General class of wormhole geometries in conformal Weyl gravity

Classical and Quantum Gravity (Impact Factor: 3.1). 02/2008; 25(2008):175006. DOI: 10.1088/0264-9381/25/17/175006
Source: arXiv

ABSTRACT 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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    • "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.
    Journal of Cosmology and Astroparticle Physics 07/2014; 11(2014):007. DOI:10.1088/1475-7516/2014/11/007 · 5.88 Impact Factor
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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.
    General Relativity and Gravitation 08/2012; 45(2). DOI:10.1007/s10714-012-1478-5 · 1.73 Impact Factor
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    • "In the context of nonlinear electrodynamics, it was found that certain dynamic wormhole solutions obey (suitably defined versions of) the WEC [18]. It is interesting to note that in modified theories of gravity, more specifically in f (R) gravity, the matter threading the wormhole throat can be forced to obey (suitably defined versions of) all the energy conditions, and it is the higher-order curvature terms that are responsible for supporting these wormhole geometries [19]. (Related issues arise when scalar fields are conformally coupled to gravity [20] [21].) "
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    ABSTRACT: We consider the construction of generic spherically symmetric thin-shell traversable wormhole spacetimes in standard general relativity. By using the cut-and-paste procedure, we comprehensively analyze the stability of arbitrary spherically symmetric thin-shell wormholes to linearized spherically symmetric perturbations around static solutions. While a number of special cases have previously been dealt with in scattered parts of the literature, herein we take considerable effort to make the analysis as general and unified as practicable. We demonstrate in full generality that stability of the wormhole is equivalent to choosing suitable properties for the exotic material residing on the wormhole throat.
    Physical Review D 12/2011; 86(2012):044026. DOI:10.1103/PhysRevD.86.044026 · 4.86 Impact Factor
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