We present a family of static and evolving spherically symmetric Lorentzian wormhole solutions in N+1 dimensional Einstein gravity. In general, for static wormholes, we require that at least the radial pressure has a barotropic equation of state of the form pr = ωrρ, where the state parameter ωr is constant. On the other hand, it is shown that in any dimension N ≥ 3, with φ(r) = Λ = 0 and anisotropic barotropic pressure with constant state parameters, static wormhole configurations are always asymptotically flat spacetimes, while in 2+1 gravity there are not only asymptotically flat static wormholes and also more general ones. In this case, the matter sustaining the three-dimensional wormhole may be only a pressureless fluid. In the case of evolving wormholes with N ≥ 3, the presence of a cosmological constant leads to an expansion or contraction of the wormhole configurations: for positive cosmological constant we have wormholes which expand forever and, for negative cosmological constant we have wormholes which expand to a maximum value and then recollapse. In the absence of a cosmological constant the wormhole expands with constant velocity, i.e without acceleration or deceleration. In 2+1 dimensions the expanding wormholes always have an isotropic and homogeneous pressure, depending only on the time coordinate.
We investigate a family of inhomogeneous and anisotropic gravitational fields exhibiting a future singularity at a finite value of the proper time. The studied spherically symmetric spacetimes are asymptotically Friedmann-Robertson-Walker at spatial infinity and describe wormhole configurations filled with two matter components: one inhomogeneous and anisotropic fluid and another isotropic and homogeneously distributed fluid, characterized by the supernegative equation of state ω = p/ρ < −1. In previously constructed wormholes, the notion of the phantom energy was used in a more extended sense than in cosmology, where the phantom energy is considered a homogeneously distributed fluid. Specifically, for some static wormhole geometries the phantom matter was considered as an inhomogeneous and anisotropic fluid, with radial and lateral pressures satisfying the relations pr/ρ < −1 and p l = pr, respectively. In this paper we construct phantom evolving wormhole models filled with an isotropic and homogeneous component, described by a barotropic or viscous phantom energy, and ending in a big rip singularity. In two of considered cases the equation of state parameter is constrained to be less than −1, while in the third model the finite-time future singularity may occur for ω < −1, as well as for −1 < ω ≤ 1.
Extending the results of our previous work we construct an uniparametric class of action principles for complex scalar fields with the property that their energy momentum tensor and the electric current vanish for certain massive configurations. These stealth fields do not curve the spacetime and they do not source electromagnetic fields in spite their non-trivial degrees of freedom and U p1q gauge invariance. We shall also show that the presence of these stealth fields can affect the strength of the gravity-matter and radiation-matter coupling of other massive configurations. Indeed, the energy momentum tensor of other massive (non-stealth) configurations and the electric current can be rescaled (with a stealth-mass depending factor) with respect to the predictions of the standard complex scalar field model. Hence we argue that stealth fields could be detected indirectly by means of their effects on standard configurations of matter.
We construct a generic class of models for complex scalar fields — minimally coupled to gravity and electromagnetism — with the property that their energy-momentum tensor and the electric current vanish for certain massive configurations. These are electromagnetically and gravitationally stealth fields. We shall see that the latter configurations can affect, in addition, the strength of the gravity-matter and electromagnetic-matter couplings of other (non-stealth) modes present in the system, which turn out to be equivalent to the re-scaling the electric charge and the Newton constant (with a stealth-mass depending factor).
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