共查询到20条相似文献,搜索用时 15 毫秒
1.
To recognize gravitational wave lensing events and being able to differentiate between similar lens models will be of crucial importance once one will be observing several lensing events of gravitational waves per year. In this work, the lensing of gravitational waves is studied in the context of LISA sources and wave-optics regime. While different papers before the studied microlensing effects enhanced by simultaneous strong lensing, the focus is on frequency (time) dependent phase effects produced by one lens that will be visible with only one lensed signal. It is shows how, in the interference regime (i.e., when interference patterns are present in the lensed image), one is able to i) distinguish a lensed waveform from an unlensed one, and ii) differentiate between different lens models. In pure wave-optics, on the other hand, the feasibility of the study depends on the signal-to-noise ratio of the signal and/or the amplitude of the lensing effect. To achieve these goals, the phase of the amplification factor of the different lens models and its effect on the unlensed waveform is studied, and the signal-to-noise calculation to provide some quantitative examples is exploited. 相似文献
2.
If the dark matter consists of primordial black holes (PBHs), we show that gravitational lensing of stars being monitored by NASA's Kepler search for extrasolar planets can cause significant numbers of detectable microlensing events. A search through the roughly 150,000 light curves would result in large numbers of detectable events for PBHs in the mass range 5×10(-10) M(⊙) to 10(-4) M(⊙). Nondetection of these events would close almost 2 orders of magnitude of the mass window for PBH dark matter. The microlensing rate is higher than previously noticed due to a combination of the exceptional photometric precision of the Kepler mission and the increase in cross section due to the large angular sizes of the relatively nearby Kepler field stars. We also present a new formalism for calculating optical depth and microlensing rates in the presence of large finite-source effects. 相似文献
3.
Gravitational waves can act as gravitationallenses and create multiple images of a light source.This situation is much more interesting thansingle-image lensing because of the associatedhigh-amplification events that may lead to the indirect detectionof gravitational waves. It is proposed to observe theeffect due to gravitational waves generated in supernovaexplosions. 相似文献
4.
Valerio Bozza 《General Relativity and Gravitation》2010,42(9):2269-2300
We review the theoretical aspects of gravitational lensing by black holes, and discuss the perspectives for realistic observations.
We will first treat lensing by spherically symmetric black holes, in which the formation of infinite sequences of higher order
images emerges in the clearest way. We will then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the perspectives for observations of black hole
lensing, from the detection of secondary images of stellar sources and spots on the accretion disk to the interpretation of
iron K-lines and direct imaging of the shadow of the black hole. 相似文献
5.
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. 相似文献
6.
For ultra compact objects, light rings and fundamental photon orbits (FPOs) play a pivotal role in the theoretical analysis of strong gravitational lensing effects, and of BH shadows in particular. In this short review, specific models are considered to illustrate how FPOs can be useful in order to understand some non-trivial gravitational lensing effects. This paper aims at briefly overviewing the theoretical foundations of these effects, touching also some of the related phenomenology, both in general relativity and alternative theories of gravity, hopefully providing some intuition and new insights for the underlying physics, which might be critical when testing the Kerr black hole hypothesis. 相似文献
7.
The mathematical theory of gravitational lensing has revealed many generic and global properties. Beginning with multiple
imaging, we review Morse-theoretic image counting formulas and lower bound results, and complex-algebraic upper bounds in
the case of single and multiple lens planes. We discuss recent advances in the mathematics of stochastic lensing, discussing
a general formula for the global expected number of minimum lensed images as well as asymptotic formulas for the probability
densities of the microlensing random time delay functions, random lensing maps, and random shear, and an asymptotic expression
for the global expected number of micro-minima. Multiple imaging in optical geometry and a spacetime setting are treated.
We review global magnification relation results for model-dependent scenarios and cover recent developments on universal local
magnification relations for higher order caustics. 相似文献
8.
Riemer-Sørensen S Zioutas K Hansen SH Pedersen K Dahle H Liolios A 《Physical review letters》2007,99(13):131301
We constrain the lifetime of radiatively decaying dark matter in clusters of galaxies inspired by generic Kaluza-Klein axions, which have been invoked as a possible explanation for the solar coronal x-ray emission. These particles can be produced inside stars and remain confined by the gravitational potential of clusters. By analyzing x-ray observations of merging clusters, where gravitational lensing observations have identified massive, baryon poor structures, we derive the first cosmological lifetime constraint on this kind of particles of tau > or = 10(23) sec. 相似文献
9.
Because gamma-ray bursts(GRBs)trace the high-z universe,there is an appreciable probability for a GRB to be gravitational lensed by galaxies in the universe.Herein we consider the gravitational lensing effect of GRBs contributed by the dark matter halos in galaxies.Assuming that all halos have the singular isothermal sphere(SIS)mass profile in the mass range 1010h?1M?M2×1013h?1M?and all GRB samples follow the intrinsic redshift distribution and luminosity function derived from the Swift LGRBs sample,we calculated the gravitational lensing probability in BATSE,Swift/BAT and Fermi/GBM GRBs,respectively.With an derived probability result in BATSE GRBs,we searched for lensed GRB pairs in the BATSE5B GRB Spectral catalog.The search did not find any convincing gravitationally lensed events.We discuss our result and future observations for GRB lensing observation. 相似文献
10.
Juan Deng 《International Journal of Theoretical Physics》2012,51(5):1632-1639
The principal focus of this paper is to study the strong field gravitational lensing in a magnetic charged Reissner-Nordstr?m
black hole based on the method of cosmic string. We obtain the new coefficients including the tension of the cosmic strings,
the strong field deflection limit coefficients, the deflection angle and the magnification, and obtain the relationship between
the cosmic string parameter and the new coefficients. The result shows that the cosmic strings have some important effect
on the gravitational lensing in a black hole when they pierce it. 相似文献
11.
M. Lubini C. Tortora J. Näf Ph. Jetzer S. Capozziello 《The European Physical Journal C - Particles and Fields》2011,71(12):1834
For a general class of analytic f(R)-gravity theories, we discuss the weak field limit in view of gravitational lensing. Though an additional Yukawa term in
the gravitational potential modifies dynamics with respect to the standard Newtonian limit of General Relativity, the motion
of massless particles results unaffected thanks to suitable cancellations in the post-Newtonian limit. Thus, all the lensing
observables are equal to the ones known from General Relativity. Since f(R)-gravity is claimed, among other things, to be a possible solution to overcome for the need of dark matter in virialized
systems, we discuss the impact of our results on the dynamical and gravitational lensing analyses. In this framework, dynamics
could, in principle, be able to reproduce the astrophysical observations without recurring to dark matter, but in the case
of gravitational lensing we find that dark matter is an unavoidable ingredient. Another important implication is that gravitational
lensing, in the post-Newtonian limit, is not able to constrain these extended theories, since their predictions do not differ
from General Relativity. 相似文献
12.
M. Arnaud Varvella M. C. Angonin Ph. Tourrenc 《General Relativity and Gravitation》2004,36(5):983-999
This article deals with the gravitational lensing (GL) of gravitational waves (GW). We compute the increase in the number of detected GW events due to GL. First, we check that geometrical optics is valid for the GW frequency range on which Earth-based detectors are sensitive, and that this is also partially true for what concerns the future space-based interferometer LISA. To infer this result, both the diffraction parameter and a cut-off frequency are computed. Then, the variation in the number of GW signals is estimated in the general case, and applied to some lens models: point mass lens and singular isothermal sphere (SIS profile). An estimation of the magnification factor has also been done for the softened isothermal sphere and for the King profile. The results appear to be strongly model-dependent, but in all cases the increase in the number of detected GW signals is negligible. The use of time delays among images is also investigated. 相似文献
13.
Weak gravitational lensing has several important effects on the cosmic microwave background (CMB): it changes the CMB power spectra, induces non-Gaussianities, and generates a B-mode polarization signal that is an important source of confusion for the signal from primordial gravitational waves. The lensing signal can also be used to help constrain cosmological parameters and lensing mass distributions. We review the origin and calculation of these effects. Topics include: lensing in General Relativity, the lensing potential, lensed temperature and polarization power spectra, implications for constraining inflation, non-Gaussian structure, reconstruction of the lensing potential, delensing, sky curvature corrections, simulations, cosmological parameter estimation, cluster mass reconstruction, and moving lenses/dipole lensing. 相似文献
14.
Cosmic strings are linear structures of cosmological scales whose search has been actively conducted in recent years. Progress
in constructing theoretical models and investigating the properties of cosmic strings and a significant growth of observational
resources provide extensive possibilities for the search of such objects by several independent observational methods. These
methods include searching for the events of gravitational lensing of distant background sources by strings and searching for
the distinctive cosmic micro-wave background anisotropy structures induced by strings. We discuss these techniques and propose
the methods of searching for strings oriented toward the latest spacecraft, including the Planck project. 相似文献
15.
Timothy A. McKay 《Contemporary Physics》2013,54(6):451-460
Light propagating in an inhomogeneous medium does not travel in straight lines. Light rays wander; they are focused, magnified and dispersed as they travel through an inhomogeneous medium. Such deflections are familiar to physicists. They are the stuff of optics. On cosmic scales light is 'deflected' in a more profound way, tracing inhomogeneities in the underlying space-time. The meandering of light rays as they propagate through the Universe encodes unique information about variations in the space-time metric. General relativity tells us these variations are impressed on the metric by inhomogeneities in the matter distribution. As a result, this 'gravitational lensing' provides information about the distribution of mass in the Universe. In this work we review briefly the main features of gravitational lensing, with an emphasis on observable effects. Remarkable progress has been made in lensing observations since 1990. We discuss some aspects of this rapid development, commenting especially on astrophysical topics where lensing studies have had a major impact. We suggest that gravitational lensing is now a standard part of the astrophysical toolkit, akin in some ways to photometry. We conclude with a discussion of areas in which lensing studies will have a strong impact in years to come, and comment on technical requirements for these future studies. 相似文献
16.
To test modified Newtonian dynamics (MOND) on galactic scales, we study six strong gravitational lensing early-type galaxies from the CASTLES sample. Comparing the total mass (from lensing) with the stellar mass content (from a comparison of photometry and stellar population synthesis), we conclude that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain the excess of matter in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MOND scale of approximately 10(-10) m/s(2). This is a serious challenge to MOND unless lensing is qualitatively different [possibly to be developed within a covariant, such as Tensor-Vector-Scalar (TeVeS), theory]. 相似文献
17.
Volker Perlick 《Communications in Mathematical Physics》2001,220(2):403-428
In a general-relativistic spacetime (Lorentzian manifold), gravitational lensing can be characterized by a lens map, in analogy
to the lens map of the quasi-Newtonian approximation formalism. The lens map is defined on the celestial sphere of the observer
(or on part of it) and it takes values in a two-dimensional manifold representing a two-parameter family of worldlines. In
this article we use methods from differential topology to characterize global properties of the lens map. Among other things,
we use the mapping degree (also known as Brouwer degree) of the lens map as a tool for characterizing the number of images
in gravitational lensing situations. Finally, we illustrate the general results with gravitational lensing (a) by a static
string, (b) by a spherically symmetric body, (c) in asymptotically simple and empty spacetimes, and (d) in weakly perturbed
Robertson–Walker spacetimes.
Received: 16 October 2000 / Accepted: 18 January 2001 相似文献
18.
Matteo Luca Ruggiero 《General Relativity and Gravitation》2009,41(7):1497-1509
We investigate gravitational lensing in the Palatini approach to the f (R) extended theories of gravity. Starting from an exact solution of the f (R) field equations, which corresponds to the Schwarzschild–de Sitter metric and, on the basis of recent studies on this metric,
we focus on some lensing observables, in order to evaluate the effects of the nonlinearity of the gravity Lagrangian. We give
estimates for some astrophysical events, and show that these effects are tiny for galactic lenses, but become interesting
for extragalactic ones. 相似文献
19.
Alexander Zakharov 《General Relativity and Gravitation》2010,42(9):2301-2322
Many exotic astronomical objects have been introduced. Usually the objects have masses, therefore they may act as gravitational
lenses. We briefly discuss gravitational lensing with cosmic strings. As is well-known, dark matter is one of the most important
components of the Universe. Recent computer simulations indicate that dark matter may form clumps. We review gravitational
lensing (including microlensing) for the clumps. 相似文献
20.
Inflationary gravitational waves (GW) contribute to the curl component in the polarization of the cosmic microwave background (CMB). Cosmic shear--gravitational lensing of the CMB--converts a fraction of the dominant gradient polarization to the curl component. Higher-order correlations can be used to map the cosmic shear and subtract this contribution to the curl. Arcminute resolution will be required to pursue GW amplitudes smaller than those accessible by the Planck surveyor mission. The blurring by lensing of small-scale CMB power leads with this reconstruction technique to a minimum detectable GW amplitude corresponding to an inflation energy near 10(15) GeV. 相似文献