The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yi Xie - One of the best experts on this subject based on the ideXlab platform.
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time delay of photons coupled to Weyl Tensor in a regular phantom black hole
European Physical Journal C, 2020Co-Authors: Yi XieAbstract:Time delay of the photons coupled to the Weyl Tensor in a regular phantom black hole is investigated in both weak and strong deflection gravitational lensing. We find that the time delay in the weak deflection lensing strongly depends on the phantom hair while the delay in the strong deflection lensing is significantly affected by the hair and the strength of the coupling. We suggest that it is necessary to measure these two kind of time signals for fully understanding and distinguishing such an interaction beyond the standard Einstein–Maxwell theory.
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weak deflection gravitational lensing for photons coupled to Weyl Tensor in a schwarzschild black hole
European Physical Journal C, 2018Co-Authors: Weiguang Cao, Yi XieAbstract:Beyond the Einstein–Maxwell model, electromagnetic field might couple with gravitational field through the Weyl Tensor. In order to provide one of the missing puzzles of the whole physical picture, we investigate weak deflection lensing for photons coupled to the Weyl Tensor in a Schwarzschild black hole under a unified framework that is valid for its two possible polarizations. We obtain its coordinate-independent expressions for all observables of the geometric optics lensing up to the second order in the terms of $$\varepsilon $$ which is the ratio of the angular gravitational radius to angular Einstein radius of the lens. These observables include bending angle, image position, magnification, centroid and time delay. The contributions of such a coupling on some astrophysical scenarios are also studied. We find that, in the cases of weak deflection lensing on a star orbiting the Galactic Center Sgr A*, Galactic microlensing on a star in the bulge and astrometric microlensing by a nearby object, these effects are beyond the current limits of technology. However, measuring the variation of the total flux of two weak deflection lensing images caused by the Sgr A* might be a promising way for testing such a coupling in the future.
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Strong gravitational field time delay for photons coupled to Weyl Tensor in a Schwarzschild black hole
The European Physical Journal C, 2016Co-Authors: Feng-wei Yang, Yi XieAbstract:We analyze strong gravitational field time delay for photons coupled to the Weyl Tensor in a Schwarzschild black hole. By making use of the method of strong deflection limit, we find that these time delays between relativistic images are significantly affected by polarization directions of such a coupling. A practical problem about determination of the polarization direction by observations is investigated. It is found that if the first and second relativistic images can be resolved, the measurement of time delay can more effectively improve detectability of the polarization direction.
Markus B Frob - One of the best experts on this subject based on the ideXlab platform.
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the Weyl Tensor correlator in cosmological spacetimes
arXiv: High Energy Physics - Theory, 2014Co-Authors: Markus B FrobAbstract:We give a general expression for the Weyl Tensor two-point function in a general Friedmann-Lemaitre-Robertson-Walker spacetime. We work in reduced phase space for the perturbations, i.e., quantize only the dynamical degrees of freedom without adding any gauge-fixing term. The general formula is illustrated by a calculation in slow-roll single-field inflation to first order in the slow-roll parameters $\epsilon$ and $\delta$, and the result is shown to have the correct de Sitter limit as $\epsilon, \delta \to 0$. Furthermore, it is seen that the Weyl Tensor correlation function does not suffer from infrared divergences, unlike the two-point functions of the metric and scalar field perturbations. Lastly, we show how to recover the usual Tensor power spectrum from the Weyl Tensor correlation function.
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the Weyl Tensor correlator in cosmological spacetimes
Journal of Cosmology and Astroparticle Physics, 2014Co-Authors: Markus B FrobAbstract:We give a general expression for the Weyl Tensor two-point function in a general Friedmann-Lemaitre-Robertson-Walker spacetime. We work in reduced phase space for the perturbations, i.e., quantize only the dynamical degrees of freedom without adding any gauge-fixing term. The general formula is illustrated by a calculation in slow-roll single-field inflation to first order in the slow-roll parameters and δ, and the result is shown to have the correct de Sitter limit as , δ → 0. Furthermore, it is seen that the Weyl Tensor correlation function in slow-roll does not suffer from infrared divergences, unlike the two-point functions of the metric and scalar field perturbations. Lastly, we show how to recover the usual Tensor power spectrum from the Weyl Tensor correlation function.
Jiliang Jing - One of the best experts on this subject based on the ideXlab platform.
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strong gravitational lensing for photons coupled to Weyl Tensor in a regular phantom black hole
European Physical Journal C, 2018Co-Authors: Ruanjing Zhang, Jiliang JingAbstract:We study strong gravitational lensing for photons coupled to Weyl Tensor in a regular phantom black hole spacetime. It is generally accepted that photons with different polarizations have different trajectories which yields a phenomenon of birefringence. As a result, there are two sets of relativistic images on each side of the object, this is quite different from the uncoupled case in which there is only one set of images. Nevertheless, we focus our attention on the relativistic images on one side of the object and investigate the difference between them by discussing how the coupling constant and phantom hair affect the difference of photon sphere radius, minimum impact parameter and deflection angle. After that, we find that the closer the light gets to the black hole, the larger the deflection angle will be. Then, we investigate the difference in angular image position and relative magnitudes of the first relativistic image between the two types of polarized photons, and find that the two images for different polarizations will separate further and be distinguished more easily in the cases that the phantom hair decreases or the absolute value of the coupling constant increases. Furthermore, the image is brighter when it seats closer to the optical axis.
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strong gravitational lensing for the photons coupled to a Weyl Tensor in a kerr black hole spacetime
Physical Review D, 2017Co-Authors: Songbai Chen, Jiliang Jing, Yang Huang, Shangyun Wang, Shiliang WangAbstract:We present first the equation of motion for the photon coupled to a Weyl Tensor in a Kerr black hole spacetime and then study further the corresponding strong gravitational lensing. We find that black hole rotation makes propagation of the coupled photons more complicated, which brings about some new features for physical quantities, including the marginally circular photon orbit, the deflection angle, the observational gravitational lensing variables, and the time delay between two relativistic images. There is a critical value of the coupling parameter for existence of the marginally circular photon orbit outside the event horizon, which depends on the rotation parameter of the black hole and the polarization direction of the photons. As the value of the coupling parameter nears the critical value, we find that the marginally circular photon orbit for the retrograde photon increases with the rotation parameter, which modifies a common feature of the marginally circular photon orbit in a rotating black hole spacetime since it always decreases monotonously with the rotation parameter in the case without Weyl coupling. Modeling the supermassive central object in our Galaxy as a Kerr black hole, we estimate the numerical values of the observables including time delays between the relativistic images in the strong gravitational lensing of the photons coupled to Weyl Tensor.
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double shadow of a regular phantom black hole as photons couple to the Weyl Tensor
European Physical Journal C, 2016Co-Authors: Yang Huang, Songbai Chen, Jiliang JingAbstract:We have studied the shadow of a regular phantom black hole as photons couple to the Weyl Tensor. We find that due to the coupling photons with different polarization directions propagate along different paths in the spacetime so that there exists a double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The overlap region of the double shadow, the umbra, of the black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to the Weyl Tensor. Our results show that the coupling brings about richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.
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double shadow of a regular phantom black hole as photons couple to Weyl Tensor
arXiv: General Relativity and Quantum Cosmology, 2016Co-Authors: Yang Huang, Songbai Chen, Jiliang JingAbstract:We have studied the shadow of a regular phantom black hole as photons couple to Weyl Tensor. We find that the coupling yields that photons with different polarization directions propagate along different paths in the spacetime so that there exits double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The umbra of black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to Weyl Tensor. Our results show that the coupling brings richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.
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strong gravitational lensing for the photons coupled to Weyl Tensor in a schwarzschild black hole spacetime
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Songbai Chen, Jiliang JingAbstract:We have investigated the strong gravitational lensing for the photons coupled to Weyl Tensor in a Schwarzschild black hole spacetime. We find that in the four-dimensional black hole spacetime the equation of motion of the photons depends not only on the coupling between photon and Weyl Tensor, but also on the polarization direction of the photons. It is quite different from that in the case of the usual photon without coupling to Weyl Tensor in which the equation of motion is independent of the polarization of the photon. Moreover, we find that the coupling and the polarization direction modify the properties of the photon sphere, the deflection angle, the coefficients in strong field lensing, and the observational gravitational lensing variables. Combining with the supermassive central object in our Galaxy, we estimated three observables in the strong gravitational lensing for the photons coupled to Weyl Tensor.
Songbai Chen - One of the best experts on this subject based on the ideXlab platform.
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strong gravitational lensing for the photons coupled to a Weyl Tensor in a kerr black hole spacetime
Physical Review D, 2017Co-Authors: Songbai Chen, Jiliang Jing, Yang Huang, Shangyun Wang, Shiliang WangAbstract:We present first the equation of motion for the photon coupled to a Weyl Tensor in a Kerr black hole spacetime and then study further the corresponding strong gravitational lensing. We find that black hole rotation makes propagation of the coupled photons more complicated, which brings about some new features for physical quantities, including the marginally circular photon orbit, the deflection angle, the observational gravitational lensing variables, and the time delay between two relativistic images. There is a critical value of the coupling parameter for existence of the marginally circular photon orbit outside the event horizon, which depends on the rotation parameter of the black hole and the polarization direction of the photons. As the value of the coupling parameter nears the critical value, we find that the marginally circular photon orbit for the retrograde photon increases with the rotation parameter, which modifies a common feature of the marginally circular photon orbit in a rotating black hole spacetime since it always decreases monotonously with the rotation parameter in the case without Weyl coupling. Modeling the supermassive central object in our Galaxy as a Kerr black hole, we estimate the numerical values of the observables including time delays between the relativistic images in the strong gravitational lensing of the photons coupled to Weyl Tensor.
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double shadow of a regular phantom black hole as photons couple to the Weyl Tensor
European Physical Journal C, 2016Co-Authors: Yang Huang, Songbai Chen, Jiliang JingAbstract:We have studied the shadow of a regular phantom black hole as photons couple to the Weyl Tensor. We find that due to the coupling photons with different polarization directions propagate along different paths in the spacetime so that there exists a double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The overlap region of the double shadow, the umbra, of the black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to the Weyl Tensor. Our results show that the coupling brings about richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.
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double shadow of a regular phantom black hole as photons couple to Weyl Tensor
arXiv: General Relativity and Quantum Cosmology, 2016Co-Authors: Yang Huang, Songbai Chen, Jiliang JingAbstract:We have studied the shadow of a regular phantom black hole as photons couple to Weyl Tensor. We find that the coupling yields that photons with different polarization directions propagate along different paths in the spacetime so that there exits double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The umbra of black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to Weyl Tensor. Our results show that the coupling brings richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.
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strong gravitational lensing for the photons coupled to Weyl Tensor in a schwarzschild black hole spacetime
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Songbai Chen, Jiliang JingAbstract:We have investigated the strong gravitational lensing for the photons coupled to Weyl Tensor in a Schwarzschild black hole spacetime. We find that in the four-dimensional black hole spacetime the equation of motion of the photons depends not only on the coupling between photon and Weyl Tensor, but also on the polarization direction of the photons. It is quite different from that in the case of the usual photon without coupling to Weyl Tensor in which the equation of motion is independent of the polarization of the photon. Moreover, we find that the coupling and the polarization direction modify the properties of the photon sphere, the deflection angle, the coefficients in strong field lensing, and the observational gravitational lensing variables. Combining with the supermassive central object in our Galaxy, we estimated three observables in the strong gravitational lensing for the photons coupled to Weyl Tensor.
A A Coley - One of the best experts on this subject based on the ideXlab platform.
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refinements of the Weyl Tensor classification in five dimensions
arXiv: General Relativity and Quantum Cosmology, 2012Co-Authors: A A Coley, Marcello Ortaggio, Sigbjorn Hervik, Lode WyllemanAbstract:We refine the null alignment classification of the Weyl Tensor of a five-dimensional spacetime. The paper focusses on the algebraically special alignment types {\bf {N}}, {\bf {III}}, {\bf {II}} and {\bf {D}}, while types {\bf {I}} and {\bf {G}} are briefly discussed. A first refinement is provided by the notion of spin type of the components of highest boost weight. Second, we analyze the Segre types of the Weyl operator acting on bivector space and examine the intersection with the spin type classification. We present a full treatment for types {\bf {N}} and {\bf {III}}, and illustrate the classification from different viewpoints (Segre type, rank, spin type) for types {\bf {II}} and {\bf {D}}, paying particular attention to possible nilpotence, which is a new feature of higher dimensions. We also point out other essential differences with the four-dimensional case. In passing, we exemplify the refined classification by mentioning the special subtypes associated to certain important spacetimes, such as Myers-Perry black holes, black strings, Robinson-Trautman spacetimes, and purely electric/magnetic type {\bf {D}} spacetimes.
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classification of the Weyl Tensor in higher dimensions and applications
Classical and Quantum Gravity, 2008Co-Authors: A A ColeyAbstract:We review the theory of alignment in Lorentzian geometry and apply it to the algebraic classification of the Weyl Tensor in higher dimensions. This classification reduces to the well-known Petrov classification of the Weyl Tensor in four dimensions. We discuss the algebraic classification of a number of known higher dimensional spacetimes. There are many applications of the Weyl classification scheme, especially when used in conjunction with the higher dimensional frame formalism that has been developed in order to generalize the four-dimensional Newman–Penrose formalism. For example, we discuss higher dimensional generalizations of the Goldberg–Sachs theorem and the peeling theorem. We also discuss the higher dimensional Lorentzian spacetimes with vanishing scalar curvature invariants and constant scalar curvature invariants, which are of interest since they are solutions of supergravity theory.
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classification of the Weyl Tensor in higher dimensions and applications
arXiv: General Relativity and Quantum Cosmology, 2007Co-Authors: A A ColeyAbstract:We review the theory of alignment in Lorentzian geometry and apply it to the algebraic classification of the Weyl Tensor in higher dimensions. This classification reduces to the the well-known Petrov classification of the Weyl Tensor in four dimensions. We discuss the algebraic classification of a number of known higher dimensional spacetimes. There are many applications of the Weyl classification scheme, especially in conjunction with the higher dimensional frame formalism that has been developed in order to generalize the four dimensional Newman--Penrose formalism. For example, we discuss higher dimensional generalizations of the Goldberg-Sachs theorem and the Peeling theorem. We also discuss the higher dimensional Lorentzian spacetimes with vanishing scalar curvature invariants and constant scalar curvature invariants, which are of interest since they are solutions of supergravity theory.
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classification of the Weyl Tensor in higher dimensions
arXiv: General Relativity and Quantum Cosmology, 2004Co-Authors: A A Coley, Robert Milson, Vojtech Pravda, A PravdovaAbstract:We discuss the algebraic classification of the Weyl Tensor in higher dimensional Lorentzian manifolds. This is done by characterizing algebraically special Weyl Tensors by means of the existence of aligned null vectors of various orders of alignment. Further classification is obtained by specifying the alignment type and utilizing the notion of reducibility. For a complete classification it is then necessary to count aligned directions, the dimension of the alignment variety, and the multiplicity of principal directions. The present classification reduces to the classical Petrov classification in four dimensions. Some applications are briefly discussed.
