Cosmological Constant: QFT and Existence Explained

[paweld]

How QFT might possibly explain existence of cosmological constant.
Does it predict that vacuum stress energy tensor has on it's diagonal
positive time component (density of energy) and negative spatial
components (preasure=-density)?

 

[Chalnoth]

How QFT might possibly explain existence of cosmological constant.
Does it predict that vacuum stress energy tensor has on it's diagonal
positive time component (density of energy) and negative spatial
components (preasure=-density)?

Well, it does, but it gets the magnitude completely wrong (off by a factor of 10^120).

 

[paweld]

Let's forget for a moment about this factor. I'm interested in more general problem.
Is true at least that vacuum stress energy tensor
has on it's diagonal positive time component (density of energy) and negative spatial
components (preasure=-density), so that it could play similar role as cosmological
constant?

 

[Chalnoth]

Let's forget for a moment about this factor. I'm interested in more general problem.
Is true at least that vacuum stress energy tensor
has on it's diagonal positive time component (density of energy) and negative spatial
components (preasure=-density), so that it could play similar role as cosmological
constant?

If the vacuum has a constant energy density, one that is independent of space and time, then it is a cosmological constant.

 

[paweld]

If the vacuum has a constant energy density, on that is independent of space and time, then it is a cosmological constant.

Thanks