Results 21 to 30 of about 165,391 (125)

Nonstationary Gravitational Lenses and the Fermat Principle [PDF]

Astrophys.J.398:425,1992, 1992
We apply Perlick's (1990a) rigorous formulation of the Fermat principle in arbitrary spacetimes to prove the correctness of the description of gravitational lensing by gravitational waves, given in the literature using the scalar and vector formalisms.
arxiv   +1 more source

The creation of multiple images by a gravitational wave [PDF]

Proceedings of the Pacific Conference on Gravitation and Cosmology, Seoul, Korea 1996, Y.M. Cho, C.H. Lee and S.-W. Kim eds. (World Scientific, Singapore, 1998), 1996
We describe gravitational lensing by a gravitational wave, in the regime in which multiple images of a light source are created. We adapt the vector formalism employed for ordinary gravitational lenses to the case of a non-stationary spacetime, and we derive an approximate condition for multiple imaging.
arxiv   +1 more source

Strong field limit analysis of gravitational retro-lensing [PDF]

Phys.Rev. D69 (2004) 063004, 2003
We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic
arxiv   +1 more source

Gravitational Lensing by Cosmic String Loops [PDF]

Phys.Rev.D54:4780-4791,1996, 1996
We calculate the deflection of a light ray caused by the gravitational field of a cosmic string loop in the weak field limit and reduce the problem to a single quadrature over a time slice of the loop's world sheet. We then apply this formalism to the problem of gravitational lensing by cosmic string loops.
arxiv   +1 more source

Exploring Weak Gravitational Lensing Effects by a Regular Black Hole

Spektra: Jurnal Fisika dan Aplikasinya
Gravitational lensing is one of the physical consequences of Einstein’s general theory of relativity, which has been observationally confirmed. This work aims to study the weak gravitational lensing scenario where the lens is a spherically symmetric ...
A. K. Durrani, H. S. Ramadhan
doaj   +1 more source

An Exact Universal Gravitational Lensing Equation [PDF]

Phys.Rev.D59:124001,1999, 1998
We first define what we mean by gravitational lensing equations in a general space-time. A set of exact relations are then derived that can be used as the gravitational lens equations in all physical situations. The caveat is that into these equations there must be inserted a function, a two-parameter family of solutions to the eikonal equation, not ...
arxiv   +1 more source

Staged ecologies: Aesthetics, nature and infrastructure in the late‐modern metropolis

Transactions of the Institute of British Geographers, EarlyView.
Short Abstract This paper examines the relationship between urban nature and landscape design within a £1.5 billion regeneration project that is currently unfolding in Thamesmead, a town in south‐east London. It develops the notion of ‘staged ecologies’ to examine how urban nature is being spatially and aesthetically arranged across the town's ...
Zuhri James
wiley   +1 more source

Plasma lensing in comparison to gravitational lensing -- Formalism and degeneracies [PDF]

arXiv, 2020
Gravitational and plasma lensing share the same mathematical formalism in the limit of geometrical optics. Both phenomena can be effectively described by a projected, two-dimensional deflection potential whose gradient causes an instantaneous light deflection in a single, thin lens plane.
arxiv  

Three-dimensional weak gravitational lensing of the 21-cm radiation background [PDF]

arXiv, 2022
We study weak gravitational lensing by the cosmic large-scale structure of the 21-cm radiation background in the 3d-weak lensing formalism. The interplay between source distance measured at finite resolution, visibility and lensing terms is analysed in detail and the resulting total covariance $C_{\ell}(k,k')$ is derived.
arxiv  

Gauge-Invariant Formalism of Cosmological Weak Lensing [PDF]

JCAP 04 (2018) 029, 2018
We present the gauge-invariant formalism of cosmological weak lensing, accounting for all the relativistic effects due to the scalar, vector, and tensor perturbations at the linear order. While the light propagation is fully described by the geodesic equation, the relation of the photon wavevector to the physical quantities requires the specification ...
arxiv   +1 more source