B1 - Early Dark Energy
Early Dark Energy might constitute an observable fraction of the total
energy density of our Universe as far back as the time of matter
radiation equality or even big bang nucleosynthesis. This is in sharp
contrast to a cosmological constant or dark energy with a constant
negative equation of state -- for those the fraction in dark energy,
, is negligible at high redshift.
Hence, a detection of Early Dark Energy
would favor some form of
dynamical dark energy over a cosmological constant.
Models predicting Early Dark Energy usually link the small present
dark energy density to the huge age of our Universe.
In such models the dark energy fraction
is only mildly varying with
redshift at early times. One might thus hope to find a
few percent of dark energy during structure formation and at
recombination. A detection seems feasible,
because Early Dark Energy alters the spectrum of CMB
anisotropies and the growth of linear and nonlinear structures.
There are two major objectives of this project.
One is to collect all available information
contained in observations that are sensitive to the presence of early
dark energy. We plan to limit or extract the behavior of
in particular for redshifts
. A main tool for this will be the Cmbeasy
at Heidelberg and at Dartmouth college.
The other main objective is to develop
viable phenomenological quintessence models that can be used as an
input for the tests of
in the observational projects
concerning the time variation of Dark Energy. The whole project is conceived in close
interaction with all projects in part B.