Role of higher -dimensional evolving wormholes in the formation of a big   rip singularity
  We study the evolutions of 4D universe on the M2-M5 BIon in the thermal background. The BIon consists of a D-brane and a parallel anti-D-brane which a wormhole connects them. When the branes and antibranes are far from each other and the brane's spike and the antibrane's spike are well separated, the wormhole cannot be built. However, when the branes and anti-branes are close to each other, a wormhole can be formed between them. Under this condition, there are many ways for flowing energy from transverse dimensions into our universe. This energy overcomes all other forms of energy, such as the gravitational repulsion and causes that our epoch is terminated at a Big-Rip singularity. We show that at this point, universe would be disappeared and one black M2-brane is formed. Finally, we examine our model against WMAP, Planck and BICEP2 experiments and get the ripping time. Comparing the model with experimental data, we obtain $N\simeq 50$ and $n_{s}\simeq 0.96$, where \emph{N} and $n_{s}$ are the number e-folds and the spectral index respectively. These results could be located in $0.01 < R_{Tensor-scalar} < 0.3$, where $R_{Tensor-scalar}$ is the tensor-scalar ratio. In this epoch, the Big Rip singularity happens in a finite time $t_{rip}=31(Gyr)$ for WMAP and Planck experimnts and $t_{rip}=28(Gyr)$ for BICEP2 experiment. By comparing this time with the time of the Big Rip in brane-antibrane, we observe that the wormhole in BIonic system causes that the destruction of the universe becomes faster. 
Mohammad Reza Setare, Alireza Sepehri
gr-qc hep-th