Is dark energy or dark matter created to keep the Cosmological constant

[arunshanker]

A positive value for the cosmological constant was found by the studies of Adam G. Riess et al and Pearlmutter et al
In terms of Planck units, and as a natural dimensionless value, the cosmological constant, λ, is on the order of 10−122 or 10−29 g/cm3
The cosmological constant has negative pressure equal to its energy density and so causes the expansion of the universe to accelerate.
The universe is accelerating and space is expanding
Does it mean that new space is being created and if so what is the cosmological constant in the new space or expanded space
If suppose an area of space has a cosmological constant value of 10−29 g/cm3 then if it expands what will be the value of consmological constant as the word itself says it is constant
Is dark energy or dark matte created to keep this constant

 

[mfb]

Does it mean that new space is being created and if so what is the cosmological constant in the new space or expanded space

You cannot point to anything in space and say "this space is new". Everything expands with the same rate (ignoring some local collections of matter). The cosmological constant itself could vary with time, but no variation has been found yet.

 

[Naty1]

Hi arun...lots of unknowns remain to be discovered...

If suppose an area of space has a cosmological constant value of 10−29 g/cm3 then if it expands what will be the value of consmological constant as the word itself says it is constant
Is dark energy or dark matte created to keep this constant

The energy density is believed to remain constant with the metric expansion of the cosmos. So as the universe expands, the total vacuum energy increases and its repulsive nature causes space to expand even faster…in a run away exponential expansion. In the big bang model, dark energy [the cosmological constant] powers an accelerated expansion after about 7 or 8B years as it overpowers the gravitational attraction of matter. We are already moving from a 'matter dominated' to an 'energy dominated' epoch. Dark matter dominated the past; dark energy will dominate the future.

I get the sense 'dark energy' may be less popular now than in the recent past...at least by some in these forums... and that perhaps it is just a feature of curved space time that leads to some gravitational repulsion at vast distances...

Dark matter and dark energy are so far two distinct and virtually unrelated 'unknowns'... which is what 'dark' means. We infer the existence of dark matter by its gravitational effects; We infer the existence of dark energy by the accelerated expansion of space...dark matter seems to aid the formation of galaxies a bit; dark energy may slow formation a bit.

Here is what Bianchi and Rovelli have to say about the cosmological constant...dark energy...vacuum energy...call it what you want...

Why all these prejudices against a constant?
Eugenio Bianchi, Carlo Rovelli
(Dated: April 13, 2010)

IV. THE VACUUM ENERGY IN QUANTUM FIELD THEORY

...Finally, let us come to the argument that many considered the strongest against the cosmological constant scenario: the quartic divergence of the vacuum energy density in quantum feld theory (QFT). To begin with, here is a naive version of the argument: a formal quantization of a field theory leads to a divergent energy for the vacuum state. If we assume that divergences are controlled by a physical cut-off, say at the Planck scale, {an ultra-violet cutoff?} then the theory predicts a Planck-scale vacuum energy. This behaves like an effective cosmological constant. Therefore one can say that QFT predicts the existence of a cosmological constant. However, the predicted cosmological constant has a value which is about 120 orders of magnitude larger that the observed one. Thus, the cosmological constant is predicted by particle physics, but the prediction is quantitatively wrong by 120 orders of magnitude (The worst theoretical prediction in the history of physics")

 

[Jorrie]

Hubble Constant at end of inflation

I have a related question. If we wind the FRW equations back from the time of matter-radiation equality (z~3300), ignoring matter and Lambda densities (they were small before that) to the end of inflation, I get order of magnitude:
[tex]
H(t) \approx H_0\sqrt{\frac{\Omega_{rad}}{a^4}} \approx 10^{56} H_0
[/tex]
I used for end of inflation: [itex]a \approx 10^{-28}[/itex] and [itex]\Omega_{rad} = \Omega_m/z_{eq}\approx 10^{-4}[/itex], the present value.

Would that H(t) be roughly the constant H (and related Hubble radius) during inflation? This would mean that the cosmological constant must 'jump' into domination around that point (running time backwards), swamping any radiation density.

 

[sardar]

I cannot provide a definitive answer to this question as the nature and origin of dark energy and dark matter are still unknown and subject to ongoing research and debate. However, I can provide some insights and perspectives on this topic.

Firstly, it is important to clarify that dark energy and dark matter are two distinct concepts. Dark energy refers to the mysterious force that is causing the expansion of the universe to accelerate, while dark matter refers to the unseen matter that is thought to make up about 85% of the total matter in the universe. Both of these concepts are still not fully understood and their existence is inferred from their gravitational effects on visible matter and light.

In terms of the cosmological constant, it is a parameter in Einstein's theory of general relativity that represents the energy density of the vacuum or empty space. It was originally introduced by Einstein to explain a static and unchanging universe, but subsequent observations have shown that the universe is indeed expanding. The positive value of the cosmological constant, as found by the studies mentioned in the question, suggests that the expansion of the universe is accelerating. This is consistent with the observed effects of dark energy.

As for the question of whether dark energy or dark matter is created to keep the cosmological constant constant, this is a matter of ongoing research and debate. Some theories suggest that dark energy and dark matter may be related to the cosmological constant, while others propose alternative explanations. It is also worth noting that the value of the cosmological constant may not necessarily be constant in all areas of space, as it can vary depending on the density and distribution of matter and energy. The concept of "new space" being created is also a subject of theoretical speculation and has not been confirmed by observations.

In conclusion, while the cosmological constant and its relation to dark energy and dark matter are still not fully understood, ongoing research and observations are helping us to gain a better understanding of the fundamental forces and components that make up our universe.