Unveiling the Mystery of the Cosmological Constant: A Fresh Perspective on CC

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Discussion Overview

The discussion centers around the nature and implications of the cosmological constant (cc), particularly whether it is truly constant or may vary over time. Participants explore theoretical and observational aspects, questioning the assumptions underlying current models and measurements.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants assert that the current value of the cc is determined by observations, raising the question of its potential variability over time.
  • One participant expresses uncertainty about how changes in the cc could be detected, using a hypothetical scenario of a sudden increase.
  • Another participant argues that current estimates of the cc are heavily reliant on assumptions within the Friedmann-Walker-Robertson (FWR) equations, which may not be sufficiently validated by experimental evidence.
  • This participant also questions whether factors like extra-horizon mass distributions and inhomogeneities could influence the cc, expressing agnosticism about its constancy.
  • A distinction is made between a truly constant cc and phenomena that might appear to vary, suggesting that if the cc is part of General Relativity (GR), it should remain constant as it is an integration constant.
  • There is speculation about the possibility of dark energy being distributed in a way that could mimic a varying cc, though this participant maintains that such a scenario would not constitute a true cosmological constant.

Areas of Agreement / Disagreement

Participants do not reach a consensus; multiple competing views regarding the nature of the cosmological constant and its potential variability remain evident throughout the discussion.

Contextual Notes

Participants highlight limitations in current models and measurements, including assumptions that may not be universally accepted or experimentally confirmed, as well as the potential for inconsistencies in estimating the Hubble constant.

wolram
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What is your view on what the cosmological constant is?
 
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The current value of the cc is whatever observations tell us. The major question of interest is whether or not it changes with time.
 
mathman said:
The current value of the cc is whatever observations tell us. The major question of interest is whether or not it changes with time.

I may be missing some thing, but how would we know, if for instance it
increased by 100% on 20 april?
 
I think that our estimates are too dependent upon assumptions that go into the FWR equations (and the FWR model itself) in ways that are insufficiently confirmed by experiment to definitely put a value on the cc that will stand the test of time.

Issues such as: Could an extra-horizon mass distribution have an impact, are imhomogenities sufficiently great to make an impact, and are all of the multiple different methods of estimating the Hubble constant mutually consistent within their error bars, leave me agnostic on the issue.

In my mind a pheneomena that would appear to be a varying cc is wrong as a matter of definition. Either you have a cc which is constant, or you have some other phenomena which varies, or you have both. Constants don't vary. If cc is part of the GR equations then is must be a constant and not a function, because it arises as an integration constant. But, if it varies, it is a function.

Could there be dark energy distributed in such a way that it mimics one cc at this time period and another when the universe was 1% of its current age? Probably. But, in my mind, that wouldn't be a cc.
 

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