The Interacting and Non-constant Cosmological Constant
  We propose a time-varying cosmological constant with a fixed equation of
state, which evolves mainly through its interaction with the background during
most of the long history of the universe. However, such interaction does not
exist in the very early and the late-time universe and produces the
acceleration during these eras when it becomes very nearly a constant. It is
found that after the initial inflationary phase, the cosmological constant,
that we call as lambda parameter, rolls down from a large constant value to
another but very small constant value and further dominates the present epoch
showing up in form of the dark energy driving the acceleration.
