The dispersion of growth of matter perturbations in f(R) gravity (2009)
Tsujikawa, Shinji, Gannouji, Radouane, Moraes, Bruno, Polarski, David
We study the growth of matter density perturbations delta_m for a number of viable f(R) gravity models that satisfy both cosmological and local gravity constraints, where the Lagrangian density f is...
Dispersion in the growth of matter perturbations (2009)
Gannouji, Radouane, Moraes, Bruno, Polarski, David
We consider the linear growth of matter perturbations on low redshifts in modified gravity Dark Energy (DE) models where G_eff(z,k) is explicitly scale-dependent. Dispersion in the growth today will...
Why do cosmological perturbations look classical to us? (2008)
Kiefer, Claus, Polarski, David
According to the inflationary scenario of cosmology, all structure in the Universe can be traced back to primordial fluctuations during an accelerated (inflationary) phase of the very early Universe....
The growth of matter perturbations in some scalar-tensor DE models (2008)
Gannouji, Radouane, Polarski, David
We consider asymptotically stable scalar-tensor dark energy (DE) models for which the equation of state parameter $w_{DE}$ tends to zero in the past. The viable models are of the phantom type today,...
The Growth of Density Fluctuations in a Simplified Model of Extended Inflation (2007)
Nathalie Deruelle Carsten, Carsten Gundlach, David Polarski
We reduce the cosmological model of extended inflation to a spatially flat RobertsonWalker geometry driven by a self-interacting scalar field with a potential of an exponential type. We quantize the...
On the growth of linear perturbations (2007)
Polarski, David, Gannouji, Radouane
We consider the linear growth of matter perturbations in various dark energy (DE) models. We show the existence of a constraint valid at $z=0$ between the background and dark energy parameters and...
Conditions for the cosmological viability of f(R) dark energy models (2006)
Amendola, Luca, Gannouji, Radouane, Polarski, David, Tsujikawa, Shinji
We derive the conditions under which dark energy models whose Lagrangian densities f are written in terms of the Ricci scalar R are cosmologically viable. We show that the cosmological behavior of...
Scalar-Tensor Models of Normal and Phantom Dark Energy (2006)
Gannouji, Radouane, Polarski, David, Ranquet, Andre, Starobinsky, Alexei A.
We consider the viability of dark energy (DE) models in the framework of the scalar-tensor theory of gravity, including the possibility to have a phantom DE at small redshifts $z$ as admitted by...
Power-laws f(R) theories are cosmologically unacceptable (2006)
Amendola, Luca, Polarski, David, Tsujikawa, Shinji
In a recent paper [1] (PRL 98,131302,2007) we have shown that f(R)=R + mu R^{n} modified gravity dark energy models are not cosmologically viable because during the matter era that precedes the...
Are f(R) dark energy models cosmologically viable ? (2006)
Amendola, Luca, Polarski, David, Tsujikawa, Shinji
All $f(R)$ modified gravity theories are conformally identical to models of quintessence in which matter is coupled to dark energy with a strong coupling. This coupling induces a cosmological...
Can Primordial Black Holes be a Significant Part of Dark Matter ? (2005)
Blais, David, Kiefer, Claus, Polarski, David
The computation of PBH (primordial black hole) production from primordial perturbations has recently been improved by considering a more accurate relation between the primordial power spectrum and...
Can Lightcone Fluctuations be Probed with Cosmological Backgrounds? (2005)
Polarski, David, Roche, Philippe
Finding signatures of quantum gravity in cosmological observations is now actively pursued both from the theoretical and the experimental side. Recent work has concentrated on finding signatures of...
Accurate results for primordial black holes from spectra with a distinguished scale (2002)
Blais, David, Bringmann, Torsten, Kiefer, Claus, Polarski, David
We perform an accurate computation of the production rate for primordial black holes (PBHs). The reason is that the underlying mass variance had been overestimated systematically, as was shown...
Can Primordial Black Holes be a Significant Part of Dark Matter ? (2002)
Blais, David, Kiefer, Claus, Polarski, David
The computation of PBH (primordial black hole) production from primordial perturbations has recently been improved by considering a more accurate relation between the primordial power spectrum and...
Can Primordial Black Holes be a Significant Part of Dark Matter ? (2002)
Blais, David, Kiefer, Claus, Polarski, David
The computation of PBH (primordial black hole) production from primordial perturbations has recently been improved by considering a more accurate relation between the primordial power spectrum and...
Can Primordial Black Holes be a Significant Part of Dark Matter ? (2002)
Blais, David, Kiefer, Claus, Polarski, David
The computation of PBH (primordial black hole) production from primordial perturbations has recently been improved by considering a more accurate relation between the primordial power spectrum and...
Primordial Black Holes in an Accelerating Universe (2001)
General expressions are given for the generation of Primordial Black Holes (PBH) in a universe with a presently accelerated expansion due to a(n effective) cosmological constant. We give expressions...
Primordial Black Holes from inflationary models with and without Broken Scale Invariance (2001)
Bringmann, Torsten, Kiefer, Claus, Polarski, David
We review the formalism of primordial black holes (PBHs) production and show that the mass variance at horizon crossing has been systematically overestimated in previous studies. We derive the...
Classicality of primordial fluctuations and Primordial Black Holes (2001)
The production of Primordial Black Holes (PBH) from inflationary perturbations provides a physical process where the effective classicality of the fluctuations does not hold for certain scales. For...
Accelerated Expansion: Theory and Observations (2001)
The present paradigm in cosmology is the usual Big-Bang Cosmology in which two stages of accelerated expansion are incorporated: the inflationary phase in the very early universe which produces the...
Detectability of the primordial origin of the gravitational wave background in the Universe (1999)
Lesgourgues, Julien, Polarski, David, Prunet, Simon, Starobinski, A. A.
The appearance of peaks in the Fourier power spectra of various primordial fluctuations is a generic prediction of the inflationary scenario. We investigate whether future experiments, in particular...
Large primordial gravitational wave background in a class of BSL ACDM models (1999)
Lesgourgues, Julien, Polarski, David, Starobinsky, A.A.
We consider the primordial gravitational wave (GW) background in a class of spatially-flat inflationary cosmological models with cold dark matter (CDM), a cosmological constant, and a...
Lesgourgues, Julien, Prunet, Simon, Polarski, David
We consider a class of spatially flat cold dark matter (CDM) models, with a cosmological constant and a broken-scale-invariant (BSI) steplike primordial spectrum of adiabatic perturbations,...
Primordial Fluctuations from Inflation: a Consistent Histories Approach (1998)
We show how the quantum-to-classical transition of the cosmological fluctuations produced during an inflationary stage can be described using the consistent histories approach. We identify the...
On the Phase-Space Volume of Primordial Cosmological Perturbations (1998)
Lesgourgues, Julien, Polarski, David, Starobinsky, Alexei A.
We show how to determine the typical phase space volume $\Gamma$ for primordial gravitational waves produced during an inflationary stage, which is invariant under squeezing. An expression for...
The Coherence of Primordial Fluctuations Produced During Inflation (1998)
Kiefer, Claus, Lesgourgues, Julien, Polarski, David, Starobinsky, Alexei A.
The behaviour of quantum metric perturbations produced during inflation is considered at the stage after the second Hubble radius crossing. It is shown that the classical correlation between...
CMB anisotropy predictions for a model of double inflation (1997)
Lesgourgues, Julien, Polarski, David
We consider a double-inflationary model with two massive scalar fields interacting only gravitationally in the context of a flat cold dark matter (CDM) Universe. The cosmic microwave background (CMB)...
Quantum-to-classical Transition of Cosmological Perturbations for Non-vacuum Initial States (1996)
Lesgourgues, Julien, Polarski, David, Starobinsky, Alexei A.
Transition from quantum to semiclassical behaviour and loss of quantum coherence for inhomogeneous perturbations generated from a non-vacuum initial state in the early Universe is considered in the...
Structure of Primordial Gravitational Waves Spectrum in a Double Inflationary Model (1995)
Polarski, David, Starobinsky, Alexei A.
The gravitational waves (GW) background generated in a double inflationary model, with two scalar fields mutually interacting through gravity only, and its relative contribution $T/S$ to large-angle...
Semiclassicality and Decoherence of Cosmological Perturbations (1995)
Polarski, David, Starobinsky, Alexei A.
Transition to the semiclassical behaviour and the decoherence process for inhomogeneous perturbations generated from the vacuum state during an inflationary stage in the early Universe are considered...
On The Quantisation Of Perturbations In Inflation (1991)
Nathalie Deruelle, Carsten Gundlach, David Polarski
The theory of gauge-invariant scalar perturbations in chaotic inflation is briefly reviewed. We clarify a problem related to their quantisation, pertinent to any inflationary model. 1 1. Introduction...