Eric V. Linder

Exploring the expansion history of the universe

Exploring the recent expansion history of the universe promises insights into the cosmological model, the nature of dark energy, and potentially clues to high energy physics theories and gravitation. We examine the extent to which precision distance-redshift observations can map out the history, including the acceleration-deceleration transition, and the components and equations of state of the energy density. We consider the ability to distinguish between various dynamical scalar field models for the dark energy, as well as higher dimension and alternate gravity theories. Finally, we present a new, advantageous parametrization for the study of dark energy.

Cosmic growth history and expansion history

Author(s): Linder, Eric V. | Abstract: The cosmic expansion history tests the dynamics of the global evolution of the universe and its energy density contents, while the cosmic growth history tests the evolution of the inhomogeneous part of the energy density. Precision comparison of the two histories can distinguish the nature of the physics responsible for the accelerating cosmic expansion: an additional smooth component - dark energy - or a modification of the gravitational field equations. With the aid of a new fitting formula for linear perturbation growth accurate to 0.05-0.2percent, we separate out the growth dependence on the expansion history and introduce a new growth index parameter \gamma that quantifies the gravitational modification.

Effects of systematic uncertainties on the supernova determination of cosmological parameters

Mapping the recent expansion history of the universe offers the best hope for uncovering the characteristics of the dark energy believed to be responsible for the acceleration of the expansion. In determining cosmological and dark-energy parameters to the percent level, systematic uncertainties impose a floor on the accuracy more severe than the statistical measurement precision. We delineate the categorization, simulation, and understanding required to bound systematics for the specific case of the Type Ia supernova method. Using simulated data of forthcoming ground-based surveys and the proposed space-based SNAP mission we present Monte Carlo results for the residual uncertainties on the cosmological parameter determination. The tight systematics control with optical and near-infrared observations and the extended redshift reach allow a space survey to bound the systematics below 0.02 magnitudes at z = 1.7. For a typical SNAP-like supernova survey, this keeps total errors within 15% of the ′ ′ � ,

Baryon oscillations as a cosmological probe

Mapping the expansion of the Universe gives clues to the underlying physics causing the recently discovered acceleration of the expansion, and enables discrimination among cosmological models. We examine the utility of measuring the rate of expansion,

Redshift distortions as a probe of gravity

H(z),

Testing the cosmological constant as a candidate for dark energy

at various epochs, both alone and in combination with distance measurements. Because of parameter degeneracies, it proves most useful as a complement to precision distance-redshift data. Using the baryon oscillations in the matter power spectrum as a standard rod allows determination of

STRONG LENS TIME DELAY CHALLENGE. II. RESULTS OF TDC1

H(z)/({\ensuremath{\Omega}}_{m}{h}^{2}{)}^{1/2}

Growth of cosmic structure: Probing dark energy beyond expansion

free of most major systematics, and thus provides a window on dark energy properties. We discuss the addition of this data from a next generation galaxy redshift survey such as KAOS to precision distance information from a next generation supernova survey such as SNAP. This can provide useful crosschecks as well as lead to improvement on estimation of a time variation in the dark energy equation of state by factors ranging from 15\char21{}50 %.

Importance of supernovae at z > 1.5 to probe dark energy

Abstract Redshift distortion measurements from galaxy surveys include sensitivity to the gravitational growth index distinguishing other theories from Einstein gravity. This gravitational sensitivity is substantially free from uncertainty in the effective equation of state of the cosmic expansion history. We estimate the future sensitivity and complementarity of this technique exploring the growth history of the universe. We also illustrate the bias in the traditional application to matter density determination using f = Ω m ( a ) 0.6 , and how to avoid it.

Probing dark energy with supernovae: Exploiting complementarity with the cosmic microwave background

It may be difficult to single out the best model of dark energy on the basis of the existing and planned cosmological observations, because many different models can lead to similar observational consequences. However, each particular model can be studied and either found consistent with observations or ruled out. In this paper, we concentrate on the possibility to test and rule out the simplest and by far the most popular of the models of dark energy, the theory described by general relativity with positive vacuum energy (the cosmological constant). We evaluate the conditions under which this model could be ruled out by the future observations made by the Supernova/Acceleration Probe SNAP (both for supernovae and weak lensing) and by the Planck Surveyor cosmic microwave background satellite.