3,651 research outputs found
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.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Letter
Frontiers of Dark Energy
Cosmologists are just beginning to probe the properties of the cosmic vacuum
and its role in reversing the attractive pull of gravity to cause an
acceleration in the expansion of the cosmos. The cause of this acceleration is
given the generic name of dark energy, whether it is due to a true vacuum, a
false, temporary vacuum, or a new relation between the vacuum and the force of
gravity. Despite the common name, the distinction between these origins is of
utmost interest and physicists are actively engaged in finding ways to use
cosmological observations to distinguish which is the true, new physics. Here
we will discuss how to relate the theoretical ideas to the experimental
constraints, how to understand the influences of dark energy on the expansion
and structure in the universe, and what frontiers of new physics are being
illuminated by current and near-term data.Comment: 25 pages, 7 figures; invited review chapter for book aimed at general
scientists; v2 fixed sign typos in Eqs. 1.2-1.
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