scholarly journals Constraint on cosmological model with matter creation using complementary astronomical observations

2007 ◽  
Vol 311 (4) ◽  
pp. 407-411 ◽  
Author(s):  
Yuan Qiang ◽  
Tong-Jie Zhang ◽  
Ze-Long Yi
2009 ◽  
Vol 18 (13) ◽  
pp. 2007-2022 ◽  
Author(s):  
SERGIO DEL CAMPO ◽  
J. R. VILLANUEVA

In this paper we study a quintessence cosmological model in which the dark energy component is considered to be the generalized Chaplygin gas and the curvature of the three-geometry is taken into account. Two parameters characterize this sort of fluid: ν and α. We use different astronomical data for restricting these parameters. It is shown that the constraint ν ≲ α agrees well enough with the astronomical observations.


2013 ◽  
Vol 22 ◽  
pp. 593-602 ◽  
Author(s):  
RAJ BALI ◽  
LAXMI POONIA

Bianchi Type VI0 inflationary cosmological model with flat potential in General Relativity, is investigated. To get the deterministic solution in terms of cosmic time t, we assume that σ (shear) is proportional to expansion (θ) where [Formula: see text] Thus [Formula: see text], leads to A = Bn where A and B are metric potentials and n is a constant. We find that spatial volume increases with time. Hence inflationary scenario exists in the model. Since [Formula: see text] in general. Thus the model represents anisotropic universe throughout. However, if [Formula: see text] then the model isotropizes. This result matches with astronomical observations. The model represents decelerating and late time acceleration which matches with recent astronomical observations Riess et al. [29], Perlmutter et al. [30]. The model has Point Type singularity at [Formula: see text] (MacCallum [31]). The rate of Higg’s field (φ) decreases with time.


1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.


1975 ◽  
Vol 26 ◽  
pp. 293-295 ◽  
Author(s):  
I. Zhongolovitch

Considering the future development and general solution of the problem under consideration and also the high precision attainable by astronomical observations, the following procedure may be the most rational approach:1. On the main tectonic plates of the Earth’s crust, powerful movable radio telescopes should be mounted at the same points where standard optical instruments are installed. There should be two stations separated by a distance of about 6 to 8000 kilometers on each plate. Thus, we obtain a fundamental polyhedron embracing the whole Earth with about 10 to 12 apexes, and with its sides represented by VLBI.


2019 ◽  
Vol 2 (1) ◽  
pp. 10402-1-10402-11
Author(s):  
Midori Tanaka ◽  
Takahiko Horiuchi ◽  
Ken’ichi Otani

Abstract A planetarium imitates a starry sky with physical and technical limitations using a dome, projector, and light source. It is widely used for entertainment, and astronomy and physics educations. In our previous study, we investigated the evaluation for faithful reproduction of a star field in a planetarium by performing psychometric experiments with 20 observers for plural projection patterns with different reproduction factors (color, luminance, and size of projected stars). In this study, we investigate the relationship between faithfulness and preference of a star field in a planetarium through a psychometric experiment with 47 observers. The experimental procedure followed the previous study. The rating of faithfulness improved for the projection pattern with a smaller star size. For the preference evaluation, the projection pattern with low luminance significantly lowered the preference rating. The results of the experiment indicate that the preferable star reproduction was different between male and female observers, whereas the faithful star reproduction was not significantly different in the evaluations between male and female observers. The male observers sought a faithful star reproduction as the preferred reproduction. In contrast, the female observers did not feel the faithful star reproduction preferable, and evaluated the more brilliant star reproduction as the preferred reproduction. These results were not dependent on the experience in astronomical observations.


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