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Register a new userStability of the Ellis-Bronnikov-Morris-Thorne Wormhole
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Added by
Alexander Shatskiy Dr.
Publication date
2009
fields
Physics
and research's language is
English
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The stability of one type of the static Ellis-Bronnikov-Morris-Thorne wormholes is considered. These wormholes filled with radial magnetic field and phantom dust with a negative energy density.
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We consider the wormhole of Ellis, Bronnikov, Morris and Thorne (EBMT), arising from Einsteins equations in presence of a phantom scalar field. In this paper we propose a simplified derivation of the linear instability of this system, making comparisons with previous works on this subject (and generalizations) by Gonzalez, Guzman, Sarbach, Bronnikov, Fabris and Zhidenko.
In this paper, we investigate the simplest wormhole solution - the Ellis-Bronnikov one - in the context of the Asymptotically Safe Gravity (ASG) at the Planck scale. We work with three models, which employ Ricci scalar, Kretschmann scalar, and squared Ricci tensor to improve the field equations by turning the Newton constant into a running coupling constant. For all the cases, we check the radial energy conditions of the wormhole solution and compare them with those valid in General Relativity (GR). We verify that asymptotic safety guarantees that the Ellis-Bronnikov wormhole can satisfy the radial energy conditions at the throat radius, $r_0$, within an interval of values of this latter. That is quite different from the result found in GR. Following, we evaluate the effective radial state parameter, $omega(r)$, at $r_0$, showing that the quantum gravitational effects modify Einsteins field equations in such a way that it is necessary a very exotic source of matter to generate the wormhole spacetime -- phantom or quintessence-like. That occurs within some ranges of throat radii, even though the energy conditions are or not violated there. Finally, we find that, although at $r_0$ we have a quintessence-like matter, on growing of $r$ we necessarily come across phantom-like regions. We speculate if such a phantom fluid must always be present in wormholes in the ASG context or even in more general quantum gravity scenarios.
In the Ellis wormhole metrics we study characteristics of fluid dynamics and the properties of linear sound waves. By implying the energy-momentum equation and the continuity equation in the general relativistic manner we examine the flow dynamics and solve the corresponding equations for a relatively simple case - radial flow. To study the linear sound waves the equations governing the mentioned physical system are linearized and solved and interesting characteristic properties are found.
We analyze the properties of the circular orbits for massive particles in the equatorial plane of symmetric rotating Ellis wormholes. In particular, we obtain the orbital frequencies and the radial and vertical epicyclic frequencies, and consider their lowest parametric, forced and Keplerian resonances. These show that quasi-periodic oscillations in accretion disks around symmetric rotating Ellis wormholes have many distinct properties as compared to quasi-periodic oscillations in accretion disks around rotating Teo wormholes and the Kerr black hole. Still we can distinguish some common features which appear in wormhole spacetimes as opposed to black holes. The most significant ones include the possibility of excitation of stronger resonances such as lower order parametric and forced resonances and the localization of these resonances deep in the region of strong gravitational interaction near the wormhole throat, which will lead to further amplification of the signal.
Stable massless wormholes are theoretically interesting in their own right as well as for astrophysical applications, especially as galactic halo objects. Therefore, the study of gravitational lensing observables for such objects is of importance, and we do here by applying the parametric post-Newtonian method of Keeton and Petters to massless dyonic charged wormholes of the Einstein-Maxwell-Dilaton field theory and to the massless Ellis wormhole of the Einstein minimally coupled scalar field theory. The paper exemplifies how the lensing signatures of two different solutions belonging to two different theories could be qualitatively similar from the observational point of view. Quantitative differences appear depending on the parameter values. Surprisingly, there appears an unexpected divergence in the correction to differential time delay, which seems to call for a review of its original derivation.
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