424 research outputs found
Influences of Dark Energy and dark matter on Gravitational Time Advancement
The effect of dark matter/energy on gravitational time advancement (negative
effective time delay) has been investigated considering few dark energy/matter
models including cosmological constant. It is found that dark energy gives only
(positive) gravitational time delay irrespective of the position of the
observer whereas pure Schwarzschild geometry leads to gravitational time
advancement when the observer is situated at relatively stronger gravitational
field point in the light trajectory. Consequently, there will be no time
advancement effect at all at radial distances where gravitational field due to
dark energy is stronger than the gravitational field of Schwarzschild geometry.Comment: 7 pages, no figur
Effects of dark energy and flat rotation curve on the gravitational time delay of particle with non-zero mass
The effects of several dark energy models on gravitational time delay of
particles with non-zero mass are investigated and analytical expressions for
the same are obtained at the first order accuracy. Also the expression for
gravitational time delay under the influence of conformal gravity potential
that well describes the flat rotation curve of spiral galaxies is derived. The
findings suggest that i) the conformal gravity description of dark matter
reduces the net time delay in contrast to the effect of normal dark matter and
therefore in principle the models can be discriminated using gravitational time
delay observations and ii)the effect of dark energy/flat rotation curve may be
revealed from high precision measurements of gravitational time delay of
particles involving megaparsec and beyond distance-scale.Comment: 10 page
Effect of edible coatings for enhancing shelf-life and quality in Ber (Zizyphus mauritiana Lamk.) fruits
An experiment was conducted to study the effect of post-harvest application of different edible coatings like Chitosan (0.5%, 1.0%, 2.0%), Guar gum (1%, 1.5%, 2%), Gum tragacanth (1.0%, 1.5%, 2.0%) on shelf life and quality of cv. BAU ber. Fruits of uniform size were harvested at physiological maturity and treated with various edible coatings. Observations were recorded at intervals of 4 days from storage on physiological loss in weight, fruit length, breadth, colour, TSS, total sugar, reducing sugar,acidity, and ascorbic acid. The results revealed that coating of fruits resulted in reduced loss in fruit weight and higher level of ascorbic acid content, TSS, acidity, total sugar, reducing sugar as compared to the fruits under control. The most effective coating was Guar gum (2%) that extended the shelf life of ber up to 16 days. Fruits under control had a shelf life of only10 days
Test of conformal theory of gravity as an alternative paradigm to dark matter hypothesis from gravitational lensing studies
Weyl's conformal gravity theory, which is considered as a compelling
alternative to general relativity theory, has been claimed to describe the
observed flat rotation curve feature of spiral galaxies without the need of
invoking dark matter. However, it is important to examine whether the Weyl
theory can also explain the relevant gravitational lensing observations
correctly without considering any dark matter. In this regard, the
gravitational bending angle in static spherically space-time (Mannheim-Kazanas
metric) in Weyl theory has been calculated by several authors over the last two
decades, but the results are found largely divergent. In this work, we have
revisited the problem and obtain the correct and consistent expression of the
deflection angle in conformal gravity. Subsequently we perform the
gravitational lensing analysis. We compare the prediction of Weyl gravity with
the gravitational lensing observations of the rich galaxy clusters Abell 370
and Abell 2390 and is found that Weyl theory cannot describe the stated lensing
observations without considering dark matter.Comment: 9 page
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