Search Publications
Inflation and dark energy from the Brans-Dicke theory
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek
We consider the Brans-Dicke theory motivated by the f(R) = R + α Rn - β R2-n model to obtain a stable minimum of the Einstein frame scalar potential of the Brans-Dicke field. As a result we have obtained an inflationary scalar potential with non-zero value of residual vacuum energy, which may be a source of dark energy. In ad…
Joint Planck and WMAP assessment of low CMB multipoles
Souradeep, Tarun; Prasad, Jayanti; Iqbal, Asif +1 more
The remarkable progress in cosmic microwave background (CMB) studies over past decade has led to the era of precision cosmology in striking agreement with the ΛCDM model. However, the lack of power in the CMB temperature anisotropies at large angular scales (low-ℓ), as has been confirmed by the recent Planck data also (up to 0ℓ=4), although statis…
Constraining dark sector perturbations I: cosmic shear and CMB lensing
Battye, Richard A.; Moss, Adam; Pearson, Jonathan A.
We present current and future constraints on equations of state for dark sector perturbations. The equations of state considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant ℒ(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. We de…
A non-minimally coupled potential for inflation and dark energy after Planck 2015: a comprehensive study
Eshaghi, Mehdi; Zarei, Moslem; Riazi, Nematollah +1 more
In this work we introduce a new plateau-like inflationary model including a quadratic scalar potential coupled non-minimally to gravity. This potential has a dominant constant energy density at early times which can realize successful inflation. It also includes an infinitesimal non-zero term V0 responsible for explaining dark energy wh…
Bayesian evidence of the post-Planck curvaton
Byrnes, Christian T.; Hardwick, Robert J.
We perform a Bayesian model comparison for scenarios within the quadratic curvaton model, determining the degree to which both are disfavoured with respect to the ΛCDM concordance model and single-field quadratic inflation, using the recent Planck data release. Despite having three additional model parameters, the simplest curvaton scenario is not…
Negative running can prevent eternal inflation
Kinney, William H.; Freese, Katherine
Current data from the Planck satellite and the BICEP2 telescope favor, at around the 2 σ level, negative running of the spectral index of curvature perturbations from inflation. We show that for negative running α < 0, the curvature perturbation amplitude has a maximum on scales larger than our current horizon size. A condition for the absence …
Extragalactic sources in Cosmic Microwave Background maps
Andreani, P.; Bonavera, L.; Clements, D. L. +15 more
We discuss the potential of a next generation space-borne CMB experiment for studies of extragalactic sources with reference to COrE+, a project submitted to ESA in response to the call for a Medium-size mission (M4). We consider three possible options for the telescope size: 1 m, 1.5 m and 2 m (although the last option is probably impractical, gi…
Constraining dark sector perturbations II: ISW and CMB lensing tomography
Weller, J.; Giannantonio, T.; Battye, R. A. +1 more
Any Dark Energy (DE) or Modified Gravity (MG) model that deviates from a cosmological constant requires a consistent treatment of its perturbations, which can be described in terms of an effective entropy perturbation and an anisotropic stress. We have considered a recently proposed generic parameterisation of DE/MG perturbations and compared it t…
The Kullback-Leibler divergence as an estimator of the statistical properties of CMB maps
Liu, Hao; Ben-David, Assaf; Jackson, Andrew D.
The identification of unsubtracted foreground residuals in the cosmic microwave background maps on large scales is of crucial importance for the analysis of polarization signals. These residuals add a non-Gaussian contribution to the data. We propose the Kullback-Leibler (KL) divergence as an effective, non-parametric test on the one-point probabi…
How CMB and large-scale structure constrain chameleon interacting dark energy
Wong, Yvonne Y. Y.; Boriero, Daniel; Das, Subinoy
We explore a chameleon type of interacting dark matter-dark energy scenario in which a scalar field adiabatically traces the minimum of an effective potential sourced by the dark matter density. We discuss extensively the effect of this coupling on cosmological observables, especially the parameter degeneracies expected to arise between the model …