle \Sigma _{cr}} .
The group concentrates especially on the detection and observation of gravitational microlensing events of high magnification, of order 100 or more, as these provide the greatest sensitivity to extrasolar planets.
In the original formulation by Mazur and Mottola, [4] a gravastar is composed of three regions, differentiated by the relationship between pressure p and energy density ρ [jargon]. The central region consists of false vacuum or "dark energy", and in this region p = −ρ. Surrounding it is a thin shell of perfect fluid where p = ρ.