Robustness of key features of loop quantum cosmology
Abstract
A small simplification based on wellmotivated approximations is shown to make loop quantum cosmology of the k=0 FriedmanRobertsonWalker model (with a massless scalar field) exactly soluble. Analytical methods are then used i) to show that the quantum bounce is generic; ii) to establish that the matter density has an absolute upper bound which, furthermore, equals the critical density that first emerged in numerical simulations and effective equations; iii) to bring out the precise sense in which the WheelerDeWitt theory approximates loop quantum cosmology and the sense in which this approximation fails; and iv) to show that discreteness underlying loop quantum cosmology is fundamental. Finally, the model is compared to analogous discussions in the literature and it is pointed out that some of their expectations do not survive a more careful examination. An effort has been made to make the underlying structure transparent also to those who are not familiar with details of loop quantum gravity.
 Publication:

Physical Review D
 Pub Date:
 January 2008
 DOI:
 10.1103/PhysRevD.77.024046
 arXiv:
 arXiv:0710.3565
 Bibcode:
 2008PhRvD..77b4046A
 Keywords:

 04.60.Pp;
 04.60.Ds;
 04.60.Nc;
 11.10.Gh;
 Loop quantum gravity quantum geometry spin foams;
 Canonical quantization;
 Lattice and discrete methods;
 Renormalization;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 Two changes from the published version: (1) Use of the scalar field clock already in the classical theory leads to a soluble model without any assumptions. sLQC now stands for soluble (rather than simplified) LQC