Semi-Holographic Universe
  By assuming that a dark component (dark energy) in the universe strictly
obeys the holographic principle, that is, its entropy is one fourth of the
apparent horizon, we find that the existence of the other dark component (dark
matter) is compulsory, as a compensation of dark energy, based on the first law
of thermodynamics. By using the method of dynamical system analysis, we find
that there exists a stable dark energy-dark matter scaling solution at late
time, which is helpful to solve the coincidence problem. For reasonable
parameters, the deceleration parameter is well consistent with current
observations.
