title: Singularities in loop quantum cosmology.
abstract: We show that simple scalar field models can give rise to curvature singularities in the effective Friedmann dynamics of loop quantum cosmology (LQC). We find singular solutions for spatially flat Friedmann-Robertson-Walker cosmologies with a canonical scalar field and a negative exponential potential, or with a phantom scalar field and a positive potential. While LQC avoids big bang or big rip type singularities, we find sudden singularities where the Hubble rate is bounded, but the Ricci curvature scalar diverges. We conclude that the effective equations of LQC are not in themselves sufficient to avoid the occurrence of curvature singularities.
authors.affiliation: Physique Fondamentale et appliquée, Universite Paris-Sud 11, 91405 Orsay Cedex, France. thomas.cailleteau@gmail.com
authors.forename: Thomas
authors.initials: T
authors.lastname: Cailleteau
authors.forename: Antonio
authors.initials: A
authors.lastname: Cardoso
authors.forename: Kevin
authors.initials: K
authors.lastname: Vandersloot
authors.forename: David
authors.initials: D
authors.lastname: Wands