Extra-Acceleration at Large Scale due to Merging at Small Scales

Merging of cosmic objects at small scales is regarded as a possible source for explaining the extra-acceleration of the universe at large scale. Inspired by chemical association, merging of cosmic objects introduces a correction term in the perfect fluid equation of state in the form of $P=w\rho+b\rho^2$. Alternative relations for the energy density and scale factor evolution in the FRLW framework are obtained that coincide with the conventional results in the perfect fluid limit. Invoking the observational constraint for the equation of state parameter $w$ and the deceleration parameter, we show that the simultaneous merging of cosmic objects such as galaxies on one hand and voids on the other, will act as a source of extra-accelerating in the universe at large scale.