Lorentz invariant dark-spinor and inflation

Abstract

We investigate the possibility of the inflation driven by a Lorentz invariant\nnon-standard spinor field. As these spinors are having dominant interaction via\ngravitational field only, they are considered as \\emph{Dark Spinors}. We study\nhow these dark-spinors can drive the inflation and investigate the cosmological\n(scalar) perturbations generated by them. Though the dark-spinors obey a\nKlein-Gordon like equation, the underlying theory of the cosmological\nperturbations is far more complex than the theories which are using a canonical\nscalar field. For example the sound speed of the perturbations is not a\nconstant but varies with time. We find that in order to explain the observed\nvalue of the spectral-index $n_s$ one must have upper bound on the values of\nthe background NSS-field. The tensor to scalar ratio remains as small as that\nin the case of canonical scalar field driven inflation because the correction\nto tensor spectrum due to NSS is required to be very small. In addition we\ndiscuss the relationship of results with previous results obtained by using the\nLorentz invariance violating theories.\n