Observational constraints of a power spectrum from superinflation in loop quantum cosmology

Shimano, Masahiro; Harada, Tomohiro

doi:10.1103/physrevd.80.063538

Cited by 28 publications

(12 citation statements)

References 33 publications

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“…Inverse volume corrections and cosmological perturbations: Because these corrections are simplest to study in the context of perturbations in LQC, there is a large body of literature on the subject for both scalar and tensor perturbations (see e.g. [68,205,[238][239][240][241][242]). These investigations have been carried out under a variety of scenarios: approximating the asymptotic region in deep Planck regime by a particular variation of the scale factor [239]; considering various values of j labeling representations of SU(2) used to compute the inverse volume corrections [241]; etc.…”

Section: Lqc Corrections To Standard Paradigmsmentioning

confidence: 99%

Loop quantum cosmology: a status report

Ashtekar¹,

Singh²

2011

Class. Quantum Grav.

1,060

1,741

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Loop quantum cosmology (LQC) is the result of applying principles of loop quantum gravity (LQG) to cosmological settings. The distinguishing feature of LQC is the prominent role played by the quantum geometry effects of LQG. In particular, quantum geometry creates a brand new repulsive force which is totally negligible at low space-time curvature but rises very rapidly in the Planck regime, overwhelming the classical gravitational attraction. In cosmological models, while Einstein's equations hold to an excellent degree of approximation at low curvature, they undergo major modifications in the Planck regime: For matter satisfying the usual energy conditions any time a curvature invariant grows to the Planck scale, quantum geometry effects dilute it, thereby resolving singularities of general relativity. Quantum geometry corrections become more sophisticated as the models become richer. In particular, in anisotropic models there are significant changes in the dynamics of shear potentials which tame their singular behavior in striking contrast to older results on anisotropies in bouncing models. Once singularities are resolved, the conceptual paradigm of cosmology changes and one has to revisit many of the standard issues -e.g., the 'horizon problem'-from a new perspective. Such conceptual issues as well as potential observational consequences of the new Planck scale physics are being explored, especially within the inflationary paradigm. These considerations have given rise to a burst of activity in LQC in recent years, with contributions from quantum gravity experts, mathematical physicists and cosmologists.The goal of this article is to provide an overview of the current state of the art in LQC for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general; and, cosmologists who wish to apply LQC to probe modifications in the standard paradigm of the early universe. An effort has been made to streamline the material so that each of these communities can read only the sections they are most interested in, without a loss of continuity. * Electronic address: ashtekar@gravity.psu.edu † Electronic address: psingh@phys.lsu.eduAs before, C H and the symplectic structure are insensitive to the choice ofq ab but they do

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Section: Lqc Corrections To Standard Paradigmsmentioning

confidence: 99%

Loop quantum cosmology: a status report

Ashtekar¹,

Singh²

2011

Class. Quantum Grav.

1,060

1,741

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“…The cancellation of anomalies is obtained by introducing counterterms. After some early works based on toy models where the constraint algebra was not explicitly closed [53,54,55,56,57,58,59], the full set of constraints with small inverse-volume corrections was derived for vector [34], tensor [29], and scalar modes [60,61]. The associated gravitational wave spectrum was studied in [46,62,63], while the scalar spectrum and the full set of linear-order cosmological observables were found in [48].…”

Section: Perturbations With Inverse Volume Correctionsmentioning

confidence: 99%

Observational issues in loop quantum cosmology

Barrau¹,

Cailleteau²,

Grain³

et al. 2014

Class. Quantum Grav.

117

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Abstract. Quantum gravity is sometimes considered as a kind of metaphysical speculation. In this review, we show that, although still extremely difficult to reach, observational signatures can in fact be expected. The early universe is an invaluable laboratory to probe "Planck scale physics". Focusing on Loop Quantum Gravity as one of the best candidate for a non-perturbative and background-independant quantization of gravity, we detail some expected features.Invited topical review for Classical and Quantum Gravity.

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“…The evolution of V is given by Eq. (27) and, in particular, the bounce is given by dV d ¼ 0 which gives, Re Jj Bounce ¼ 0:…”

Section: A Zero Potentialmentioning

confidence: 99%

“…In particular, because Eq. (27) and the equations in Appendix A are flows in configuration space (i.e. depend explicitly only on the variables and not their derivatives) the numerical implementation is rather straightforward.…”

Section: Numerical Evolution Of the Systemmentioning

confidence: 99%

High-density regime of kinetic-dominated loop quantum cosmology

et al. 2010

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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.

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Observational constraints of a power spectrum from superinflation in loop quantum cosmology

Cited by 28 publications

References 33 publications

Loop quantum cosmology: a status report

Loop quantum cosmology: a status report

Observational issues in loop quantum cosmology

High-density regime of kinetic-dominated loop quantum cosmology

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