7 research outputs found
Perturbations in loop quantum cosmology
The era of precision cosmology has allowed us to accurately determine many important cosmological parameters, in particular via the CMB. Confronting Loop Quantum Cosmology with these observations provides us with a powerful test of the theory. For this to be possible, we need a detailed understanding of the generation and evolution of inhomogeneous perturbations during the early, quantum gravity phase of the universe. Here, we have described how Loop Quantum Cosmology provides a completion of the inflationary paradigm, that is consistent with the observed power spectra of the CMB. © Published under licence by IOP Publishing Ltd
Numerical loop quantum cosmology: an overview
A brief review of various numerical techniques used in loop quantum cosmology
and results is presented. These include the way extensive numerical simulations
shed insights on the resolution of classical singularities, resulting in the
key prediction of the bounce at the Planck scale in different models, and the
numerical methods used to analyze the properties of the quantum difference
operator and the von Neumann stability issues. Using the quantization of a
massless scalar field in an isotropic spacetime as a template, an attempt is
made to highlight the complementarity of different methods to gain
understanding of the new physics emerging from the quantum theory. Open
directions which need to be explored with more refined numerical methods are
discussed.Comment: 33 Pages, 4 figures. Invited contribution to appear in Classical and
Quantum Gravity special issue on Non-Astrophysical Numerical Relativit
Loop Quantum Cosmology: A Status Report
The goal of this article is to provide an overview of the current state of
the art in loop quantum cosmology for three sets of audiences: young
researchers interested in entering this area; the quantum gravity community in
general; and, cosmologists who wish to apply loop quantum cosmology to probe
modifications in the standard paradigm of the early universe. An effort has
been made to streamline the material so that, as described at the end of
section I, each of these communities can read only the sections they are most
interested in, without a loss of continuity.Comment: 138 pages, 15 figures. Invited Topical Review, To appear in Classical
and Quantum Gravity. Typos corrected, clarifications and references adde
The pre-inflationary dynamics of loop quantum cosmology: confronting quantum gravity with observations
Contains fulltext :
111281.pdf (preprint version ) (Open Access
Holonomy corrections in the effective equations for scalar mode perturbations in loop quantum cosmology
A quantum gravitational inflationary scenario in Bianchi-I spacetime
We investigate the inflationary model in the Bianchi-I spacetime
using effective spacetime description of loop quantum cosmology to understand
the issues of the resolution of initial singularity, isotropization, effect of
anisotropies on amount of inflation, and the phase space attractors in the
presence of non-perturbative quantum gravitational modifications. A comparative
analysis with the classical theory by including more general initial conditions
than the ones previously considered in the latter is also performed. We show
that, in general, the classical singularity is replaced by a bounce of the mean
scale factor in loop quantum cosmology. Due to the underlying quantum geometric
effects, the energy density of the inflaton and the anisotropic shear remain
bounded throughout the non-singular evolution. Starting from arbitrary
anisotropic initial conditions, a loop quantum universe isotropizes either
before or soon after the onset of slow-roll inflation. We find a double
attractor behavior in the phase space dynamics of loop quantum cosmology,
similar to the one in classical theory, but with some additional subtle
features. Quantum modifications to the dynamical equations are such that,
unlike the classical theory, the amount of inflation does not monotonically
depend on the initial anisotropy in loop quantum cosmology. Our results suggest
that a viable non-singular inflationary model can be constructed from highly
anisotropic initial conditions in the Planck regime.Comment: 35 pages, 19 figures. References added. Minor changes to match
published version. To appear in CQ