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main page: InvisibleUniverse2009**These are just rough notes - feel free to correct them, add links, etc.** from the Invisible Universe 28 June - 3 July 2009 meeting. These are **not** official proceedings. The speakers might even disagree that they said anything even vaguely related to what are in these online notes! Don't say you weren't warned.
# Abhay Ashtekar

loop quantum cosmology = LQC vs WDW = Wheeler de Witt

main page: InvisibleUniverse2009

- ArXiv:0812.0177 - recommended review paper
- WDW quantum cosmology not mathematically rigorous
- since 1970's worry about von Neumann uniqueness theorem * LQC is rigorous

- LQC solves these problems BoudRoukema - 03 Jul 2009
- LQC - quantum geometry - gives repulsive force during planck epoch, i.e. a bounce
- "quantum geometry resolves
**all**strong singularities in homogeneous isotropic models with ... (Singh) - k=1 models bounce at 't=0', i.e. avoid singularity (Ashtekar, Pawlowski, ...)
- BKL conjecture: approaching Planck era, dynamics well approximated by Bianchi I models, with Bianchi II transitions and spikes
- LQC also resolves singularities in Bianchi I, II models

- in LQG, there may be a general
**singularity resolution theorem** - phenomenology - work in progress
- super-inflation - Copeland et al
- do inflation calculations using LQC-corrected Einstein eqns
- horizon and flatness problems solved by super-inflation
- nearly scale invariant spectrum for scalar mode
- ...

- evolution of perturbations from pre-BB to post-BB branch
- Biswas working on this

- all this is very much work in progress by LQC community

- summary:
- QG gives quantum bounce
- physics does not end at singularities
- classical GR at low curvatures/densities (Green and Unruh)
- the singularities analysed here are those of direct cosmological interest (not just abstract singularities!)
- phenomeology - initial results obtained, cosmologists and LQC communities working together on this

This topic: Cosmo > WebPreferences > WebHome > InvisibleUniverse2009 > InvUniv2009Ashtekar

Topic revision: 03 Jul 2009, BoudRoukema

Topic revision: 03 Jul 2009, BoudRoukema

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