Decrumpling or TVSD model explains why the universe is accelerating   today
  Within the framework of a model universe with time variable space dimension (TVSD), known as decrumpling or TVSD model, we show the present value of the deceleration parameter is negative implying that the universe is accelerating today. Our study is based on a flat universe with the equation of state parameter to be $\omega(z=0) \approx -1$ today. More clearly, decrumpling model tells us the universe is accelerating today due to the cosmological constant which is the simplest candidate for the dark energy. 
Forough Nasseri