marcus said:I have never heard any evidence that "quintessence" is real. Have you?
If it is not a real thing, then there would be no correct value of the parameter M.
My impression is that quintessence is an idea that people used to talk about back around 2003---over 5 years ago anyway. And it turned out to be an unnecessary complication. So it went out of style.
So the professional cosmologists don't talk about quintessence very much, except to rule it out or show it is unnecessary to the model when they get some new data.
(Every time you get a new batch of data, it is one of the things you consider, and check to see that it still is unnecessary.)
Have you seen some recent scientific journal articles about it? Have I missed something?
marcus said:Dear Shadi, I probably won't be able to help but others might. The first thing is to post the name of the Steinhardt article, if possible a link. Then we can see what you are talking about in context.
Oh! I think you may mean this one:
http://arxiv.org/abs/astro-ph/9807002
Quintessence, Cosmic Coincidence, and the Cosmological Constant
Ivaylo Zlatev (1), Limin Wang (1), Paul J. Steinhardt (1 and 2) ((1) University of Pennsylvania, (2) Princeton University)
(Submitted on 1 Jul 1998 (v1), last revised 21 Oct 1998 (this version, v2))
Recent observations suggest that a large fraction of the energy density of the universe has negative pressure. One explanation is vacuum energy density; another is quintessence in the form of a scalar field slowly evolving down a potential. In either case, a key problem is to explain why the energy density nearly coincides with the matter density today. The densities decrease at different rates as the universe expands, so coincidence today appears to require that their ratio be set to a specific, infinitessimal value in the early universe. In this paper, we introduce the notion of a "tracker field", a form of quintessence, and show how it may explain the coincidence, adding new motivation for the quintessence scenario.
4 pages, 4 figures
The mass parameter for quintessence is a fundamental constant that characterizes the strength of the interaction between quintessence particles and other particles in the universe. It is denoted by the symbol m and has units of mass.
The mass parameter determines the range and strength of the quintessence force. A larger mass parameter results in a shorter range and a stronger force, while a smaller mass parameter leads to a longer range and a weaker force.
The mass parameter for quintessence is typically assumed to be constant, but some theories suggest that it may vary over time. This would have significant implications for the behavior of quintessence and its impact on the expansion of the universe.
Quintessence is a type of dark energy, and the mass parameter plays a crucial role in determining its properties and behavior. It is one of the key parameters in equations describing the evolution of dark energy and its effect on the expansion of the universe.
Currently, there is no direct way to measure the mass parameter for quintessence. It is typically determined by fitting theoretical models to observational data from astronomical surveys and experiments. However, ongoing research may lead to new methods for measuring this fundamental constant in the future.