Jakub Mielczarek

Gravitational waves from the big?bounce

In this paper we investigate gravitational wave production during the big bounce phase, inspired by loop quantum cosmology. We consider the influence of the holonomy corrections to the equation for tensor modes. We show that they act like additional effective graviton mass, suppressing gravitational wave creation. However, such effects can be treated perturbatively. We investigate a simplified model without holonomy corrections to the equation for modes and find its exact analytical solution. Assuming the form for matter we calculate the full spectrum of the gravitational waves from the big bounce phase. The spectrum obtained decreases to zero for the low energy modes. On the basis of this observation we infer that this effect can lead to low cosmic microwave background (CMB) multipole suppression and gives a potential way for testing loop quantum cosmology models. We also consider a scenario with a post-bounce inflationary phase. The power spectrum obtained gives a qualitative explanation of the CMB spectra, including low multipole suppression.

Observational issues in loop quantum cosmology

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-independent quantization of gravity, we detail some expected features.

Possible observational effects of loop quantum cosmology

In this paper, we consider realistic model of inflation embedded in the framework of loop quantum cosmology. Phase of inflation is preceded here by the phase of a quantum bounce. We show how parameters of inflation depend on the initial conditions established in the contracting, prebounce phase. Our investigations indicate that phase of the bounce easily sets proper initial conditions for the inflation. Subsequently, we study observational effects that might arise due to the quantum gravitational modifications. We perform preliminary observational constraints for the Barbero-Immirzi parameter

Some implications of signature-change in cosmological models of loop quantum gravity

\ensuremath{\gamma}

Reheating temperature from the CMB

, critical density

Tensor power spectrum with holonomy corrections in loop quantum cosmology

{\ensuremath{\rho}}_{\mathrm{c}}

Asymptotic silence in loop quantum cosmology

, and parameter

Relic gravitons as the observable for loop quantum cosmology

\ensuremath{\lambda}

Primordial scalar power spectrum from the Euclidean Big Bounce

. In the next step, we study effects on power spectrum of perturbations. We calculate spectrum of perturbations from the bounce and from the joined

Inflationary power spectra with quantum holonomy corrections

\mathrm{\text{bounce}}+\mathrm{\text{inflation}}