Institute Of Mathematiques Et Of Science Physiques Imsp

Porto-Novo, Benin

Institute Of Mathematiques Et Of Science Physiques Imsp

Porto-Novo, Benin
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Houndjo M.J.S.,Federal University of Espirito Santo | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | Batista C.E.M.,State University of Feira de Santana | Campos J.P.,Federal University of Recôncavo da Bahia | Piattella O.F.,Federal University of Espirito Santo
Canadian Journal of Physics | Year: 2013

We investigate f(R, T) gravity models (where R is the curvature scalar and T is the trace of the stress-energy tensor of ordinary matter) that are able to reproduce the four known types of future finite-time singularities. We choose a suitable expression for the Hubble parameter to realise the cosmic acceleration and we introduce two parameters, α and Hs, which characterise each type of singularity. We address the conformal anomaly and we observe that it cannot remove the sudden singularity or the Big Brake, but, for some values of α, the Big Rip and the Big Freeze may be avoided. We also find that, even without taking into account the conformal anomaly, the Big Rip and the Big Freeze may be removed thanks to the presence of the T contribution of the f(R, T) theory. © 2013 Published by NRC Research Press.


Alvarenga F.G.,CEUNES | De La Cruz-Dombriz A.,University of Cape Town | Houndjo M.J.S.,CEUNES | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | And 3 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In the context of f(R,T) theories of gravity, we study the evolution of scalar cosmological perturbations in the metric formalism. According to restrictions on the background evolution, a specific model within these theories is assumed in order to guarantee the standard continuity equation. Using a completely general procedure, we find the complete set of differential equations for the matter density perturbations. In the case of sub-Hubble modes, the density contrast evolution reduces to a second-order equation. We show that for well-motivated f(R,T) Lagrangians the quasistatic approximation yields to very different results from the ones derived in the frame of the concordance ΛCDM model constraining severely the viability of such theories. © 2013 American Physical Society.


Houndjo M.J.S.,Federal University of Bahia | Monwanou A.V.,Institute Of Mathematiques Et Of Science Physiques Imsp | Chabi Orou J.B.,Institute Of Mathematiques Et Of Science Physiques Imsp
International Journal of Modern Physics D | Year: 2011

We investigate particle production in an expanding universe under the assumption that the Lagrangian contains the Einstein term R plus a modified gravity term of the form R α, where α is a constant. Dark fluid is considered as the main content of the universe and the big rip singularity appears. Quantum effects due to particle creation is analyzed near the singularity and we find that for α ∈ ]1/2, 1[, quantum effects are dominant and the big rip may be avoided whereas for α ∈ J the dark fluid is dominant and the singularity remains. The Cardy-Verlinde formula is also introduced and its equivalence with the total entropy of the universe is checked. It is found that this can always occur in Einstein gravity while in f(R) gravity, it holds only for α = n+1/2n+6, n being the space dimension, corresponding to the situation in which the big rip cannot be avoided. © 2011 World Scientific Publishing Company.


Houndjo M.J.S.,Federal University of Espirito Santo | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | Rodrigues M.E.,Federal University of Espirito Santo | Momeni D.,Eurasian University | Myrzakulov R.,Eurasian University
Canadian Journal of Physics | Year: 2014

We present detailed cylindrically symmetric solutions for a type of Gauss-Bonnet gravity. We derive the full system of field equations and show that there exist seven families of exact solutions for three forms of viable models. By applying the method based on the effective fluid energy momentum tensor components, we evaluate the mass per unit length for the solutions. From a dynamical point of the view, by evaluating the null energy condition for these configurations, we show that in some cases the azimuthal pressure breaks the energy condition. This violation of the null energy condition predicts the existence of a cylindrical wormhole. © 2014 Published by NRC Research Press.


Setare M.R.,Payame Noor University | Houndjo M.J.S.,Federal University of Espirito Santo | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp
Canadian Journal of Physics | Year: 2013

We investigate models of future finite-time singularities in f(T) theory, where T is the torsion scalar. The algebraic function f(T) is the teleparallel term, T, plus an arbitrary function, g(T). A suitable expression for the Hubble parameter is assumed and constraints are imposed to provide an expanding universe. Two parameters, β and Hs, that appear in the Hubble parameter are relevant in specifying the types of singularities. Differential equations of g(T) are established and solved, leading to algebraic f(T) models for each type of future finite-time singularity. Moreover, we take into account the viscosity in the fluid and discuss three interesting cases: constant viscosity, viscosity proportional to-T, and the general one where the viscosity is proportional to (-T)n/2, where n is a natural number. We see that for the first and second cases, in general, the singularities are robust against the viscous fluid, while for the general case, the Big Rip and the Big Freeze can be avoided from the effects of the viscosity for some values of n. © 2013 Published by NRC Research Press.


Setare M.R.,University of Kurdistan | Houndjo M.J.S.,Federal University of Espirito Santo | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp
Canadian Journal of Physics | Year: 2013

We study particle production in a flat Friedmann-Robertson-Walker universe in the framework of f(T) gravity. An exact power-law solution is obtained by solving the Friedmann equations and assuming that matter is minimally coupled with gravitation. The torsion scalar, T, appears to plays the same role as the curvature (Ricci scalar) in general relativity (GR) and its modified theories, f(R). Particularly, in the phantom phase, we observe that the vacuum state corresponds to a vanishing torsion scalar and particle production becomes important as the torsion scalar diverges. This aspect not only provides the equivalence between teleparallel gravity and GR, but also between their respective modified versions, f(T) and f(R), in the view of massless particle production phenomenon when matter is minimally coupled with gravity. However, when the gravitational and scalar fields are not minimally coupled, it appears that this similarity between the teleparallel gravity and GR may break down, because the torsion scalar no longer has the same time-dependent expression as the Ricci scalar. © 2013 Published by NRC Research Press.


Hamani Daouda M.,Federal University of Espirito Santo | Hamani Daouda M.,University Abdou Moumouni | Rodrigues M.E.,Federal University of Espirito Santo | Houndjo M.J.S.,Federal University of Espirito Santo | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We consider f(T) gravity for a Weitzenbock's spherically symmetric and static spacetime, where the metric is projected in the tangent space to the manifold, for a set of non-diagonal tetrads. The matter content is coupled through the energy-momentum tensor of an anisotropic fluid, generating various classes of new black hole and wormhole solutions. One of these classes is that of cold black holes. We also perform the reconstruction scheme of the algebraic function f(T) for two cases where the radial pressure is proportional to f(T) and its first derivative. © 2012 Elsevier B.V.


Junior E.L.B.,Federal University of Pará | Rodrigues M.E.,Federal University of Pará | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | Houndjo M.J.S.,University of Parakou
Journal of Cosmology and Astroparticle Physics | Year: 2015

We seek to obtain a new class of exact solutions of regular black holes in f(T) Gravity with non-linear electrodynamics material content, with spherical symmetry in 4D. The equations of motion provide the regaining of various solutions of General Relativity, as a particular case where the function f(T)=T. We developed a powerful method for finding exact solutions, where we get the first new class of regular black holes solutions in the f(T) Theory, where all the geometrics scalars disappear at the origin of the radial coordinate and are finite everywhere, as well as a new class of singular black holes. © 2015 IOP Publishing Ltd and Sissa Medialab srl .


Junior E.L.B.,Federal University of Pará | Rodrigues M.E.,Federal University of Pará | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | Houndjo M.J.S.,University of Parakou
Journal of Cosmology and Astroparticle Physics | Year: 2015

We investigate f(T) theory coupled with a nonlinear source of electrodynamics, for a spherically symmetric and static spacetime in 4D. We re-obtain the Born-Infeld and Reissner-Nordstrom-AdS solutions. We generalize the no-go theorem for any content that obeys the relationship 00=11 for the energy-momentum tensor and a given set of tetrads. Our results show new classes of solutions where the metrics are related through b(r)=-Na(r). We do the introductory analysis showing that solutions are that of asymptotically flat black holes, with a singularity at the origin of the radial coordinate, covered by a single event horizon. We also reconstruct the action for this class of solutions and obtain the functional form f(T)=f0(-T)(N+3)/[2(N+1)] and NED=0(-F)(N+3)/[2(N+1)]. Using the Lagrangian density of Born-Infeld, we obtain a new class of charged black holes where the action reads f(T)=-16βBI[1-1+(T/4βBI)]. © 2015 IOP Publishing Ltd and Sissa Medialab srl.


Rodrigues M.E.,Federal University of Pará | Salako I.G.,Institute Of Mathematiques Et Of Science Physiques Imsp | Houndjo M.J.S.,Institute Of Mathematiques Et Of Science Physiques Imsp | Houndjo M.J.S.,University of Parakou | Tossa J.,Institute Of Mathematiques Et Of Science Physiques Imsp
International Journal of Modern Physics D | Year: 2014

We study the locally rotational symmetry Bianchi type-I dark energy model in the framework of f(T) theory of gravity, where T denotes the torsion scalar. A viable cosmological model is undertaken and the isotropization of this latter is checked, yielding a result that reflects the real evolution of our universe. Moreover, still in the anisotropic optic, a more complicated f(T) model is obtained from the cosmological reconstruction scheme and the analysis shows that the universe is more anisotropic at the beginning if the terms of higher order in T are not considered. This means that the nonlinear model should be favored by observational data. © World Scientific Publishing Company.

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