F(T) cosmology: from Pseudo-Bang to Pseudo-Rip

Abstract

We investigate the complete universe evolution in the framework off(T) cosmology. We first study the requirements at thekinematic level and we introduce a simple scale factor with the necessaryfeatures. Performing a detailed analysis of the phaseportrait we show that the universe begins in the infinite past from aphase where thescale factor goes to zero but the Hubble parameter goes to a constant, and itsderivative to zero. Since these features resemble those of the Pseudo-Ripfate but in a revered way, we call this initial phaseas Pseudo-Bang. Then the universe evolves in a first inflationary phase, acosmological turnaround and a bounce, after which we have asecond inflationary regime with a successful exit. Subsequently we obtainthe standard thermal history and the sequence of radiation, matter andlate-time acceleration epochs, showing that the universe will result inan everlasting Pseudo-Rip phase. Finally, taking advantage of the fact thatthe field equations of f(T) gravity are of second order, and therefore thecorresponding autonomous dynamical system is one dimensional, we incorporate the aforementioned kinematicfeatures and we reconstruct the specific f(T)form that can dynamically generate the Pseudo-Bang cosmological scenario. Lastly, we examine the evolution of the primordial fluctuationsshowing that they are initially sub-horizon, and we show thatthe total fluid does not exhibit any singular behaviour at thephantom crossing points, while the torsional fluid experiencesthem as Type II singular phases.