An interpretation of the acceleration of the universe's expansion
  We have observed the acceleration of the expansion of the universe. To
explain this phenomenon, we usually introduce the dark energy (DE) which has a
negative pressure or we need to modify the Einstein's equation to produce a
term which is equivalent to the dark energy. Are there other possibilities?
Combining our previous works of statistical mechanics of self-gravitating
system with the derivation of van der waals equation, we propose a different
matter's equation of state (EoS) in this paper. Then we find that if the
matter's density is low enough, its pressure can be negative, which means that
it is the matter that drives the expansion's acceleration. So here we will not
need to add the DE to the universe. Our results also predict that the universe
finally tends to be dominated by an approximate constant energy density, but
its value can be smaller than DE. The data of Supernova can not differentiate
our model from the standard model, but they may indicate some deviations from
LCDM.
