  The discovery of accelerated cosmic expansion implies that, in addition to
the attractive gravity of matter, there exists in our universe some other form
of energy (dark energy or cosmological constant) producing a repulsive force.
The natural interpretation of dark energy is the vacuum energy. However, the
density of vacuum energy expected by the quantum field theory is 120 orders of
magnitude larger than what is allowed by cosmological observations, which is
called the cosmological constant problem and remains one of the most
significant unsolved problems in fundamental physics. Here we show that the
huge discrepancy can be resolved by assuming that our universe is an
attraction-repulsion coupled system with energy conservation, and that the
pre-inflation vacuum is in equilibrium between attraction and repulsion (in
flat Minkowski spacetime, not de Sitter or anti de Sitter). The
attraction-repulsion coupling picture can also easily explain why both kinds of
energy in our universe have similar magnitude today, and avoid singularity
problems in general relativity and cosmology.
