19 research outputs found

    Wormholes in R2R^2-gravity within the f(R,T)f(R,T) formalism

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    We propose, as a novelty in the literature, the modelling of wormholes within the particular case of the f(R,T)f(R,T) gravity, namely f(R,T)=R+αR2+λTf(R,T)=R+\alpha R^{2}+\lambda T, with RR and TT being the Ricci scalar and trace of the energy-momentum tensor, respectively, while α\alpha and λ\lambda are constants. Although such a functional form application can be found in the literature, those concern to compact astrophysical objects, such that no wormhole analysis has been done so far. The quadratic geometric and linear material corrections of this theory make the matter content of the wormhole to remarkably be able to obey the energy conditions.Comment: Published versio

    f(R,T)=f(R)+λTf(R,T)=f(R)+\lambda T gravity models as alternatives to cosmic acceleration

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    This article presents cosmological models that arise in a subclass of f(R,T)=f(R)+f(T)f(R,T)=f(R)+f(T) gravity models, with different f(R)f(R) functions and fixed TT-dependence. That is, the gravitational lagrangian is considered as f(R,T)=f(R)+λTf(R,T)=f(R)+\lambda T, with constant λ\lambda. Here RR and TT represent the Ricci scalar and trace of the stress-energy tensor, respectively. The modified gravitational field equations are obtained through the metric formalism for the Friedmann-Lema\^itre-Robertson-Walker metric with signature (+,,,)(+,-,-,-). We work with f(R)=R+αR2μ4Rf(R)=R+\alpha R^2-\frac{\mu^4}{R}, f(R)=R+kln(γR)f(R)=R+k\ln(\gamma R) and f(R)=R+me[nR]f(R)=R+me^{[-nR]}, with α,μ,k,γ,m\alpha, \mu, k, \gamma, m and nn all free parameters, which lead to three different cosmological models for our Universe. For the choice of λ=0\lambda=0, this reduces to widely discussed f(R)f(R) gravity models. This manuscript clearly describes the effects of adding the trace of the energy-momentum tensor in the f(R)f(R) lagrangian. The exact solution of the modified field equations are obtained under the hybrid expansion law. Also we present the Om diagnostic analysis for the discussed models.Comment: 11 pages, 20 figures, Accepted version in EPJ

    Mixed fluid cosmological model in f(R,T)f(R,T) gravity

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    We construct Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model in f(R,T)f(R,T) theory of gravity when the source of gravitation is the mixture of barotropic fluid and dark energy (DE) by employing a time varying deceleration parameter (DP). We observe through the behavior of the state finder parameters (r,s)(r, s) that our model begins from the Einstein static era and goes to Λ\LambdaCDM era. The EoS parameter(ωd\omega_d) for DE varies from phantom (ω1\omega-1) phase which is consistent with the observational results. It is found that the discussed model can reproduce the current accelerating phase of expansion of the universe.Comment: 9 pages, 7 figures, accepted version for publication in Canadian Journal of Physic
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