Cosmic holography

A version of the holographic principle for cosmology is proposed which dict ates that the particle entropy within the cosmological apparent horizon sho uld not exceed the gravitational entropy associated with the apparent horiz on. It is shown that in Friedmann-Robertson-Walker (FRW) cosmology, the ope n 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 t he inflationary universe after the big bang is incompatible with cosmic hol ography.