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We reply to the criticisms moved in [1] against our results presented in [2]. In particular, we show that our fractal model has none of the problems claimed in [1]. The latters can be addressed to the overlooked nonlinear behaviour of the…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-10 Leonardo Cosmai , Giuseppe Fanizza , Francesco Sylos Labini , Luciano Pietronero , Luigi Tedesco

Recently, Zhang et al. (Phys. Rev. Lett. 91, 157404 (2003)) have demonstrated that an amphoteric refraction, i. e. both positive and negative refraction, may prevail at the interface of two uniaxial anisotropic crystals when their optical…

Condensed Matter · Physics 2007-05-23 H. -F. Yau , J. -P. Liu , B. Ke , C. -H. Kuo , Z. Ye

The null geodesics that describe photon orbits in the spacetime of a rotating electrically charged black hole (Kerr-Newman) are solved exactly including the contribution from the cosmological constant. We derive elegant closed form…

General Relativity and Quantum Cosmology · Physics 2015-02-27 G. V. Kraniotis

An ultimate universal theory -- a complete theory that accounts, via few and simple first principles, for all the phenomena already observed and that will ever be observed -- has been, and still is, the aspiration of most physicists and…

History and Philosophy of Physics · Physics 2021-03-24 Uri Ben-Ya'acov

We found strong similarities between the gravitational lensing and the conventional optical lensing. The similarities imply a graded refractive index description of the light deflection in gravitational field. We got a general approach to…

General Relativity and Quantum Cosmology · Physics 2009-11-13 Xing-Hao Ye , Qiang Lin

When light from a distant source object, like a galaxy or a supernova, travels towards us, it is deflected by massive objects that lie on its path. When the mass density of the deflecting object exceeds a certain threshold, multiple, highly…

Cosmology and Nongalactic Astrophysics · Physics 2019-09-06 Jenny Wagner

It is shown that negative electric permittivity and magnetic permeability recently discovered in a photonic crystal in the vicinity of the Gamma-point are properties of propagating modes only. The evanescent modes rather decay than increase…

Materials Science · Physics 2007-05-23 A. L. Efros , C. Y. Li , A. L. Pokrovsky

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…

Cosmology and Nongalactic Astrophysics · Physics 2020-07-01 Jenny Wagner , Xinzhong Er

It is well known that the resolution method (for propositional logic) is complete. However, completeness proofs found in the literature use an argument by contradiction showing that if a set of clauses is unsatisfiable, then it must have a…

Logic in Computer Science · Computer Science 2017-01-11 Jean Gallier

Many physicists have thought that absolute time became otiose with the introduction of Special Relativity. William Lane Craig disagrees and argues that although relativity is empirically adequate within a domain of application, relativity…

History and Philosophy of Physics · Physics 2021-09-20 Daniel Linford

One of the key insights in the emerging field of non-Hermitian photonics is that well-established concepts like the laser can be operated in reverse to realize a 'coherent perfect absorber' (CPA). While conceptually appealing, such CPAs are…

We study gravitational lensing by clusters of galaxies in the context of the generic class of unconventional gravity theories of the scalar--tensor type. For positive energy scalar fields with any dynamics, the bending of light by a weakly…

Astrophysics · Physics 2010-11-01 Jacob D. Bekenstein , Robert H. Sanders

Strong, symmetrically focusing plasma lenses are promising for accommodating the small beams associated with plasma-based accelerators and collider final foci. However, while focusing with active and passive plasma lenses has been…

In these lectures I give an overview of gravitational lensing, concentrating on theoretical aspects, including derivations of some of the important results. Topics covered include the determination of surface mass densities of intervening…

Cosmology and Nongalactic Astrophysics · Physics 2017-03-08 Alan Heavens

The distortion of the spacetime structure in the surroundings of black holes affects the trajectories of light rays. As a consequence, black holes can act as gravitational lenses. Observations of type Ia supernovas, show that our Universe…

General Relativity and Quantum Cosmology · Physics 2016-01-14 Ernesto F. Eiroa , Carlos M. Sendra

Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves.…

General Relativity and Quantum Cosmology · Physics 2010-10-12 Yousuke Itoh , Toshifumi Futamase , Makoto Hattori

Discoveries in the last few years have revolutionized our knowledge of the universe and our ideas of its ultimate fate. Measurements of the expansion of the universe show that it is not slowing down under normal gravity but accelerating due…

Astrophysics · Physics 2007-05-23 Eric V. Linder

In this paper, we discuss the gravitational field of ultrarelativistic extended spinning objects. For this purpose, we use a solution of the linearized gravitational equations obtained in the frame where such an object is translationally at…

General Relativity and Quantum Cosmology · Physics 2022-10-05 Valeri P. Frolov , Alex Koek

Has the ten-year old quest for the optical superlens, based on Veselago's hypothesis of negative refraction, been a chimera? We argue that Pendry's alternative prescription of the silver superlens is nothing more than an application of the…

Optics · Physics 2010-04-16 George Christou , Christos Mias

The absorption and extinction spectra of sub-wavelength cylinder arrays are shown to present two different kind of resonances. Close to the Rayleigh anomalies, the diffractive coupling with the lattice periodicity leads to sharp peaks in…

Optics · Physics 2007-05-23 Marine Laroche , Raquel Gomez-Medina , Juan Jose Saenz
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