Amount of dark Energy at different times

AI Thread Summary
The discussion focuses on calculating the amount of dark energy in the observable universe at different times, specifically using a formula that relates dark energy to the scale factor. It suggests that dark energy density could be expressed as inversely proportional to the cube of the scale factor, indicating that dark energy was about one-fourth of its current amount 6 billion years ago. However, it emphasizes that total energy is not well-defined in General Relativity, making density a more useful measure. The radius of the observable universe does not scale directly with the scale factor, and the correct scale factor for 6 billion years ago is clarified to be approximately 0.618. Overall, the conversation highlights the complexities of measuring dark energy and the importance of understanding its density over time.
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I am wondering what the formula would be for the amount of Dark Energy in the observable universe would be for different time (t). (according to best current theory/data)

Would it be this directly proportional to volume?
Dark energy (t) = Dark energy (present time)/ (scale factor (t)3)

If so, 6GY ago scale factor = 1.618 therefore Dark Energy would be about 1/4 the current amount.

I could be way off as I am just starting on this stuff.
 
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I don't think that the amount of dark energy is a useful quantity (total energy is not well-defined in General Relativity). The density, however, is useful, and can be thought of as a constant (if it does change over time, those changes haven't yet been detected).
 
Apart from what Chalnoth said about the usefulness of total energy, the radius of the observable universe does not scale directly with scale factor a. You mentioned a=1.618, which is in the future, so I guess you intended to say a=0.618, which correlates with 6 Gy ago.
The radius of the observable universe was then about half of what it is today ( D_particle ~ 23 Gly then, according to LightCone 7) and the total vacuum energy in the observable universe about one eighth of today (at constant density).
 
Jorrie: That clarifies what I was looking to understand. I also was not using scale factor term correctly.
Thanks
 

Thread 'Matter density right after the decoupling'

https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
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Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?
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