B-mode Detection with an Extended Planck Mission (2009)
Efstathiou, George, Gratton, Steven
The Planck satellite has a nominal mission lifetime of 14 months allowing two complete surveys of the sky. Here we investigate the potential of an extended Planck mission of four sky surveys to...
Impact of Galactic polarized emission on B-mode detection at low multipoles (2009)
Efstathiou, George, Gratton, Steven, Paci, Francesco
We use a model of polarized Galactic emission developed by the the Planck collaboration to assess the impact of foregrounds on B-mode detection at low multipoles. Our main interest is to applications...
Prescription for Cosmic Information Extraction from Multiple Sky Maps (2008)
This paper presents a prescription for distilling the information contained in the cosmic microwave background radiation from multiple sky maps that also contain both instrument noise and foreground...
Prospects for Constraining Neutrino Mass Using Planck and Lyman-Alpha Forest Data (2007)
Gratton, Steven, Lewis, Antony, Efstathiou, George
In this paper we investigate how well Planck and Lyman-Alpha forest data will be able to constrain the sum of the neutrino masses, and thus, in conjunction with flavour oscillation experiments, be...
Measures on transitions for cosmology from eternal inflation (2006)
Aguirre, Anthony, Gratton, Steven, Johnson, Matthew C
We argue that in the context of eternal inflation in the landscape, making predictions for cosmological -- and possibly particle physics -- observables requires a measure on the possible cosmological...
Hurdles for Recent Measures in Eternal Inflation (2006)
Aguirre, Anthony, Gratton, Steven, Johnson, Matthew C
In recent literature on eternal inflation, a number of measures have been introduced which attempt to assign probabilities to different pocket universes by counting the number of each type of pocket...
Cosmic Perturbations Through the Cyclic Ages (2006)
Erickson, Joel K., Gratton, Steven, Steinhardt, Paul J., Turok, Neil
We analyze the evolution of cosmological perturbations in the cyclic model, paying particular attention to their behavior and interplay over multiple cycles. Our key results are: (1) galaxies and...
Langevin Analysis of Eternal Inflation (2005)
It has been widely claimed that inflation is generically eternal to the future, even in models where the inflaton potential monotonically increases away from its minimum. The idea is that quantum...
Conditions for Generating Scale-Invariant Density Perturbations (2003)
Gratton, Steven, Khoury, Justin, Steinhardt, Paul J., Turok, Neil
We analyze the general conditions on the equation of state $w$ required for quantum fluctuations of a scalar field to produce a scale-invariant spectrum of density perturbations, including models...
Inflation without a beginning: a null boundary proposal (2003)
Aguirre, Anthony, Gratton, Steven
We develop our recent suggestion that inflation may be made past eternal, so that there is no initial cosmological singularity or "beginning of time". Inflation with multiple vacua generically...
Steady-State Eternal Inflation (2001)
Aguirre, Anthony, Gratton, Steven
Since the advent of inflation, several theorems have been proven suggesting that although inflation can (and generically does) continue eternally into the future, it cannot be extended eternally into...
Closed Universes from Cosmological Instantons (2001)
Gratton, Steven, Lewis, Antony, Turok, Neil
Current observational data is consistent with the universe being slightly closed. We investigate families of singular and non-singular closed instantons that could describe the beginning of a closed...
Homogeneous Modes of Cosmological Instantons (2000)
We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their...
An Observational Test of Quantum Cosmology (1999)
Gratton, Steven, Hertog, Thomas, Turok, Neil
We compute the tensor CMB anisotropy power spectrum for singular and non-singular instantons describing the beginning of an open universe according to the Euclidean no boundary proposal. Singular...
Cosmological Perturbations from the No Boundary Euclidean Path Integral (1999)
We compute, from first principles, the quantum fluctuations about instanton saddle points of the Euclidean path integral for Einstein gravity coupled to a scalar field. The Euclidean two-point...