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A numerical study of the Einstein field equations, based on the 3+1 foliation of the spacetime, is presented. A pseudo-spectral technique has been employed for simulations in vacuum, within two different formalisms, namely the…

General Relativity and Quantum Cosmology · Physics 2021-06-09 Claudio Meringolo , Sergio Servidio , Pierluigi Veltri

Spontaneous scalarization is a mechanism that allows a scalar field to go undetected in weak gravity environments and yet develop a nontrivial configuration in strongly gravitating systems. At the perturbative level it manifests as a…

General Relativity and Quantum Cosmology · Physics 2022-03-14 Hector O. Silva , Andrew Coates , Fethi M. Ramazanoğlu , Thomas P. Sotiriou

We solve the Killing spinor equations of ${\cal N}=1$ supergravity, with four supercharges, coupled to any number of vector and scalar multiplets in all cases. We find that backgrounds with N=1 supersymmetry admit a null, integrable,…

High Energy Physics - Theory · Physics 2009-10-09 U. Gran , J. Gutowski , G. Papadopoulos

By using the ghost imaging technique, we experimentally demonstrate the reconstruction of the diffraction pattern of a {\em pure phase} object by using the classical correlation of incoherent thermal light split on a beam splitter. The…

Quantum Physics · Physics 2007-05-23 M. Bache , D. Magatti , A. Gatti , E. Brambilla , F. Ferri , L. A. Lugiato

We investigate experimentally fundamental properties of coherent ghost imaging using spatially incoherent beams generated from a pseudo-thermal source. A complementarity between the coherence of the beams and the correlation between them is…

Quantum Physics · Physics 2007-05-23 A. Gatti , M. Bache , D. Magatti , E. Brambilla , F. Ferri , L. A. Lugiato

High-resolution ghost image and ghost diffraction experiments are performed by using a single source of thermal-like speckle light divided by a beam splitter. Passing from the image to the diffraction result solely relies on changing the…

In computational ghost imaging the object is illuminated with a sequence of known patterns, and the scattered light is collected using a detector that has no spatial resolution. Using those patterns and the total intensity measurement from…

Image and Video Processing · Electrical Eng. & Systems 2021-12-16 Harry Penketh , William L Barnes , Jacopo Bertolotti

We propose a model in which a spliced vector bundle (with an arbitrary number of gauge structures in the splice) possesses a geometry which do not split. The model employs connection 1-forms with values in a space-product of Lie algebras,…

High Energy Physics - Theory · Physics 2008-11-26 O. Megged

We prove that many cosmological models characterized by vectors nonminimally coupled to the curvature (such as the Turner-Widrow mechanism for the production of magnetic fields during inflation, and models of vector inflation or vector…

Cosmology and Nongalactic Astrophysics · Physics 2010-01-07 Burak Himmetoglu , Carlo R. Contaldi , Marco Peloso

Naked singularities appear naturally in dynamically evolving solutions of Einstein equations involving gravitational collapse of radiation, dust and perfect fluids, provided the rate of accretion is less than a critical value. We propose…

High Energy Physics - Theory · Physics 2009-10-22 Sandip K. Chakrabarti , Pankaj S. Joshi

Reduction algebras are known by many names in the literature, including step algebras, Mickelsson algebras, Zhelobenko algebras, and transvector algebras, to name a few. These algebras, realized by raising and lowering operators, allow for…

Representation Theory · Mathematics 2023-12-08 Jonas T. Hartwig , Dwight Anderson Williams

In this paper, we develop the numerical inverse scattering transform (NIST) for solving the derivative nonlinear Schrodinger (DNLS) equation. The key technique involves formulating a Riemann-Hilbert problem (RHP) that is associated with the…

Numerical Analysis · Mathematics 2024-10-07 Shikun Cui , Zhen Wang

An effective action of ghost condensate with higher derivatives creates a source of gravity and mimics a dark matter in spiral galaxies. We present a spherically symmetric static solution of Einstein--Hilbert equations with the ghost…

General Relativity and Quantum Cosmology · Physics 2007-05-23 V. V. Kiselev

The $\gamma$-metric is a static, axially-symmetric singular solution of the vacuum Einstein's equations without an event horizon. This is a two-parameter family of solutions, generic values of one of which (called $\gamma$) measure the…

General Relativity and Quantum Cosmology · Physics 2022-08-24 Rajibul Shaikh , Suvankar Paul , Pritam Banerjee , Tapobrata Sarkar

Classical ghost imaging is a computational imaging technique that employs patterned illumination. It is very similar in concept to the single-pixel camera in that an image may be reconstructed from a set of measurements even though all…

Image and Video Processing · Electrical Eng. & Systems 2021-03-10 Andrew M. Kingston , Wilfred K. Fullagar , Glenn R. Myers , Daishi Adams , Daniele Pelliccia , David M. Paganin

Classical ghost imaging is a new paradigm in imaging where the image of an object is not measured directly with a pixelated detector. Rather, the object is subject to a set of illumination patterns and the total interaction of the object,…

Image and Video Processing · Electrical Eng. & Systems 2023-08-02 Andrew M. Kingston , Lindon Roberts , Alaleh Aminzadeh , Daniele Pelliccia , Imants D. Svalbe , David M. Paganin

An exact, axially symmetric solution to the Einstein-Klein-Gordon field equations is employed to model the dark matter in spiral galaxies. The extended rotation curves from a previous analysis are used to fit the model and a very good…

Astrophysics · Physics 2007-05-23 F. S. Guzman , T. Matos , H. Villegas-Brena

Ghost imaging is an unconventional optical imaging technique that reconstructs the shape of an object combining the measurement of two signals: one that interacted with the object, but without any spatial information, the other containing…

Ghost imaging is demonstrated using a poly-energetic reactor source of thermal neutrons. The method presented enables position resolution to be incorporated, into a variety of neutron instruments that are not position resolving. In an…

Image and Video Processing · Electrical Eng. & Systems 2020-05-27 Andrew M. Kingston , Glenn R. Myers , Daniele Pelliccia , Filomena Salvemini , Joseph J. Bevitt , Ulf Garbe , David M. Paganin

We present the first experimental demonstration of ghost imaging realized with intense beams generated by a parametric downconversion interaction seeded with pseudo-thermal light. As expected, the real image of the object is reconstructed…

Quantum Physics · Physics 2009-11-13 E. Puddu , A. Andreoni , I. P. Degiovanni , M. Bondani , S. Castelletto