Licia Verde

Constraints on the redshift dependence of the dark energy potential

We develop a formalism to characterize the shape and the redshift evolution of the dark energy potential. Our formalism makes use of quantities similar to the horizon-flow parameters in inflation and is general enough that can deal with multiscalar quintessence scenarios, exotic matter components, and higher-order curvature corrections to General Relativity. We show how the shape of the dark energy potential can be recovered nonparametrically using this formalism and we present approximations analogous to the ones relevant to slow-roll inflation. Since presently available data do not allow a nonparametric and exact reconstruction of the potential, we consider a general parametric description. This reconstruction can also be used in other approaches followed in the literature (e.g., the reconstruction of the redshift evolution of the dark energy equation of state

On model selection forecasting, Dark Energy and modified gravity

w(z)

Observational signatures of Jordan–Brans–Dicke theories of gravity

). Using observations of passively evolving galaxies and supernova data we derive constraints on the dark energy potential shape in the redshift range

Considerations in optimizing CMB polarization experiments to constrain inflationary physics

0.1lzl1.8

Baryonic conversion tree: the global assembly of stars and dark matter in galaxies from the Sloan Digital Sky Survey

. Our findings show that at the

Correlation properties of the kinematic Sunyaev-Zel'dovich effect and implications for dark energy

1ensuremath{sigma}

Smoothing spline primordial power spectrum reconstruction

level the potential is consistent with being constant, although at the same level of confidence variations cannot be excluded with current data. We forecast constraints achievable with future data from the Atacama Cosmology Telescope.

Limits on deviations from the inverse-square law on megaparsec scales

ABSTRACT The Fisher matrix approach (Fisher (1935)) allows one to calculate in advance howwell a given experiment will be able to estimate model parameters, and has been aninvaluable tool in experimental design. In the same spirit, we present here a methodto predict how well a given experiment can distinguish between different models, re-gardless of their parameters. From a Bayesian viewpoint, this involves computation ofthe Bayesian evidence. In this paper, we generalise the Fisher matrix approach fromthe context of parameter fitting to that of model testing, and show how the expectedevidence can be computed under the same simplifying assumption of a gaussian like-lihood as the Fisher matrix approach for parameter estimation. With this ‘Laplaceapproximation’ all that is needed to compute the expected evidence is the Fisher ma-trix itself. We illustrate the method with a study of how well upcoming and plannedexperiments should perform at distinguishing between Dark Energy models and mod-ified gravity theories. In particular we consider the combination of 3D weak lensing,for which planned and proposed wide-field multi-band imaging surveys will providesuitable data, and probes of the expansion history of the Universe, such as proposedsupernova and baryonic acoustic oscillations surveys. We find that proposed large-scale weak lensing surveys from space should be able readily to distinguish GeneralRelativity from modified gravity models.Key words: methods: statistical, cosmological parameters, dark energy

The Thermal Sunyaev-Zel’dovich Signature of Baryons in the Local Universe

We analyze the Jordan–Brans–Dicke model (JBD) of gravity, where deviations from general relativity (GR) are described by a scalar field non-minimally coupled to the graviton. The theory is characterized by a constant coupling parameter, ωJBD; GR is recovered in the limit . In such theories, gravity modifications manifest at early times, so one cannot rely on the usual approach of looking for inconsistencies in the expansion history and perturbation growth in order to discriminate between JBD and GR. However, we show that a similar technique can be successfully applied to early and late time observables instead. Cosmological parameters inferred extrapolating early time observations to the present will match those recovered from direct late time observations only if the correct gravity theory is used. We use the primary cosmic microwave background, as will be seen by the Planck satellite, as the early time observable; and forthcoming and planned supernovae, baryonic acoustic oscillations and weak lensing experiments as late time observables. We find that detection of values of ωJBD as large as 500 and 1000 is within reach of the upcoming (2010) and next-generation (2020) experiments, respectively.

Fast cosmological parameter estimation from microwave background temperature and polarization power spectra

We quantify the limiting factors in optimizing current-technology cosmic microwave background (CMB) polarization experiments to learn about inflationary physics. We consider space-based, balloon-borne and ground-based experiments. We find that foreground contamination and residuals from foreground subtraction are ultimately the limiting factors in detecting a primordial gravity wave signal. For full-sky space-based experiments, these factors hinder the detection of tensor-to-scalar ratios of rxa0 xa03xa0σ) tensor component in a realistic CMB experiment, inflation must either involve large field variations, or multi-field/hybrid models. Hybrid models can be easily distinguished from large field models due to their blue scalar spectral index. Therefore, an observation of a tensor/scalar ratio and nxa0<xa01 in future experiments with the characteristics considered here may be an indication that inflation is being driven by some physics in which the inflaton cannot be described as a fundamental field.