High-density regime of kinetic-dominated loop quantum cosmology

M. Bojowald, W. Nelson, D. Mulryne, R. Tavakol

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We study the dynamics of states perturbatively expanded about a harmonic system of loop quantum cosmology, exhibiting a bounce. In particular, the evolution equations for the first and second-order moments of the system are analyzed. These moments back-react on the trajectories of the expectation values of the state and hence alter the energy density at the bounce. This analysis is performed for isotropic loop quantum cosmology coupled to a scalar field with a small but nonzero constant potential, hence in a regime in which the kinetic energy of matter dominates. Analytic restrictions on the existence of dynamical coherent states and the meaning of semiclassicality within these systems are discussed. A numerical investigation of the trajectories of states that remain semiclassical across the bounce demonstrates that, at least for such states, the bounce persists and that its properties are similar to the standard case, in which the moments of the states are entirely neglected. However, the bounce density does change, implying that a quantum bounce may not be guaranteed to happen when the potential is no longer negligible.

Original languageEnglish (US)
Article number124055
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number12
StatePublished - 2010

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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