scholarly journals Effects Of Large-Scale Structure Upon The Determination Of Ho From Time Delays

1996 ◽  
Vol 173 ◽  
pp. 91-92
Author(s):  
G.C. Surpi ◽  
D.D. Harari ◽  
J.A. Frieman

We have analyzed the effects of both large-scale inhomogeneities in the mass distribution and cosmological gravitational waves upon the time delay between two images in a gravitational lens system. We have shown that their leading order effect, which could potentially bias the determination of the Hubble parameter, is indistinguishable from a change in the relative angle between the source and the lens axis. Since the absolute angular position of the source is not directly measurable, nor does it enter the relationship between the Hubble parameter and the lens observables, the determination of Ho from gravitational lens time delays follows in the usual way, as if the metric perturbations were absent.

1996 ◽  
Vol 464 ◽  
pp. 54 ◽  
Author(s):  
Gabriela C. Surpi ◽  
Diego D. Harari ◽  
Joshua A. Frieman

2006 ◽  
Vol 447 (3) ◽  
pp. 905-913 ◽  
Author(s):  
V. Vakulik ◽  
R. Schild ◽  
V. Dudinov ◽  
S. Nuritdinov ◽  
V. Tsvetkova ◽  
...  

1988 ◽  
Vol 129 ◽  
pp. 191-199
Author(s):  
Edwin L. Turner

Four specific and particularly powerful types of possible VLBI lens studies are discussed. First, comparison of mas scale structure in putative pairs of images separated by arc seconds can provide a powerful additional test of the lens hypothesis in specific candidate systems. Second, VLBI searches for lens systems with image separations too small for resolution by optical or VLA searches will limit (or even determine!) the cosmological density of condensed objects with individual masses ∼ 106M⊙. Third, study of multiply imaged superluminal expansion events will allow a determination of the light travel time delay between different images in a lens system, a quantity which is quite difficult to measure by other means but which would allow profound cosmological tests. Fourth, VLBI data can be used to determine relative image parities and even the full magnification matrix of various images in a lens system, thus providing powerful additional constraints on detailed lens models. Finally, the speculative possibility of detecting Galactic stellar lensing events using VLBI techniques is discussed.


2020 ◽  
Author(s):  
Julian Packheiser ◽  
Judith Schmitz ◽  
Gesa Berretz ◽  
David Carey ◽  
Silvia Paracchini ◽  
...  

Human lateral preferences, such as handedness and footedness, have interested researchers for decades due to their pronounced asymmetries at population level. While there are good estimates on the prevalence of handedness in the population, there is, to this, day no large-scale estimation on the prevalence of footedness. Furthermore, the relationship between footedness and handedness still remains elusive. Here, we conducted meta-analyses with four different classification systems for footedness on 145,150 individuals across 164 studies including new data from the ALSPAC cohort. The aims of the study were to determine a reliable point estimate of footedness, to study the association between footedness and handedness, and to investigate moderating factors influencing footedness. We showed that the prevalence of atypical footedness ranges between 12.10% using the most conservative criterion of left-footedness to 23.7% including all left- and mixed-footers as a single non-right category. As many as 60.1% of left-handers were left-footed whereas only 3.2% of right-handers were left-footed. Males were 4.1% more often non-right-footed compared to females. Individuals with psychiatric and neurodevelopmental disorders exhibited a higher prevalence of non-right-footedness. Furthermore, the presence of mixed-footedness was higher in children compared to adults as well as in experienced athletes compared to the general population. Finally, we showed that footedness is only marginally influenced by cultural and social factors, which have been shown to play a crucial role in the determination of handedness. Overall, this study provides new and useful reference data for laterality research. Furthermore, the data suggest that footedness is a valuable phenotype for the study of lateral motor biases, its underlying genetics and neurodevelopment.


2004 ◽  
Vol 220 ◽  
pp. 143-144
Author(s):  
Masamune Oguri

Recent development of the structure formation theory based on the cold dark matter scenario implies that a number of larger separation lensed quasars, for which a confirmed detection has not yet been achieved, will be observed in the ongoing large-scale surveys such as the 2dF survey and SDSS. We show that statistics of such large separation lenses can be a powerful probe of the density profile of dark halos. After we summarize the current status of the lens surveys in the 2dF and SDSS, we focus our discussion on what information can be extracted from these lens surveys. in addition, we also propose statistics of differential time delays between multiple images as an alternative probe of the density profile of dark halos.


2005 ◽  
Vol 201 ◽  
pp. 455-456
Author(s):  
Christopher. Fassnacht ◽  
Emily. Xanthopoulos ◽  
David. Rusin ◽  
Leon. Koopmans

The gravitational lens CLASS B1608+656 is one of the most promising lens systems for the measurement of H0 on cosmological scales. The three independent time delays between the four lensed images have been measured, and the extended lensed optical emission holds the promise for a very well-constrained model. The published time delay measurements are based on the first season of VLA monitoring, in which the background source varied by only 5% in flux density. The small level of variation leads to relatively large uncertainties in the determination of the time delays (10-20%). Two more seasons of monitoring have now been completed and the source flux density has changed by ˜25% during that time. We present the results of the continued VLA monitoring and the resulting time-delay analysis. The new data have significantly reduced the uncertainties on the time delays and, hence, reduced the uncertainties on the resulting determination of H0 from this system.


2020 ◽  
Author(s):  
Kamensky IP ◽  
Sudad H Al-Obaidi ◽  
Khalaf FH

As it is well known that, formation porosity and permeability are fundamental rock properties. Porosity is a measure of the storage capacity of the rock and permeability is a measure of rock flow capacity. In this study the relationship of the scale effect with the features and type of the capacitive structure of complex reservoirs is shown. The characteristic conditions for the manifestation of large-scale effects in determining porosity and permeability are analyzed. Also in this work the influence of the scale effect on the representativeness of laboratory determinations of flow- storage capacitance (FSC) properties is shown. The relationship between the values of porosity and permeability with the object of the core study has been established.


2002 ◽  
Vol 33 (1) ◽  
pp. 95-110 ◽  
Author(s):  
A. A. Aleynikov ◽  
V. V. Popovnin ◽  
K. F. Voytkovskiy ◽  
Ye. A. Zolotaryov

The relationship between the thickness of a glacier stream and its surface slope is discussed. Morphometrical features of the glacier surface serve as a basis for estimating the maximum thickness the glacier can attain. A method for indirect calculation of ice thickness is hereby suggested. A detailed large-scale map permits determination of the total glacier volume. The Djankuat Glacier, a representative valley glacier in the Central Caucasus, is used as an example to illustrate the applicability of the proposed calculation scheme. Its probable thickness and volume are estimated on the grounds of photogrammetrical surveys, a topographic map and spatial pattern of ice flow velocity on the surface. Several values of directly measured ice thickness (by various methods such as thermal drilling, radar sounding, gravimetry etc.) verify the calculation results. As a result, ice thickness over the entire glacier area has been mapped. Methodical limitations and accuracy of indirect estimates are also discussed.


2012 ◽  
Vol 8 (S289) ◽  
pp. 331-338
Author(s):  
S. H. Suyu

AbstractThe time delays between the multiple images of a strong gravitational-lens system, together with a model of the lens-mass distribution, provide a one-step determination of the time-delay distance, and thus a measure of cosmological parameters, particularly the Hubble constant, H0. I review the recent advances in measuring time-delay distances, and present the current status of cosmological constraints based on gravitational-lens time delays. In particular, I report the time-delay distance measurements of two gravitational lenses and their implication for cosmology from a recent study by Suyuet al.


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