Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Cosmological constant and vacuum energy

  1. Apr 27, 2013 #1


    User Avatar

    Since Omega-lambda is very close to Omega-matter, what could it mean if we assume they are exactly equal to each other. Also, lets assume they were always equal since coincident problem is unnatural.
  2. jcsd
  3. Apr 27, 2013 #2
    Your use of terms is misleading in regards to your question.
    In the title the vacuum energy is the same as the cosmological constant, lambda.

    In your omega-matter, are you referring to the total mass including DM, radiation and energy. Or specifically just normal matter?

    What you are probably looking for is the relation of the critical density vs lambda. Please confirm

    Here is a quick article on critical density
  4. Apr 27, 2013 #3


    User Avatar

    Thanks for the reply. Yes, you are right of course , first I used slash but I just added and., just a title. As for the question I am hypothesising if there was no dark matter just ordinary matter energy and vacuum energy. And both should add up to critical density.
  5. Apr 27, 2013 #4
    Your still not being clear so I will assume the intent.

    If the total actual density equals (exactly and stable) equals the critical density then the universe is flat and static.

    Judging from your descriptives you may not understand why that is the answer.

    in short the relation between critical density and actual density determines not only spacetime geometry but also expansion rates.

    Last edited: Apr 27, 2013
  6. Apr 28, 2013 #5


    User Avatar
    Science Advisor
    Gold Member

    They don't, which is one reason dark matter is the favored explanation. We can strongly constrain the contribution of omega baryonic and omega lambda to critical density, and they fall far short of that necessary to account for the measured critical density of the universe.
  7. Apr 28, 2013 #6
    add to that the contributions of omega-relativististic particles such as neutrinos (in relativistic energy levels) or other factors to overall actual energy-mass density factors (radiation/energy
  8. Apr 28, 2013 #7
    One of the problems associated with forum based answers. Is the specific need of clarity on what the OP is asking for. This requires accurate feedback from the OP. Not only on a specified target but also a target of understanding vs the OP's line of thinking.

    To answer your questions accurately in an educational manner requires us to formulate your thoughts. This is indicative of why I ask for better clarity on your understanding on the
    related post
    Last edited: Apr 28, 2013
  9. Apr 30, 2013 #8


    User Avatar

    ok Thanks. I have been going through some books to get some more info, but I am getting a bit confused. So I hope I can clarify my question shortly. but yes, it seems a static universe is the answer like the great blunder of Einstein. But I wonder what values he used.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook