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LambdaCDM inflation model dependancies

  1. Apr 26, 2013 #1
    I've been haqving a tough time tracking down which particular inflationary models form the basis of [itex]\Lambda[/itex]CDM.

    the model I have discounted already is false vacuum A.Guth. some articles seem to suggest concepts from slow roll inflation. Others deal specifically with the inflaton field in the early universe inflation so I'm thinking eternal inflation is still used. I'm still looking for data on Roulette inflation just heard about it today lol.

    Part of the problem with my search is that there is lots of misleading data on the search. Also the [itex]\Lambda[/itex]CDM model may derive from multiple inflationary models.

    Any direction would be helpful, its more a curiousity on my part.

    needless to say their is numerous inflationary models, I've been compiling a list of the variations
    Last edited: Apr 26, 2013
  2. jcsd
  3. Apr 26, 2013 #2
    So far my list of related include:

    tunneling models:
    (i) double-field inflation (Adams and Freese)
    (ii) extended inflation (Steinhardt)
    (iii) Chain inflation (Freese and Spolyar))

    2) Rolling Models:
    new inflation,
    chaotic inflation,
    hybrid inflation
    Natural inflation (Freese,
    Frieman, Olinto)

    edit:: if my understanding of the group seperation between otunneling models and rolling models, fundamentally it can be seperated into degrees of freedom.

    Still not clear on how to place slow roll. In terms of the above categories
    Last edited: Apr 27, 2013
  4. Apr 27, 2013 #3


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    The tough time does not seem so surprising to me because AFAIK there is no particular inflation that is basis for LCDM.

    LCDM starts expansion with certain conditions, e.g. near flatness, near isotropy, a fluctuation spectrum appropriate for seeding structure.

    People are free to imagine various scenarios calculated to produce these conditions. I don't think anyone has proven logically that ONLY SOME INFLATION scenario is capable of yielding these initial conditions.

    I would say that so far there is NO one unique inflation scenario that "forms the basis" for LCDM.

    People would do well to watch this talk by Paul Steinhardt, a world-class cosmologist who was one of the principle inventors of inflation. He seems to have now rejected it as a front-end prep for LCDM and is working on an alternative front-end scenario for LCDM.

    Here's what Perimeter says about Steinhardt:
    "Currently the Albert Einstein Professor in Science, and on the Faculty of both the Department of Physics and the Department of Astrophysical Sciences at Princeton University, Dr. Steinhardt is one of the leading theorists responsible for inflationary theory. He constructed the first workable model of inflation and the theory of how inflation could produce seeds for galaxy formation. Among his awards is the 2002 Paul Dirac Medal of the International Centre for Theoretical Physics"

    After being one of the principal inventors of inflation, he is now busy showing that LCDM does not require inflation.

    Basically LCDM is a classic model of expansion cosmology once it got started.

    People have speculations scenarios and opinions about how it got started (and these include various inflations and bounces) but they are not part of LCDM proper.
  5. Apr 27, 2013 #4


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    To balance the mention of Steinhardt with another major figure, consider Abhay Ashtekar.

    The Springer press publishes a line of scientific Handbooks, and they are now bringing out a
    Handbook of Spacetime, with Ashtekar as editor. From the looks of it this is going to be a massive project. Many top experts have been recruited to write chapters. the aim is to represent the state of the art in our understanding of spacetime geometry, gravity, cosmology.

    Well, this his current take on a front end for the LCDM. He accepts a version of slow-roll inflation but then because THAT ITSELF NEEDS EXPLAINING he puts a pre-inflation stage in front of that to create the necessary conditions for a satisfactory inflation episode. And he is concerned with observational tests of this. Go figure :biggrin:

    The pre-inflationary dynamics of loop quantum cosmology: Confronting quantum gravity with observations
    Ivan Agullo, Abhay Ashtekar, William Nelson
    (Submitted on 1 Feb 2013)
    Using techniques from loop quantum gravity, the standard theory of cosmological perturbations was recently generalized to encompass the Planck era. We now apply this framework to explore pre-inflationary dynamics. The framework enables us to isolate and resolve the true trans-Planckian difficulties, with interesting lessons both for theory and observations. Specifically, for a large class of initial conditions at the bounce, we are led to a self consistent extension of the inflationary paradigm over the 11 orders of magnitude in density and curvature, from the big bounce to the onset of slow roll. In addition, for a narrow window of initial conditions, there are departures from the standard paradigm, with novel effects ---such as a modification of the consistency relation between the ratio of the tensor to scalar power spectrum and the tensor spectral index, as well as a new source for non-Gaussianities--- which could extend the reach of cosmological observations to the deep Planck regime of the early universe.
    64 pages, 15 figures. Published version
  6. Apr 27, 2013 #5


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    There are hundreds of inflationary models, and you can read the latest planck papers to see which are still consistent with the data. To start, this paper (http://arxiv.org/abs/1303.3787) compiles an encyclopaedia of solely single field inflation models, and splits them into different classes.
  7. Apr 27, 2013 #6
    Thanks for the link. The method you described is how I had generated the above list. I've been pouring over LCDM to inflationaty paradigm reviews. The above models are still considered good fits to observational data. Whether in part or overall.

    Thanks for the above info on Steinhard Marcus. LQC I will eventually study if you happen to have a good step by step from the LQC original derivitaves to current development training articles. That will make my future LQC studies easier.

    As you can see I enjoy studying the history of development. As if its done properly fills in the missing blanks in how this
    formula or that derived.

    Thus far the list above narrows down which of the multitude of inflation model alternatives to further study
    Last edited: Apr 27, 2013
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