Quantization of minisuperspaces as ordinary gauge systems

Simple cosmological models are used to show that gravitation can be quantized as an ordinary gauge system if the Hamilton-Jacobi equation for the model under consideration is separable. In this situation, a canonical transformation can be performed such that in terms of the new variables the model has a linear and homogeneous constraint, and therefore canonical gauges are admissible in the path integral. This has the additional practical advantage that gauge conditions that do not generate Gribov copies are then easy to choose.Comment: 12 page

Addendum to "Thin-shell wormholes supported by ordinary matter in Einstein-Gauss-Bonnet gravity"

Thin-shell wormholes are constructed starting from the exotic branch of Wiltshire spherically symmetric solution of Einstein-Gauss-Bonnet gravity. The energy-momentum tensor of the shell is studied, and it is shown that configurations supported by matter satisfying the energy conditions exist for certain values of the parameters. Differing from the previous result associated to the normal branch of Wiltshire solution, this is achieved for small positive values of the Gauss-Bonnet parameter and for vanishing charge.Comment: 8 pages, 2 figures; published in Phys. Rev. D (2011). Addendum to arXiv:0710.2041v3[gr-qc] (Phys. Rev. D {\bf 76}, 087502 (2007); D {\bf 77}, 089903(E) (2008)

Some aspects of cylindrical solutions in Brans-Dicke gravity

Several points regarding cylindrical Brans-Dicke geometries are studied. The issue of particle trajectories for the vacuum cylindrical solution is revisited. The possible particular nature of a global string metric is analysed. The general form of the junction conditions for matching cylindrical solutions within this theory is written down, and the relation with the general relativity limit is discussed.Comment: 7 page

Some general aspects of thin-shell wormholes with cylindrical symmetry

In this article we study a general class of non-rotating thin-shell wormholes with cylindrical symmetry. We consider two physically sound definitions of the flare-out condition and we show that the less restrictive one allows for the construction of wormholes with positive energy density at the throat. We also analyze the mechanical stability of these objects under perturbations preserving the symmetry, proving that previous results are particular cases of a general property. We present examples of wormholes corresponding to Einstein-Maxwell spacetimes.Comment: 9 pages, 2 figures; v4: corrected versio

Charged shells in a (2+1)-dimensional spacetime

We study circular shells in a (2+1)-dimensional background within the framework of Einstein-Born-Infeld theory. For shells around black holes we analyze the mechanical stability under perturbations preserving the symmetry. Shells around vacuum are also discussed. We find a large range in the values of the parameters compatible with stable configurations.Comment: 10 pages, 6 figures; v2: improved version, new references adde

Asymptotically anti-de Sitter cylindrical thin-shell wormholes

In this article we investigate cylindrical thin-shell wormholes which are asymptotically anti-de Sitter. We analyze their stability under perturbations preserving the symmetry by using two different methods. We compare the results with those corresponding to the wormholes constructed from the Levi-Civita spacetime. We find that the configurations always require the presence of exotic matter at the throat, and, in the case of the linearized stability analysis, they can be stable for suitable values of the parametersComment: 11 pages, 3 figures; v2: improved versio