Bianchi Type I Cosmology with Scalar and Spinor Tachyon

Recently, some authors propose a scenario where inflation is driven by scalar and spinor fields. In this scenario, the universe undergoes anisotropic inflationary expansion due to a preferred direction dominated by spinor. The main question arises that what is the origin of spinor inflation in 4D Universe? To answer to this question , we propose a new model in super string theory that allows to take into account the spinor string tachyon in additional to scalar one which stretch between branes and antibranes. In this model, the inflation of 4D Universe is controlled by the spinor type of tachyon and evolves from non-phantom phase to phantom one and consequently, phantom-dominated era of the universe accelerates and ends up in big-rip singularity. We test our model against WMAP and Planck data and obtain the ripping time. We find that the finite time that Big Rip singularity occurs is t = 65(Gyr). According to our calculations, N ≃ 60 case leads to ns ≃ 0.96, where N and ns are the number e-folds and the spectral index respectively. Thus our results are consistent with experimental data and thus the spinor inflationary model works.