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

Quantum gravity in astrophysics?

  1. Feb 4, 2013 #1
    I'm currently taking an astrophysics course, and need to do a project on some sort of on-going astrophysics research. Over the last year, I've been reading a few papers here and there in QG (specifically LQG), and was wondering if there was any on-going research relating quantum gravity in astrophysics??

    Some problems I know of are fluctuations of the metric, but uh, don't know if that has ANY applicability in astrophysics as I'm pretty naive when it comes to this field.

    Thanks for any help!
  2. jcsd
  3. Feb 4, 2013 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Ashtekar is a big name in QG (specifically LQG) and his focus is on the application of LQG to cosmology. He and two younger co-authors just came out with a major paper this month. It would have references to earlier related work.

    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
  4. Feb 4, 2013 #3


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    I was too busy and didn't get you a suitable bunch of suggestions. That paper may be too technical. I'll try to think how to get some papers relating QG and astrophysics which span a range of difficulty.

    This list has some great papers but the link is slow. It might take 10 seconds. If it times out just click on it again.

    It is a search specialized to find research that appeared 2009 or later exploring ways of TESTING quantum cosmology (phenomenology, comparing QG cosmology models with observation.)
    http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+LOOP+SPACE+AND+%28QUANTUM+GRAVITY+OR+QUANTUM+COSMOLOGY%29+%29+AND+%28GRAVITATIONAL+RADIATION+OR+PRIMORDIAL+OR+inflation+or+POWER+SPECTRUM+OR+COSMIC+BACKGROUND+RADIATION%29+AND+DATE%3E2008&FORMAT=www&SEQUENCE=citecount%28d%29 [Broken]
    I just tested it and it took over 20 seconds but at least did not time out, and came up with 69 papers.
    For example the top one on the list was:

    1) Cosmological footprints of loop quantum gravity.
    J. Grain, (APC, Paris & Paris, Inst. Astrophys.) , A. Barrau, (LPSC, Grenoble & IHES, Bures-sur-Yvette) . Feb 2009. (Published Feb 27, 2009). 7pp.
    Published in Phys.Rev.Lett.102:081301,2009.
    e-Print: http://arxiv.org/abs/0902.0145 [gr-qc]
    TOPCITE = 50+
    Cited 50 times

    Aurelien Barrau has written many papers relating QG to observational early universe cosmology, effects to look for in the CMB (microwave background, the most ancient light we can observe0

    Also Julien Grain has written a lot. You can look his up too. There are more recent papers than what i mentioned.
    Last edited by a moderator: May 6, 2017
  5. Feb 6, 2013 #4
    Thanks for your help! I'll take a look at the papers you posted. And will also see what Julien Grain has written!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook