Meaning of cosmological constant ?

AI Thread Summary
The cosmological constant has significant implications for the universe's evolution, with its value typically expressed in energy units rather than dimensions of 1/R^2. It remains constant over time, contrary to the misconception that its energy density evolves with the scale factor. The correct dimensional representation is 1/L^2, indicating a relationship to energy density in geometrized units of general relativity. To explore the deeper meaning of the cosmological constant's length scale, one should refer to advanced literature, such as Padmanabhan's work on the topic. Understanding these concepts requires careful study of the underlying physics and mathematics.
notknowing
Messages
185
Reaction score
0
Incredibly much has been written about the cosmological constant and all its implications on the evolution of the universe. I want to ask however a more basic question about it. The cosmological constant has the dimension of 1/R^2. So supposing this constant is non-zero, its value points to the existence of some characteristic distance or radius. The Schwarzschild radius for instance has a clear understandable meaning but what could be the meaning of the radius associated with the cosmological constant? The only thing which comes to (my) mind is the radius of the universe itself. What other opinions exist (or are described in literature - related to "radius")?


Rudi Van Nieuwenhove
 
Space news on Phys.org
The cosmological constant has a value whose units are energy. I'm not sure what you mean by saying 'it has the dimensions of 1/R^2"?

If you mean that the energy density of the cosmological constant evolves as 1/R^2 where R is the scale factor that is incorrect. Curvature evolves in that way (in the way it is represented in cosmology) but the cosmological constant, unsurprisingly, remains constant for all time.
 
The dimensions of 1/L2 for the cosmological constant are correct in the usual geometrized unit system of general relativity. To find a deeper meaning to such a length scale one should go beyond general relativity, see for example section 7 of Padmanabhan's Cosmological Constant - the Weight of the Vacuum.
 
It might help to point out that in geometric units, energy density (and sectional curvatures, e.g. the components of the Riemann curvature tensor) have the units of reciprocal area. Since Lambda contributes a diagonal term to the stress-energy tensor of our spacetime models, with the entries proportional to Lambda (in any frame!), this represents an energy density and has the units of reciprocal area.
 
hellfire said:
The dimensions of 1/L2 for the cosmological constant are correct in the usual geometrized unit system of general relativity. To find a deeper meaning to such a length scale one should go beyond general relativity, see for example section 7 of Padmanabhan's Cosmological Constant - the Weight of the Vacuum.


Thanks for this interesting reference. This means a lot of reading (114 pages)!
 

Thread 'Illuminating Black Hole Shadows with Dark Matter Annihilation'

Abstract The Event Horizon Telescope (EHT) has significantly advanced our ability to study black holes, achieving unprecedented spatial resolution and revealing horizon-scale structures. Notably, these observations feature a distinctive dark shadow—primarily arising from faint jet emissions—surrounded by a bright photon ring. Anticipated upgrades of the EHT promise substantial improvements in dynamic range, enabling deeper exploration of low-background regions, particularly the inner shadow...
View full post »

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##.
View full post »

Similar threads

I Age of the Universe and the Cosmological Constant
Replies
17
Views
2K
B Cosmological constant for the Universe's expansion
Replies
5
Views
2K
I Questions on the consequence of an evolving dark energy parameter
Replies
1
Views
1K
I Einstein, Friedman and the cosmological constant
Replies
5
Views
2K
I Meaning of the distance between galactic objects in GR
Replies
9
Views
3K
B History of Cosmology: 1915-1929 | Einstein, Hubble & GR
Replies
19
Views
3K
B How does the cosmological constant affect gravitational collapse?
Replies
2
Views
2K
A Dark energy = cosmological constant, any problems with that?
4
Replies
153
Views
12K
I 3 questions about a paper on density fluctuations in the Universe
Replies
1
Views
2K
Dark energy and the Cosmological Constant
Replies
37
Views
4K

Hot Threads

Recent Insights

Back
Top