73 research outputs found

    Generalised nonminimally gravity-matter coupled theory

    Get PDF
    In this paper, a new generalised gravity-matter coupled theory of gravity is presented. This theory is constructed by assuming an action with an arbitrary function f(T,B,Lm)f(T,B,L_m) which depends on the scalar torsion TT, the boundary term B=μTμB=\nabla_{\mu}T^{\mu} and the matter Lagrangian LmL_m. Since the function depends on BB which appears in R=T+BR=-T+B, it is possible to also reproduce curvature-matter coupled models such as f(R,Lm)f(R,L_m) gravity. Additionally, the full theory also contains some interesting new teleparallel gravity-matter coupled theories of gravities such as f(T,Lm)f(T,L_m) or C1T+f(B,Lm)C_1 T+ f(B,L_m). The complete dynamical system for flat FLRW cosmology is presented and for some specific cases of the function, the corresponding cosmological model is studied. When it is necessary, the connection of our theory and the dynamical system of other well-known theories is discussed.Comment: Matches published version in EPJ

    Is Gravity Actually the Curvature of Spacetime?

    Get PDF
    The Einstein equations, apart from being the classical field equations of General Relativity, are also the classical field equations of two other theories of gravity. As the experimental tests of General Relativity are done using the Einstein equations, we do not really know, if gravity is the curvature of a torsionless spacetime, or torsion of a curvatureless spacetime, or if it occurs due to the non-metricity of a curvatureless and torsionless spacetime. However, as the classical actions of all these theories differ from each other by boundary terms, and the Casimir effect is a boundary effect, we propose that a novel gravitational Casimir effect between superconductors can be used to test which of these theories actually describe gravity.Comment: Essay received an honorable mention in the Gravity Research Foundation Essay Competition 2019. 7 page

    Noether Symmetry Approach in f(T,B)f(T,B) teleparallel cosmology

    Full text link
    We consider the cosmology derived from f(T,B)f(T,B) gravity where TT is the torsion scalar and B=2eμ(eTμ)B=\frac{2}{e}\partial_{\mu}(e T^{\mu}) a boundary term. In particular we discuss how it is possible to recover, under the same standard, the teleparallel f(T)f(T) gravity, the curvature f(R)f(R) gravity and the teleparallel-curvature f(R,T)f(R,T) gravity, which are particular cases of f(T,B)f(T,B). We adopt the Noether Symmetry Approach to study the related dynamical systems and to find out cosmological solutions.Comment: 21 page

    Stability of a dd-dimensional thin-shell wormhole surrounded by quintessence

    Get PDF
    We study the stability of different higher dimensional thin--shell wormholes (HDTSW) in general relativity with a cosmological constant. We show that a dd--dimensional thin--shell wormhole surrounded by quintessence can have three different throat geometries: spherical, planar and hyperbolic. Unlike the spherical geometry, the planar and hyperbolic geometries allow different topologies that can be interpreted as higher-dimensional domain walls or branes connecting two universes. To construct these geometries, we use the cut-and-paste procedure by joining two identical vacuum spacetime solutions. Properties such as the null energy condition and geodesics are also studied. A linear stability analysis around the static solutions is carried out. Our stability analysis takes into account a more general HDTSW geometry than previous works so it is possible to recover other well-known stability HDTSW conditions.Comment: 10 pages; 3 figures; matches the accepted version, to appear in Gravitation and Cosmolog

    (N+1)-dimensional Lorentzian evolving wormholes supported by polytropic matter

    Full text link
    In this paper we study (N+1)(N+1)-dimensional evolving wormholes supported by energy satisfying a polytropic equation of state. The considered evolving wormhole models are described by a constant redshift function and generalizes the standard flat Friedmann-Robertson-Walker spacetime. The polytropic equation of state allows us to consider in (3+1)(3+1)-dimensions generalizations of the phantom energy and the generalized Chaplygin gas sources.Comment: 6 pages, 2 figures, accepted for publication in European Physical Journal

    Geometrically nonlinear Cosserat elasticity in the plane: applications to chirality

    Get PDF
    Modelling two-dimensional chiral materials is a challenging problem in continuum mechanics because three-dimensional theories reduced to isotropic two-dimensional problems become non-chiral. Various approaches have been suggested to overcome this problem. We propose a new approach to this problem by formulating an intrinsically two-dimensional model which does not require references to a higher dimensional one. We are able to model planar chiral materials starting from a geometrically non-linear Cosserat type elasticity theory. Our results are in agreement with previously derived equations of motion but can contain additional terms due to our non-linear approach. Plane wave solutions are briefly discussed within this model.Comment: 22 pages, 1 figure; v2 updated versio

    New classes of modified teleparallel gravity models

    Get PDF
    New classes of modified teleparallel theories of gravity are introduced. The action of this theory is constructed to be a function of the irreducible parts of torsion f(Tax,Tten,Tvec)f(T_{\rm ax},T_{\rm ten},T_{\rm vec}), where Tax,TtenT_{\rm ax},T_{\rm ten} and TvecT_{\rm vec} are squares of the axial, tensor and vector components of torsion, respectively. This is the most general (well-motivated) second order teleparallel theory of gravity that can be constructed from the torsion tensor. Different particular second order theories can be recovered from this theory such as new general relativity, conformal teleparallel gravity or f(T)f(T) gravity. Additionally, the boundary term BB which connects the Ricci scalar with the torsion scalar via R=T+BR=-T+B can also be incorporated into the action. By performing a conformal transformation, it is shown that the two unique theories which have an Einstein frame are either the teleparallel equivalent of general relativity or f(T+B)=f(R)f(-T+B)=f(R) gravity, as expected.Comment: v2: 10 pages, accepted for publication in PLB; for a detailed derivation of the field equations see Appendix A in v
    corecore