Talk:Quintessence (physics)
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What Cosmological Constant?
[edit]I assume what is meant is that with a fixed value w would be a cosmological constant. Doesn't that contradict the role in the observed accelerating expansion though? Article could use some attention. Lycurgus 00:47, 30 May 2007 (UTC)
Einstein's general relativity (GR) assumes his Cosmological Constant(CC) - a specific nomber in GR - has w = -1 everywhere and everywhen. Quintessence (Q) sets w = -1/3 to match observational data supporting accelerating expansion. The distinction between the two is that,in Q, vacuum pressure and density(proportionately) decrease with time as the universe expands. Both theories maintain a constant lightspeed. Other theories, under development, assume lightspeed increases when pressure (i.e. vacuum energy density, a.k.a. Zero Point Field density) decreases. C. Lee Robins, physicist. 66.59.230.158 15:51, 16 September 2007 (UTC)
Quintessence vs. Inflation
[edit]Hi, is there anyone who could explain what the difference is between quintessence and inflation? This might be of interest for this article.
René 20.32 (CET), 15 June 2007
Quintessence is a modification to Einstein's General Relativity which seeks to explain an observed increase in the rate at which the universe is expanding/inflating. (This increasing rate is not predicted by GR) C. Lee Robins, physicist 66.59.230.158 15:46, 16 September 2007 (UTC)
- Well, yes, this is the meaning of quintessence, but what about inflation? Inflation is a scalar field which has caused an accelerated expansion in the early ages of the universe, as quintessence currently does. However, quintessence and inflation are different, but what exactly is the difference?
- René 20.46 (CET), 01 October 2007 —Preceding unsigned comment added by 62.227.255.237 (talk) 18:48, 1 October 2007 (UTC)
and Q is ? HOw ABOUT DEFINING EACH TERM! — Preceding unsigned comment added by 75.163.191.55 (talk) 22:07, 19 November 2015 (UTC)
Universe Age
[edit]The article claims to give an age to the universe, when in fact it should be giving that age to the known universe. The entire Universe is not explored, nor do I believe it ever will be, it is for all we know infinite in age. What we know of as our known universe is not the entire universe, it seems misleading to give a number to the entire universe when we do not even know. 50.47.99.169 (talk) 13:46, 18 August 2013 (UTC)
I don't know how the talk page works, but the quotes in the paragraph about aether are unsourced. I think that's a bad thing
-That one guy. — Preceding unsigned comment added by 47.49.166.206 (talk) 17:00, 8 April 2019 (UTC)
Phantom energy
[edit]The article claims that phantom energy is a class of quintessence, however this is incorrect. Quintessence and phantom fields are distinct entities. The first has a positive kinetic term in the Lagrangian density, while the latter has a negative one. Furthermore, the paper cited does not refer to quintessence but rather to phantom fields. Crossing the phantom divide line (wq = -1) in a continuous manner is not possible, as such transition would require a change in the sign of the kinetic term, which is inherently fixed in both quintessence and phantom field models. Consequently, there is no mechanism by which a quintessence field can attain wq < -1. As correctly noted earlier in the article, the equation of state parameter for quintessence can only take values in the range [-1, 1].