Cosmic holography

A version of the holographic principle for cosmology is proposed which dictates that the particle entropy within the cosmological apparent horizon should not exceed the gravitational entropy associated with the apparent horizon. It is shown that in Friedmann-Robertson-Walker (FRW) cosmology, the open universe, as well as a restricted class of Rat cases, are compatible with the principle, whereas the closed universe is not. it is also found that the inflationary universe after the big bang is incompatible with cosmic holography.