Cosmological Constant: QFT and Existence Explained

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Discussion Overview

The discussion centers on the relationship between quantum field theory (QFT) and the cosmological constant, particularly exploring whether the vacuum stress energy tensor can account for the cosmological constant's characteristics. The scope includes theoretical considerations and conceptual clarifications regarding energy density and pressure in the context of QFT.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that QFT predicts the vacuum stress energy tensor has a positive time component (density of energy) and negative spatial components (pressure = -density).
  • Others argue that while QFT does predict this, the magnitude of the cosmological constant derived from QFT is significantly incorrect, being off by a factor of 10^120.
  • A later reply suggests that regardless of the magnitude issue, the vacuum stress energy tensor could still play a role similar to that of the cosmological constant if it has a constant energy density that is independent of space and time.

Areas of Agreement / Disagreement

Participants express differing views on the significance of the magnitude discrepancy in QFT predictions regarding the cosmological constant. There is no consensus on the implications of this discrepancy, and the discussion remains unresolved regarding the broader implications of the vacuum stress energy tensor.

Contextual Notes

The discussion does not resolve the assumptions regarding the nature of vacuum energy or the implications of the magnitude discrepancy in the context of cosmological models.

paweld
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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)?
 
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paweld said:
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).
 
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?
 
paweld said:
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.
 
Last edited:
Chalnoth said:
If the vacuum has a constant energy density, on that is independent of space and time, then it is a cosmological constant.
Thanks
 

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