Solving the main cosmological puzzles with a generalized time varying vacuum energy
Research Center for Astronomy, Academy of Athens, 11527 Athens, Greece e-mail: svasil@academyofathens.gr
Received:
26
May
2009
Accepted:
12
October
2009
We study the dynamics of the FLRW flat cosmological models
in which the vacuum energy density varies with time, 
.
In particular, we investigate the dynamical
properties of a generalized vacuum model, and we
find that under certain circumstances the vacuum term in the
radiation era varies as 
,
while in the matter era
we have 
up to
and 
for 
.
The confirmation of such a behavior would be of paramount importance
because it could provide a solution
to the cosmic coincidence problem as well as to the fine-tuning
problem, without changing the
well known (from the concordance Λ-cosmology) Hubble expansion.
Key words: cosmology: theory / methods: analytical
© ESO, 2009