Conveners
Wormholes, energy conditions and time machines: Thursday block 1
- Francisco Lobo (Science Faculty of the University of Lisbon)
Wormholes, energy conditions and time machines: Thursday block 2
- Francisco Lobo (Science Faculty of the University of Lisbon)
Wormholes, energy conditions and time machines: Friday block 1
- Francisco Lobo (Science Faculty of the University of Lisbon)
Wormholes, energy conditions and time machines: Friday block 2
- Francisco Lobo (Science Faculty of the University of Lisbon)
Description
The General Theory of Relativity has been an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes, gravitational radiation to the cosmological models, predicting a primordial beginning, namely the big-bang. All these solutions have been obtained by first considering a plausible distribution of matter, and through the Einstein field equation, the spacetime metric of the geometry is determined. However, one may solve the Einstein field equation in the reverse direction, namely, one first considers an interesting and exotic spacetime metric, then finds the matter source responsible for the respective geometry. In this manner, it was found that some of these solutions possess a peculiar property, namely 'exotic matter,' involving a stress-energy tensor that violates the null energy condition. These geometries also allow closed timelike curves, with the respective causality violations. These solutions are primarily useful as 'gedanken-experiments' and as a theoretician's probe of the foundations of general relativity, and include traversable wormholes and superluminal 'warp drive' spacetimes. In this parallel session, in addition to extensively exploring interesting features, in particular, the physical properties and characteristics of these 'exotic spacetimes,' we also explore other non-trivial general relativistic geometries that generate closed timelike curves.
It is known that all wormholes violate classical energy conditions, non-negativity constraints on contractions of the stress-energy tensor. Since these conditions are violated by quantum fields, it was believed that wormholes can be constructed in the context of semiclassical gravity. But negative energies in quantum field theory are not without restriction: quantum energy inequalities (QEIs)...
We describe the connection between a traversable wormhole and the Casimir effect. With the help of an equation of state we also discuss different forms of solutions related to the Casimir source. The effect of including an electromagnetic field and a temperature to the original energy density are also discussed.
In 2006 we proposed the conjecture that rotating wormholes might be stable, while static ones might not be. In this talk we present an exact solution of the Einstein-Phantom Field equations similar to the Kerr solution. It is singular in a ring around the throat, but this singularity is geodesically complete and cannot be touched by null geodesics, our conclusion is that the singularity is not...
In this talk the possible geodesic completeness of an electromagnetic dipole wormhole is studied in detail. The space-time contains a curvature singularity, and belongs to a class of solutions to the Einstein-Maxwell equations with a coupled scalar field that can be allowed to be phantom or dilatonic. Specifically, a numerical analysis is performed to examine congruences of null geodesics that...
In this talk we will present the first study of the spectrum of quasinormal modes of rotating Ellis-Bronnikov wormholes. We compute the spectrum using a spectral decomposition of the metric perturbations on a numerical background. We study the dependence of the modes on the angular momentum and show that rotation breaks the triple isospectrality of the symmetric and static wormhole.
It has been long known that the static Ellis-Bronnikov wormholes of GR are radially unstable. Here we study the radial perturbations of these wormholes in slow rotation up to second order. We find that rotation can potentially stabilize the unstable mode of the static wormholes.
This work explores the environmental influences on wormholes. Specifically, two classes of wormholes are considered: the Damour-Solodukhin and braneworld types. I will discuss the Damour-Solodukhin wormhole at the galactic center. Our results suggest that galactic Damour-Solodukhin wormholes are more stable than isolated ones under linear scalar perturbation. This enables the identification of...
In this work we analyze traversable wormhole spacetimes in the framework of a covariant generalization of Einstein's General Relativity known as energy-momentum squared gravity. Here, we show that a wide variety of wormhole solutions for which the matter fields satisfy all the energy conditions, namely the null, weak, strong and dominant energy conditions, exist in this framework, without the...
We consider the torsional completion of the theory of gravity in which torsion is a propagating axial-vector field: we show how this changes the energy conditions leading to the singularity formation being avoided. We discuss how the same construction possesses regular matter distributions even in the case of a single particle. We give a brief discussion also about the localization of such...
We find that a field with oscillations of matter in proper time has the properties of a zero-spin bosonic field. A particle observed in this field is a proper time oscillator. Neglecting all quantum effects, a proper time oscillator can mimic a point mass at rest in general relativity. The spacetime outside a 'stationary' proper time oscillator is a Schwarzschild field.
Regular black holes have become a popular alternative to the singular mathematical black holes predicted by general relativity as they circumvent mathematical pathologies associated with the singularity while preserving crucial black hole features such as the trapping of light. Based on the assumption that semiclassical gravity is valid in the vicinity of their apparent horizons, we examine...
Two broad sets of classes of gravitational field propulsion techniques are investigated: classical general relativity field propulsion, and the quantum manipulation of spacetime. Classical approaches in this paper include a Forward Coil, which concentrates an acceleration field in the center of the coil, the use of wormholes, and a tokamak plasma quadrupole oscillator, creating gravitational...
In this presentation, I will discuss about the unhindered gravitational collapse of spatially homogeneous (SH) scalar fields $\phi$ with a potential $V_{s}(\phi)$, as well as vector fields $\tilde{A}$ with a potential $V_{v}(B)$ where $B=g(\tilde{A},\tilde{A})$ and $g$ is the metric tensor. If the past end-point of a causal geodesic is a singularity, then this singularity is said to be naked....
We have systematically presented the effect of the Generalized Uncertainty Principle (GUP) in Casimir wormhole space-time in the recently proposed modified gravity, the so-called symmetric teleparallel gravity, or $f(Q)$ gravity. We consider two famous GUP models, such as the Kempf, Mangano, and Mann (KMM) model and the Detournay, Gabriel, and Spindel (DGS) model, in this study. Also, to find...
