Gamma in Brans-Dicke framework

In summary, the present study examines the empirical relation of Φ=Φ0(a/a0)n, where n=-(dG/dt)/GH, and finds that n is negative, indicating an increase in G with time. This fact is used to evaluate ϒ using a scale factor of the form sinh(t) and the resulting plot is consistent with other studies. The study also shows that for a universe dominated by radiation and matter, ϒ increases before transitioning to negative values, contradicting previous research. However, the credibility of this study may be questionable due to its publication in a predatory journal and the potential lack of awareness of current evidence.
  • #1
Apashanka
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IMG_20190215_215221.jpg

I take an empirical relation of Φ=Φ0(a/a0)n where n=-(dG/dt)/GH ,present study shows n is negative ,implies that G increases with time
And using this fact and taking a scale factor of the form sinh(t) ,evaluated ϒ and then plot it with respect to t and got the above figure which is consistent with many other work done.
Present study shows ϒ(n,t0)=-0.67 to -1.67
n is chosen in such a way in the above plot.
From the plot it is concluded the transition time of positive pressure to negative pressure and start up time of the accelerated expansion.
But if we consider our universe to be dominated by radiation at very early epoch followed by matter then ϒ decreases from 1/3 to 0 and then -ve but this study and many other study shows ϒ increases first and then transit to -ve value as shown in the plot??
Is there is something which I am missing
 

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  • #2
Where is all this coming from? What "study" are you talking about? What are ##\Phi## and ##\Upsilon##?
 
  • #3
PeterDonis said:
Where is all this coming from? What "study" are you talking about? What are ##\Phi## and ##\Upsilon##?
Φ is the scaler field of Brans-Dicke theory and ϒ is of pressure relation P=ϒρ ,ρ is the energy -density
 
  • #5
Dale said:
Please cite the study also
Page 4731
 

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  • #6
Research India Publications is a known predatory publisher. I would be highly skeptical of anything found only in one of their journals.

Current evidence places the ##\omega## parameter at somewhere greater than 40000. The paper talks about ##\omega## on the order of unity, so I get the impression that the author may be unaware of the evidence. This could be a likely reason that the paper wound up in a predatory journal. I would not spend too much time on it.
 
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1. What is the Gamma parameter in the Brans-Dicke framework?

The Gamma parameter is a fundamental constant in the Brans-Dicke theory of gravity, which is an alternative theory to Einstein's theory of general relativity. It is represented by the Greek letter gamma (Γ) and is used to describe the strength of the coupling between matter and the gravitational field.

2. How does the Gamma parameter affect the behavior of gravity in the Brans-Dicke framework?

The value of the Gamma parameter determines the strength of the gravitational force in the Brans-Dicke theory. A higher value of gamma leads to a weaker gravitational force, while a lower value results in a stronger gravitational force. This parameter also affects the speed of gravitational waves and the bending of light in the presence of massive objects.

3. Can the Gamma parameter be measured or observed in experiments?

Yes, the Gamma parameter can be measured or constrained through various experiments and observations. For example, the parameter can be determined by studying the orbits of planets around the Sun, the bending of starlight by massive objects, and the behavior of gravitational waves. These observations can help to determine the value of gamma and test the predictions of the Brans-Dicke theory.

4. How does the Gamma parameter relate to the cosmological constant?

The cosmological constant is a term in Einstein's theory of general relativity that represents the energy density of empty space. In the Brans-Dicke framework, the Gamma parameter is related to the cosmological constant through the field equations that govern the behavior of gravity. A non-zero value of gamma can lead to a non-zero cosmological constant, which can have implications for the expansion rate of the universe.

5. Are there any theoretical implications of the value of the Gamma parameter?

Yes, the value of the Gamma parameter has important theoretical implications for the Brans-Dicke theory and its predictions. For instance, a high value of gamma can lead to a violation of the equivalence principle, which states that the gravitational and inertial mass of an object are equivalent. Additionally, the value of gamma can affect the stability and predictability of the theory, as well as its compatibility with other theories such as quantum mechanics.

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