scholarly journals Gravitational Lensing

1992 ◽  
Vol 9 ◽  
pp. 3-32 ◽  
Author(s):  
Sjur Refsdal ◽  
Jean Surdej
Keyword(s):  
Gravitational Lensing ◽  
Gravitational Lens ◽  
Medium Size ◽  
Gravitational Lenses ◽  
Optical Lens ◽  
Basic Principles ◽  
History Of ◽  
Photometric Monitoring ◽  
A Site ◽  
Near Future

AbstractAtmospheric lensing effects deform our view of distant objects; similarly, without any doubt, gravitational lensing perturbs our view of the distant Universe and affects our physical understanding of various classes of extragalactic objects. We summarize here part of the theoretical and observational evidences supporting these claims.After briefly reviewing the history of gravitational lenses, we recall the basic principles underlying the formation of gravitationally lensed images of distant cosmic sources. We describe a simple optical lens experiment, which was actually shown during the oral discourse, and which accounts for all types of presently known gravitational lens systems.The various optical and radio searches for new gravitational lens systems that are being carried out at major observatories are reviewed. State-of-the-art observations of selected gravitational lens systems, obtained with highly performing ground-based telescopes, are then presented. These include several examples of multiply imaged QSO images, radio rings and giant luminous arcs.Through the modeling of these enigmatic objects, we show how it is possible to weigh the mass of distant lensing galaxies as well as to probe the distribution of luminous and dark matter in the Universe. Among the astrophysical and cosmological interests of observing and studying gravitational lenses, we also discuss the possibility of deriving the value of the Hubble parameter Ho from the measurement of a time delay, and how to determine the size and structure of distant quasars via the observational study of micro-lensing effects.At the end of this paper, we conclude on how to possibly achieve major astro-physical and cosmological goals in the near future by dedicating, on a site with good atmospheric seeing conditions, a medium size (2-3 m) telescope to the photometric monitoring of the multiple images of known and suspected gravitational lens systems.

GRAVITATIONAL LENS AMPLIFICATION OF GRAVITATIONAL RADIATION

2002 ◽  
Vol 11 (07) ◽  
pp. 1067-1074 ◽  
Author(s):  
ALEXANDER F. ZAKHAROV ◽  
YURI V. BARYSHEV
Keyword(s):  
Gravitational Wave ◽  
Gravitational Lensing ◽  
Gravitational Radiation ◽  
Gravitational Lens ◽  
Wave Form ◽  
Gravitational Lenses ◽  
Approximation Model ◽  
Radiation Sources ◽  
Wave Space ◽  
Stellar Masses

In a recent paper by Wang, Turner and Stebbins (1996) an influence of gravitational lensing on increasing an estimated rate of gravitational radiation sources was considered. We show that the authors used the geometrical optics approximation model for gravitational lensing and thus they gave overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We show also that if we would use a more correct model of gravitational lensing, one could conclude that more strong influence on increasing rate of estimated events of gravitational radiation for advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as Wang et al. concluced. Moreover, binary gravitational lenses could give essential distortion of gravitational wave form template, especially gravitational wave template of periodic sources and the effect could be significant for templates of quasi-periodic sources which could be detected by a future gravitational wave space detector like LISA.

scholarly journals A simple simulation technique for gravitational lenses

2011 ◽  
Vol 20 (2) ◽  
pp. 183-189
Author(s):  
CRISTIAN EDUARD RUSU ◽  
◽  
BETRIA SILVANA ROSSA ◽  
Keyword(s):  
Present Article ◽  
Gravitational Lensing ◽  
Weak Field ◽  
Simulation Technique ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Direct Simulation ◽  
Single Plane ◽  
Advantages And Disadvantages ◽  
Simple Simulation

The present article discusses the simulation of Gravitational Lensing with an algorithm developed in C++ and using the EasyBMP library. The algorithm numerically solves the general gravitational lens equation in the astrophysically significant weak field case, for any single-plane lens configuration. Examples of execution are considered, and a discussion is carried out on the advantages and disadvantages of the direct simulation technique employed.

scholarly journals A Dedicated Quasar Monitoring Telescope

1996 ◽  
Vol 168 ◽  
pp. 527-528
Author(s):  
U. Borgeest ◽  
K.-J. Schramm ◽  
J. Von Linde
Keyword(s):  
Gravitational Lens ◽  
Optical Photometry ◽  
Non Profit ◽  
Intelligent Software ◽  
Data Points ◽  
Weather Control ◽  
5 Ghz ◽  
A Site ◽  
Near Future ◽  
First Time

Under the auspices of Sjur Refsdal, 25 astrophysicists and engineers from Germany and Scandinavia have founded a non-profit association, aiming at the use of an intelligent telescope for quasar monitoring in the optical (Borgeest et al. 1993). Beyond a better understanding of the physics in quasars, the scientific goals are determining the cosmic distance scale at large redshifts and constraining the nature of Dark Matter, both using the gravitational lens effect. Thus, targets of special interest are the multiply lensed quasars and some well-known violently variable blazars. The optical photometry will in part be carried out simultaneously to observations with, e.g., ISO, ROSAT, CGRO and various radio telescopes. For the first time, a complete quasar sample will be monitored continuously, namely a sub-sample of the all-sky 1 Jy catalogue (5 GHz). Since we will collect about 106photometric data points during the programme, Megaphot has been chosen as name for the association. Members from Hamburg and Bochum intend to test the 1.5 m Hexapod Telescope (HPT) astronomically in the very near future. The HPT hardware was developed and built byVertex Antennentechnik, Duisburgtogether with theRuhr-Universität, BochumandCarl Zeiss, Jena;the intelligent software and weather control requires still some work. When working well, the system will be placed at a site with excellent astronomical conditions. After a few years of exclusive quasar monitoring, it will be used as a German photometry telescope.

scholarly journals A VLA Gravitational Lens Survey

1987 ◽  
Vol 124 ◽  
pp. 747-750
Author(s):  
J. N. Hewitt ◽  
E. L. Turner ◽  
B. F. Burke ◽  
C. R. Lawrence ◽  
C. L. Bennett ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Field ◽  
Gravitational Lensing ◽  
Critical Density ◽  
Selection Effect ◽  
Compact Objects ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Number Density ◽  
Luminous Objects

Gravitational lens surveys are of cosmological interest because they provide a way to measure the gravitational field of both luminous and dark matter. Many of the other methods used to detect the presence of dark matter, such as studies of galaxy rotation curves and cluster dynamics, require that there be luminous objects in the gravitational field that act as tracers of the mass. This may introduce a selection effect. In constrast, in studies of gravitational lenses, the beacon we observe can be far (at distances of order one thousand Mpc) from the gravitational field. In this paper we describe a VLA survey designed to detect gravitational lensing on sub-arc second and arc second scales. We also present a preliminary result of the radio data: we find that the density of matter in the form of a uniform, comoving number density of 1011 to 1012M⊙ compact objects, luminous or dark, must be substantially less than the critical density.

scholarly journals Cosmological Applications of Gravitational Lensing

1996 ◽  
Vol 168 ◽  
pp. 209-217
Author(s):  
Peter Schneider
Keyword(s):  
Gravitational Lensing ◽  
High Redshift ◽  
Cosmological Parameters ◽  
Gravitational Lens ◽  
Mass Determination ◽  
Gravitational Lenses ◽  
Distant Object ◽  
The Many ◽  
The Universe

It was recognized very early that the gravitational lens effect can be used as an efficient cosmological tool. Of the many researchers who foresaw the use of lensing, F. Zwicky and S. Refsdal should be explicitly mentioned. The perhaps most accurate predictions and foresights by these two authors are as follows: Zwicky estimated the probability that a distant object is multiply imaged to be about 1/400, and thus that the observation of this effect is “a certainty” [73] – his value, which was obtained by a very crude reasoning, is in fact very close to current estimates of the lensing probability of high-redshift QSOs. He predicted that the magnification caused by gravitational light deflection will allow a “deeper look” into the universe –in fact, the spectroscopy of very faint galaxies which are imaged into giant luminous arcs have yielded spectral information which would be very difficult to obtain without these ‘natural telescopes’. And third, Zwicky saw that gravitational lenses may be used to determine the mass of distant extragalactic objects[72] – in fact, the mass determination of clusters masses from giant luminous arcs is as least as accurate as other methods, but does not rely on special assumptions (like spherical symmetry, virial or thermal equilibrium) inherent in other methods, and the determination of the mass within the inner 0.9 arcseconds of the lensing galaxy in the quadruple QSO 2237+0305 to within 2% [52] is the most accurate extragalactic mass determination known. Refsdal predicted the use of gravitational lenses for determining cosmological parameters and for testing cosmological theories [48][49] – we shall return to these issues below.

scholarly journals The Hubble Constant from (CLASS) Gravitational Lenses

2001 ◽  
Vol 18 (2) ◽  
pp. 179-181 ◽  
Author(s):  
L. V. E. Koopmans ◽  
The CLASS Collaboration
Keyword(s):  
Time Delays ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Monitoring Programs ◽  
Systematic Uncertainties ◽  
Sky Survey ◽  
Image Pairs ◽  
Near Future

AbstractOne of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of time delays between image pairs. The survey is now near completion and at least 18 GL systems have been found. Here, I will discuss our efforts to measure time delays from several of these systems with the ultimate aim of constraining the Hubble Constant (H0). Thus far three CLASS GL systems (B0218+357, B1600+434 and B1608+656) have yielded measurements of time delays, from which values of H0 ≈ 60–70 km s−1 Mpc−1 have been estimated. Although most GL systems give similar values of H0, statistical and systematic uncertainties are still considerable. To reduce these uncertainties, I will mention two monitoring programs that we are undertaking to (re)measure time delays in 14 CLASS GL systems and address several important issues for the near future.

Chemical and Electrochemical Heteroepitaxial Growth of Chalcogenide Semiconductors from Solutions

1996 ◽  
Vol 451 ◽  
Author(s):  
D. Lincot ◽  
M. J. Furlong ◽  
M. Froment ◽  
R. Cortes ◽  
M. C. Bernard
Keyword(s):  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
Basic Principles ◽  
Lattice Match ◽  
X Ray ◽  
Chalcogenide Semiconductors ◽  
Influence Of Temperature On ◽  
Deposition Processes ◽  
A Site ◽  
Site Selective

ABSTRACTChalcogenide semiconductors have been deposited epitaxially from aqueous solutions either chemically or electrochemically at growth rates of up to 0.7 μmhr−1. After recalling the basic principles of these deposition processes, results are presented concerning chemically deposited CdS on InP, GaP and CuInSe2 substrates, electrodeposited CdTe on InP, and CdSAnP heterostructures. Characterisation of these structures by RHEED, TEM, HRTEM, and glazing angle X ray diffraction allows to analyse the effects of substrate orientation, polarity, lattice match plus the influence of temperature on epitaxial growth. These results are discussed in terms of self organisation and a site selective growth mechanisms due to the free enegy of formation of each compound.

On the Publishing Infrastructure of the University and its Construction Principles

2010 ◽  
pp. 121-126
Author(s):  
Tatyana F. Berestova ◽  
Vera R. Abramovskih
Keyword(s):  
Research Library ◽  
Basic Principles ◽  
History Of ◽  
Publishing Infrastructure ◽  
Distribution Sector ◽  
The University

The basic principles of publishing activities in universities and their interrelation, all stages of redaction, the problems each of them, and ways to solve them. The activities of the distribution sector of publishing in the structure of the Research Library of Chelyabinsk State Academy of Culture and Arts and the history of its creation are described.

La valorisation des prestations non-bois: particularités genevoises (essai) | Commercialization of non-wood forest services: the case of Geneva (essay)

2009 ◽  
Vol 160 (8) ◽  
pp. 232-234
Author(s):  
Patrik Fouvy
Keyword(s):  
Forest Regeneration ◽  
Biological Diversity ◽  
The State ◽  
Forest Land ◽  
Private Forests ◽  
The Public ◽  
Public Body ◽  
Provision Of Services ◽  
History Of ◽  
Near Future

The history of the forests in canton Geneva, having led to these being disconnected from productive functions, provides a symptomatic demonstration that the services provided by the forest eco-system are common goods. Having no hope of financial returns in the near future and faced with increasing social demands, the state has invested in the purchase of forest land, financed projects for forest regeneration and improvement of biological diversity and developed infrastructures for visitors. In doing this the state as a public body takes on the provision of services in the public interest. But the further funding for this and for expenses for the private forests, which must be taken into account, are not secured for the future.

The Reformation of Prophecy

2018 ◽  
Author(s):  
G. Sujin Pak
Keyword(s):  
Old Testament ◽  
Word Of God ◽  
Priesthood Of All Believers ◽  
Beliefs And Practices ◽  
The People ◽  
The Reformation ◽  
History Of ◽  
A Site ◽  
Developmental Analysis ◽  
Sacred History

The Reformation of Prophecy presents and supports the case for viewing the prophet and biblical prophecy as a powerful lens by which to illuminate many aspects of the reforming work of the Protestant reformers in the sixteenth and seventeenth centuries. It provides a chronological and developmental analysis of the significance of the prophet and biblical prophecy across leading Protestant reformers in articulating a theology of the priesthood of all believers, a biblical model of the pastoral office, a biblical vision of the reform of worship, and biblical processes for discerning right interpretation of Scripture. Through the tool of the prophet and biblical prophecy, the reformers framed their work under, within, and in support of the authority of Scripture—for the true prophet speaks the Word of God alone and calls the people, their worship and their beliefs and practices, back to the Word of God. The book also demonstrates how interpretations and understandings of the prophet and biblical prophecy contributed to the formation and consolidation of distinctive confessional identities, especially around differences in their visions of sacred history, Christological exegesis of Old Testament prophecy, and interpretation of Old Testament metaphors. This book illuminates the significant shifts in the history of Protestant reformers’ engagement with the prophet and biblical prophecy—shifts from these serving as a tool to advance the priesthood of all believers to a tool to clarify and buttress clerical identity and authority to a site of polemical-confessional exchange concerning right interpretations of Scripture.

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