33 research outputs found
Primordial Entropy Production and Lambda-driven Inflation from Quantum Einstein Gravity
We review recent work on renormalization group (RG) improved cosmologies
based upon a RG trajectory of Quantum Einstein Gravity (QEG) with realistic
parameter values. In particular we argue that QEG effects can account for the
entire entropy of the present Universe in the massless sector and give rise to
a phase of inflationary expansion. This phase is a pure quantum effect and
requires no classical inflaton field.Comment: 12 pages, 4 figures, IGCG-07 Pun
Multi-field Inflation with a Random Potential
Motivated by the possibility of inflation in the cosmic landscape, which may
be approximated by a complicated potential, we study the density perturbations
in multi-field inflation with a random potential. The random potential causes
the inflaton to undergo a Brownian motion with a drift in the D-dimensional
field space. To quantify such an effect, we employ a stochastic approach to
evaluate the two-point and three-point functions of primordial perturbations.
We find that in the weakly random scenario the resulting power spectrum
resembles that of the single field slow-roll case, with up to 2% more red tilt.
The strongly random scenario, leads to rich phenomenologies, such as primordial
fluctuations in the power spectrum on all angular scales. Such features may
already be hiding in the error bars of observed CMB TT (as well as TE and EE)
power spectrum and can be detected or falsified with more data coming in the
future. The tensor power spectrum itself is free of fluctuations and the tensor
to scalar ratio is enhanced. In addition a large negative running of the power
spectral index is possible. Non-Gaussianity is generically suppressed by the
growth of adiabatic perturbations on super-horizon scales, but can possibly be
enhanced by resonant effects or arise from the entropic perturbations during
the onset of (p)reheating. The formalism developed in this paper can be applied
to a wide class of multi-field inflation models including, e.g. the N-flation
scenario.Comment: More clarifications and references adde
Multi-field Inflation with a Random Potential
Motivated by the possibility of inflation in the cosmic landscape, which may
be approximated by a complicated potential, we study the density perturbations
in multi-field inflation with a random potential. The random potential causes
the inflaton to undergo a Brownian motion with a drift in the D-dimensional
field space. To quantify such an effect, we employ a stochastic approach to
evaluate the two-point and three-point functions of primordial perturbations.
We find that in the weakly random scenario the resulting power spectrum
resembles that of the single field slow-roll case, with up to 2% more red tilt.
The strongly random scenario, leads to rich phenomenologies, such as primordial
fluctuations in the power spectrum on all angular scales. Such features may
already be hiding in the error bars of observed CMB TT (as well as TE and EE)
power spectrum and can be detected or falsified with more data coming in the
future. The tensor power spectrum itself is free of fluctuations and the tensor
to scalar ratio is enhanced. In addition a large negative running of the power
spectral index is possible. Non-Gaussianity is generically suppressed by the
growth of adiabatic perturbations on super-horizon scales, but can possibly be
enhanced by resonant effects or arise from the entropic perturbations during
the onset of (p)reheating. The formalism developed in this paper can be applied
to a wide class of multi-field inflation models including, e.g. the N-flation
scenario.Comment: More clarifications and references adde