Editing Loop quantum gravity (section)

=== Loop quantum cosmology ===
{{main|Loop quantum cosmology|Big bounce|inflation (cosmology)}}
The popular and technical literature makes extensive references to the LQG-related topic of loop quantum cosmology. LQC was mainly developed by Martin Bojowald. It was popularized in ''[[Scientific American]]'' for predicting a [[Big Bounce]] prior to the [[Big Bang]].{{sfn|Bojowald|2008}} Loop quantum cosmology (LQC) is a symmetry-reduced model of classical general relativity quantized using methods that mimic those of loop quantum gravity (LQG) that predicts a "quantum bridge" between contracting and expanding cosmological branches.

Achievements of LQC have been the resolution of the big bang [[Singularity (mathematics)|singularity]], the prediction of a Big Bounce, and a natural mechanism for [[inflation (cosmology)|inflation]].

LQC models share features of LQG and so is a useful toy model. However, the results obtained are subject to the usual restriction that a truncated classical theory, then quantized, might not display the true behaviour of the full theory due to artificial suppression of degrees of freedom that might have large quantum fluctuations in the full theory. It has been argued that singularity avoidance in LQC are by mechanisms only available in these restrictive models and that singularity avoidance in the full theory can still be obtained but by a more subtle feature of LQG.{{sfn|Brunnemann|Thiemann|2006a|pp=1395–1428}}{{sfn|Brunnemann|Thiemann|2006b|pp=1429–1484}}