General class of wormhole geometries in conformal Weyl gravity

Classical and Quantum Gravity (Impact Factor: 3.17). 02/2008; 25(2008):175006. DOI: 10.1088/0264-9381/25/17/175006
Source: arXiv


In this work, a general class of wormhole geometries in conformal Weyl gravity is analyzed. A wide variety of exact solutions of asymptotically flat spacetimes is found, in which the stress energy tensor profile differs radically from its general relativistic counterpart. In particular, a class of geometries is constructed that satisfies the energy conditions in the throat neighborhood, which is in clear contrast to the general relativistic solutions.

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Available from: Francisco S. N. Lobo, Nov 13, 2012
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    • "Lobo and Oliveira took f (R) gravity as an example and suggested that modified gravities provide another possibility to support traversable wormholes [15]: it is the generalized energy conditions that are violated, while the standard energy conditions as in GR may remain valid. To date, their proposal has been applied to exact solutions of the Morris-Thorne-type wormholes in various modified gravities, such as the Weyl conformal [16], vacuum Brans-Dicke [17], modified teleparralel [18], hybrid metric-Palatini f (R) [19], and Einstein-Gauss-Bonnet gravities [20]. "
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    ABSTRACT: Following the recent theory of Lovelock-Brans-Dicke gravity, we continue to investigate the conditions to support traversable wormholes by the gravitational effects of spacetime parity and topology, which arise from the nonminimal couplings of a background scalar field with the Chern-Pontryagin density and the Gauss-Bonnet invariant. The flaring-out condition indicates that a Morris-Thorne-type wormhole can be maintained by violating the generalized null energy conditions, and thus also breaking down the generalized weak, strong, and dominant energy conditions. Meanwhile, the standard energy conditions in general relativity may still be respected by the classical matter fields. To meet these requirements, the two topological effects have to dominate over the other sources of gravity, and the scalar field is preferred to be noncanonical.
    Preview · Article · Aug 2015
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    • "In fact, in the context of modified gravity it was shown that one may impose that the matter threading the wormhole satisfies the energy conditions, so that it is the effective stress-energy tensor containing higher order curvature derivatives that is responsible for the NEC violation. Thus, the higher order curvature terms, interpreted as a gravitational fluid, sustain these non-standard wormhole geometries, fundamentally different from their counterparts in general relativity [57] [58] [59] [60] [61] [62] [63] [64] [65]. "
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    ABSTRACT: We consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. More specifically, we consider an equation of state in which the sum of the energy density and radial pressure is proportional to a constant with a value smaller than that of the inverse area characterising the system, i.e., the area of the wormhole mouth. This approach is motivated by a recently proposed cosmological event, denoted "the little sibling of the big rip", where the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not [1]. By using the cut-and-paste approach, we match interior spherically symmetric wormhole solutions to an exterior Schwarzschild geometry, and analyze the stability of the thin-shell to linearized spherically symmetric perturbations around static solutions, by choosing suitable properties for the exotic material residing on the junction interface radius. Furthermore, we also consider an inhomogeneous generalisation of the equation of state considered above and analyse the respective stability regions. In particular, we obtain a specific wormhole solution with an asymptotic behaviour corresponding to a global monopole.
    Full-text · Article · Jul 2014 · Journal of Cosmology and Astroparticle Physics
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    • ", [56], [57], [58], [59], [60], [61], [62], [63], [64], [65], and [66]. "
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    ABSTRACT: We classify the existent Birkhoff-type theorems into four classes: First, in field theory, the theorem states the absence of helicity 0- and spin 0-parts of the gravitational field. Second, in relativistic astrophysics, it is the statement that the gravitational far-field of a spherically symmetric star carries, apart from its mass, no information about the star; therefore, a radially oscillating star has a static gravitational far-field. Third, in mathematical physics, Birkhoff's theorem reads: up to singular exceptions of measure zero, the spherically symmetric solutions of Einstein's vacuum field equation with Lambda = 0 can be expressed by the Schwarzschild metric; for Lambda unequal 0, it is the Schwarzschild-de Sitter metric instead. Fourth, in differential geometry, any statement of the type: every member of a family of pseudo-Riemannian space-times has more isometries than expected from the original metric ansatz, carries the name Birkhoff-type theorem. Within the fourth of these classes we present some new results with further values of dimension and signature of the related spaces; including them are some counterexamples: families of space-times where no Birkhoff-type theorem is valid. These counterexamples further confirm the conjecture, that the Birkhoff-type theorems have their origin in the property, that the two eigenvalues of the Ricci tensor of two-dimensional pseudo-Riemannian spaces always coincide, a property not having an analogy in higher dimensions. Hence, Birkhoff-type theorems exist only for those physical situations which are reducible to two dimensions.
    Full-text · Article · Aug 2012 · General Relativity and Gravitation
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