A solution of the dark energy and its coincidence problem based on local
  antigravity sources without fine-tuning or new scales
  A novel idea is proposed for a natural solution of the dark energy and its
cosmic coincidence problem. The existence of local antigravity sources,
associated with astrophysical matter configurations distributed throughout the
universe, can lead to a recent cosmic acceleration effect. Various physical
theories can be compatible with this idea, but here, in order to test our
proposal, we focus on quantum originated spherically symmetric metrics matched
with the cosmological evolution through the simplest Swiss cheese model. In the
context of asymptotically safe gravity, we have explained the observed amount
of dark energy using Newton's constant, the galaxy or cluster length scales,
and dimensionless order one parameters predicted by the theory, without
fine-tuning or extra unproven energy scales. The interior modified
Schwarzschild-de Sitter metric allows us to approximately interpret this result
as that the standard cosmological constant is a composite quantity made of the
above parameters, instead of a fundamental one.
