Browsing by Author "Tossa, J."

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    Cosmological Study of Autonomous Dynamical Systems
    (Research Gate, 2018-04-25) Ganiou, M.G; Logbo, P.H; Houndjo, M.J.S; Tossa, J.
    Cosmological approaches of autonomous dynamical system in the framework of f(T ) gravity are investigated in this paper. Our methods applied to flat Friedmann-Robertson Walker equations in f(T ) gravity, consist to extract dynamical systems whose time-dependence is contained in a single parameter m depending on the Hubble rate of Universe and its second derivative. In our attempt to investigate the autonomous aspect of the dynamical systems reconstructed in both vacuum and non-vacuum f(T ) gravities, two values of the parameter m have been considered for our present analysis. In the so-called quasi-de Sitter inflationary era (m ≃ 0), the corresponding autonomous dynamical systems provide stable de Sitter attractors and unstable de Sitter fixed points. Especially in the vacuum f(T ) gravity, the approximate form of the f(T ) gravity near the stable and the unstable de Sitter fixed points has been performed. The matter dominated era case (m = −9/2) leads to unstable fixed points confirming matter dominated era or not, and stable attractor fixed point describing dark energy dominated era. Another subtlety around the stable fixed point obtained at matter dominated case in the non-vacuum f(T ) gravity is when the dark energy dominated era is reached, at the same time, the radiation perfect fluid dominated succumbs.
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    New Traversable Wormholes Solutions in f(T) Gravity
    (arXiv, 2018-09-08) Tefo, R.C.; Logbo, P.H.; Houndjo, M.J.S.; Tossa, J.
    In this paper we search for dynamical traversable wormhole solution in the modified f(T ) theory of gravity, T being the torsion scalar. For such wormhole, the time dependence is inserted in the static traversable wormhole metric of Morris and Thore. Two set of tetrads are adopted: the diagonal and the non-diagonal tetrads. The diagonal set of tetrads constrains and reduces f(T ) model to teleparallel theory where usual solutions have been found. With diagonal set of tetrads, free from the teleparallel theory constraint, our results show that the existence of traversable wormhole is possible only for non-dynamical spacetime metric, i.e, static traversable wormhole solutions. Moreover we take into account energy condition analysis and the results show that the violation of NEC is not determinant for existence of static traversable wormhole solutions.