Relationship between energy density and cosmological constant

[novice_hack]

TL;DR

According to the wiki entry on Planck units, https://en.wikipedia.org/wiki/Planck_units, the energy density of the universe, 1.8 × 10−123, is 1/16th the cosmological constant, 2.9 × 10−122. Is there a theoretical reason for this precise relationship?

According to the wiki entry on Planck units, https://en.wikipedia.org/wiki/Planck_units, the energy density of the universe, 1.8 × 10−123, is 1/16th the cosmological constant, 2.9 × 10−122. Is there a theoretical reason for this precise relationship?

 

[EigenState137]

According to the wiki entry on Planck units, https://en.wikipedia.org/wiki/Planck_units, the energy density of the universe, 1.8 × 10−123, is 1/16th the cosmological constant, 2.9 × 10−122. Is there a theoretical reason for this precise relationship?

Greetings,

Any reason there should be a physcially significant reason?

The number you quoted for energy-density is actually specified as density in units of Planck mass per unit Planck volume.ES

 

[PeterDonis]

Is there a theoretical reason for this precise relationship?

The relationship is not a constant; it changes with time, because the energy density of the universe decreases as it expands, while the energy density of the cosmological constant does not.

 

[novice_hack]

Greetings,

Any reason there should be a physcially significant reason?

The number you quoted for energy-density is actually specified as density in units of Planck mass per unit Planck volume.ES

The relationship is not a constant; it changes with time, because the energy density of the universe decreases as it expands, while the energy density of the cosmological constant does not.

Ok. Call it mass density. I am asking whether there is some reason that there would be a relationship between the two. Maybe the answer is 'no'. It just seems curious to me that the one value is 16 times the other value. It seems like the kind of thing for which there might be some theoretical explanation. Perhaps it is just a peculiar coincidence.

 

[EigenState137]

Greetings,

Why do you find the value of 16 to be possibly special? Just because it happens to be an integer?ES

 

[novice_hack]

I am assuming from your questions that either you think the answer to the question is 'no' or that you don't know the answer.

 

[PeterDonis]

I am asking whether there is some reason that there would be a relationship between the two.

And I have already told you that there is no such "relationship", because the ratio between the cosmological constant and the matter density (or mass density, or energy density, or whatever you want to call it) in the universe changes with time. So your question is based on a false premise, that the current value of 16 (which isn't exactly 16 anyway) is an unchanging value that needs an explanation.

 

[EigenState137]

I am assuming from your questions that either you think the answer to the question is 'no' or that you don't know the answer.

Greetings.

If that post is addressed to me, what I am asking is exactly what I posted. Why do you consider the numerical value of 16 to be possibly special and perhaps indicative of something physically significant?

That question has nothing to do with what @PeterDonis has already explained to you that the ratio is time-dependent.ES