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

The bounce.

  1. Apr 23, 2005 #1


    User Avatar
    Gold Member

    http://rainman.astro.uiuc.edu/coffeepap_Friday.html [Broken]

    Title: Can the initial singularity be detected by cosmological tests?
    Authors: Marek Szydlowski, Wlodzimierz Godlowski, Adam Krawiec, Jacek Golbiak
    Comments: 30 pages, 7 figures

    In the present paper we raise the question whether initial cosmological singularity can be proved from the cosmological tests. The classical general relativity predict the existence of singularity in the past if only some energy conditions are satisfied. On the other hand the latest quantum gravity applications to cosmology suggest of possibility of avoiding the singularity and replace it with the bounce. The distant type Ia supernovae data are used to constraints on bouncing evolutional scenario where square of the Hubble function $H^2$ is given by formulae $H^2=H^2_0[\Omega_{m,0}(1+z)^{m}-\Omega_{n,0}(1+z)^{n}]$, where $\Omega_{m,0}, \Omega_{n,0}>0$ are density parameters and $n>m>0$. We show that the on the base of the SNIa data standard bouncing models can be ruled out on the $4\sigma$ confidence level. If we add the cosmological constant to the standard bouncing model then we obtain as the best-fit that the parameter $\Omega_{n,0}$ is equal zero which means that the SNIa data do not support the bouncing term in the model. The bounce term is statistically insignificant the present epoch. We also demonstrate that BBN offer the possibility of obtaining stringent constraints of the extra term $\Omega_{n,0}$. The other observational test methods like CMB and the age of oldest objects in the Universe are used. We also use the Akaike informative criterion to select a model according to the goodness of fit and we conclude that this term should be ruled out by Occam's razor, which makes that the big bang is favored rather then bouncing scenario.
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Apr 23, 2005 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    I notice that even though they don't connect with Loop Quantum Cosmology (their "bouncing model" given in their equation (1) is different from LQC) they at least mention Bojowald's work in their conclusions.

    So at least they are aware of it. But their paper does not bear on LQG. They are studying a "bouncing model", as in eqn. (1), which behaves differently and from which the conclusions do not apply. It is too bad if one gets the impression from some verbal suggestions that it has something to do with Loop, but one can see from their equations, both in the paper itself, and also already in the abstract, that it doesnt.
    Last edited: Apr 23, 2005
  4. Apr 23, 2005 #3


    User Avatar
    Science Advisor
    Gold Member

    I read that paper yesterday and did not find it very convincing. Out of curiousity I browsed through some other works by Szydlowski. He is no stranger to unconventional theories.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook