Thermodynamics of Apparent Horizon and Friedmann Equations in Big Bounce   Universe
  In this paper, we study a big bounce universe typified by a non-singular big bounce, as opposed to a singular big bang. This cosmological model can describe radiation dominated early universe and matter dominated late universe in FRW model. The connections between thermodynamics and gravity are observed here. In the early stage of both cold and hot universes, we find there is only one geometry containing a 4D de Sitter universe with a general state parameter. We also find the form of the apparent horizon in the early universe strongly depends on the extra dimension, which suggests that the influence of the extra dimension could in principle be found in the early universe. Moreover, we show that in the late stages of both cold and hot universes, the moment when the apparent horizon begins to bounce keeps essentially in step with the behavior of the cosmological scalar factor. 
Molin Liu, Yuling Yang, Jianbo Lv and Lixin Xu
gr-qc