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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    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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    ABSTRACT: In this work, we consider the possibility of expanding wormholes in higher-dimensions, which is an important ingredient of modern theories of fundamental physics. An important motivation is that non-trivial topological objects such as microscopic wormholes may have been enlarged to macroscopic sizes in an expanding inflationary cosmological background. Since the Ricci scalar is only a function of time in standard cosmological models, we use this property as a simplifying assumption. More specifically, we consider a particular class of wormhole solutions corresponding to the choice of a spatially homogeneous Ricci scalar. The possibility of obtaining solutions with normal and exotic matter is explored and we find a variety of solutions including those in four dimensions that satisfy the null energy condition (NEC) in specific time intervals. In particular, for five dimensions, we find solutions that satisfy the NEC throughout the respective evolution.
    Physical Review D 06/2014; 90(2014):024072. DOI:10.1103/PhysRevD.90.024072 · 4.69 Impact Factor
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    ABSTRACT: In this paper, we consider the problem of test particles and test scalar fields propagating on the background of a class of wormhole space-times. For test particles, we solve for arbitrary causal geodesics in terms of integrals which are solved numerically. These integrals are parametrized by the radius and shape of the wormhole throat as well as the initial conditions of the geodesic trajectory. In terms of these parameters, we compute the conditions for the geodesic to traverse the wormhole, to be reflected by the wormhole's potential or to be captured on an unstable bound orbit at the wormhole's throat. These causal geodesics are visualized by embedding plots in Euclidean space in cylindrical coordinates. For test scalar fields, we compute transmission coefficients and quasi-normal modes for arbitrary coupling of the field to the background geometry in the WKB approximation. We show that there always exists an unstable mode whenever the coupling constant is greater than 1/2. This analysis is interesting since recent computations of self-interactions of a static scalar field in wormhole space-times reveal some anomalous dependence on the coupling constant, principally, the existence of an infinite discrete set of poles. We show that this pathological behavior of the self-field is an artifact of computing the interaction for values of the coupling constant that do not lie in the domain of stability.
    Physical Review D 04/2014; 90(2). DOI:10.1103/PhysRevD.90.024057 · 4.86 Impact Factor

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