New Limits on a Cosmological Constant from Statistics of Gravitational Lensing

1999 ◽  
Vol 510 (1) ◽  
pp. 42-53 ◽  
Author(s):  
Masashi Chiba ◽  
Yuzuru Yoshii
Keyword(s):  
Cosmological Constant ◽  
Gravitational Lensing

scholarly journals Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

Open Physics ◽  
2007 ◽  
Vol 5 (4) ◽  
Author(s):  
Pavel Bakala ◽  
Petr Čermák ◽  
Stanislav Hledík ◽  
Zdeněk Stuchlík ◽  
Kamila Truparová
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Gravitational Lensing ◽  
High Performance ◽  
Computer Code ◽  
De Sitter ◽  
Simulation Code ◽  
Black Hole Spacetimes ◽  
Optical Projection ◽  
Free Falling

AbstractWe have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.

scholarly journals Deflection of light around a rotating BTZ black hole

2020 ◽  
Vol 35 (39) ◽  
pp. 2050323
Author(s):  
Shubham Kala ◽  
Hemwati Nandan ◽  
Prateek Sharma
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Test Particle ◽  
Gravitational Lensing ◽  
Critical Parameters ◽  
Btz Black Hole ◽  
Bending Angle ◽  
Retrograde Motion ◽  
Test Particles ◽  
Dimensional Gravity

We present a detailed study of gravitational lensing around a rotating Bañados–Teitelboim–Zanelli (BTZ) black hole in (2 + 1)-dimensional gravity. The study of orbits for massless test particle around this BH spacetime is performed to describe the nature of cosmological constant in lower dimensions. We study the effect of cosmological constant on the photon orbit in view of other critical parameters. The bending angle of light is studied in view of different values of cosmological constant for direct and retrograde motion of test particles. It is being observed that the bending angle slightly decreases as the value of cosmological constant increases in the negative region.

CONSTRAINT ON THE COSMOLOGICAL CONSTANT FROM GRAVITATIONAL LENSING IN AN EVOLUTIONARY MODEL OF GALAXIES

1998 ◽  
Vol 13 (24) ◽  
pp. 4227-4236 ◽  
Author(s):  
DEEPAK JAIN ◽  
N. PANCHAPAKESAN ◽  
S. MAHAJAN ◽  
V. B. BHATIA
Keyword(s):  
Cosmological Constant ◽  
Galaxy Evolution ◽  
Optical Depth ◽  
Gravitational Lensing ◽  
Statistical Study ◽  
Evolutionary Model ◽  
Building Blocks ◽  
Lens Model ◽  
Gravitational Lenses ◽  
Luminosity Evolution

We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Ω0+λ0=1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low-density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the lens distribution may be used best for this purpose without depending much on the lens model. We calculate the optical depth (probability of a beam encountering a lens event) for a source in a new picture of galaxy evolution based on number evolution in addition to pure luminosity evolution. It seem that present-day galaxies result from the merging of a large number of building blocks. We have tried to put a limit on the cosmological constant in this new picture of galaxy evolution. This evolutionary model of galaxies permits a larger value of the cosmological constant.

scholarly journals GRAVITATIONAL LENSING STATISTICS AND CONSTRAINTS ON THE COSMOLOGICAL CONSTANT REVISITED

2000 ◽  
Vol 15 (05) ◽  
pp. 697-723 ◽  
Author(s):  
YU-CHUNG N. CHENG ◽  
LAWRENCE M. KRAUSS
Keyword(s):  
Cosmological Constant ◽  
Gravitational Lensing ◽  
Velocity Dispersion ◽  
A Value ◽  
Galaxy Distribution ◽  
Systematic Uncertainties ◽  
Luminosity Functions ◽  
Likelihood Analysis ◽  
The Galaxy ◽  
Velocity Dispersions

We re-analyze constraints on the cosmological constant that can be obtained by examining the statistics of strong gravitational lensing of distant quasars by intervening galaxies, focusing on uncertainties in galaxy models (including velocity dispersion, luminosity functions, core radii and magnification bias effects) and on the parameters of the galaxy distribution and luminosity functions. In the process we derive new results on magnification biasing for galaxy lenses with nonzero core radii, and on how to infer the proper velocity dispersions appropriate for use in lensing statistics. We argue that the existing data do not disfavor a large cosmological constant. In fact, for a set of reasonable parameter choices, using the results of five optical quasar lensing surveys we find that a maximum likelihood analysis favors a value of Ω0 in the range ≈ 0.25–0.55 in a flat universe. An open cosmology is not favored by the same statistical analysis. Systematic uncertainties are likely to be dominant, however, as these results are sensitive to uncertainties in our understanding of galaxy luminosity functions, and dark matter velocity dispersions, as well as the choice of lensing survey, and to a lesser extent the existence of core radii. Further observational work will be required before it is possible to definitively distinguish between cosmological models on the basis of gravitational lensing statistics.

THE CASE FOR A POSITIVE COSMOLOGICAL Λ-TERM

2000 ◽  
Vol 09 (04) ◽  
pp. 373-443 ◽  
Author(s):  
VARUN SAHNI ◽  
ALEXEI STAROBINSKY
Keyword(s):  
Cosmological Constant ◽  
Gravitational Lensing ◽  
High Redshift ◽  
Scalar Fields ◽  
Accelerating Universe ◽  
Microwave Background ◽  
Present Epoch ◽  
Polarization Effects ◽  
Age Of The Universe ◽  
The Universe

Recent observations of Type 1a supernovae indicating an accelerating universe have once more drawn attention to the possible existence, at the present epoch, of a small positive Λ-term (cosmological constant). In this paper we review both observational and theoretical aspects of a small cosmological Λ-term. We discuss the current observational situation focusing on cosmological tests of Λ including the age of the universe, high redshift supernovae, gravitational lensing, galaxy clustering and the cosmic microwave background. We also review the theoretical debate surrounding Λ: the generation of Λ in models with spontaneous symmetry breaking and through quantum vacuum polarization effects — mechanisms which are known to give rise to a large value of Λ hence leading to the "cosmological constant problem." More recent attempts to generate a small cosmological constant at the present epoch using either field theoretic techniques, or by modelling a dynamical Λ-term by scalar fields are also extensively discussed. Anthropic arguments favouring a small Λ-term are briefly reviewed. A comprehensive bibliography of recent work on Λ is provided.

Gravitational Lensing as Probe of Large Scale Structure of the Universe

2005 ◽  
Vol 201 ◽  
pp. 437-438
Author(s):  
V. B. Bhatia ◽  
D. Jain ◽  
S. Mahajan ◽  
N. Panchapakesan
Keyword(s):  
Cosmological Constant ◽  
Galaxy Evolution ◽  
Gravitational Lensing ◽  
Large Scale ◽  
Gamma Ray ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Red Shift ◽  
Sources Of Uncertainty ◽  
The Universe

We apply gravitational lensing statistics to: (1) place a limit on the cosmological constant (ΩΛ); (2) place a limit on the average red-shift (< z >) of gamma-ray bursters (GRBs); (3) investigate models of galaxy evolution to see how compatible these models are with lensing statistics. We also point out the sources of uncertainty in lensing statistics, leading to uncertainty in the results.

Realistic Galaxy Models for Lensing Statistics

2005 ◽  
Vol 201 ◽  
pp. 292-295
Author(s):  
David. Rusin ◽  
Max. Tegmark
Keyword(s):  
Cosmological Constant ◽  
Optical Depth ◽  
Gravitational Lensing ◽  
Significant Progress ◽  
Data Set ◽  
Cosmological Constraints ◽  
Lens Galaxies

The gravitational lensing rate in a well-defined sample of sources can place strong bounds on the cosmological constant, but only if the lensing optical depth is robustly calculated. Significant progress is likely to be achieved by employing more realistic models to describe the population of lens galaxies. Here we investigate the role of elliptical deflectors in lensing statistics, and their effect on cosmological constraints derived from the JVAS survey. We also evaluate the prospects for constraining the cosmological constant using the much larger CLASS data set.

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