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.
