Microscopic thin shell wormholes in magnetic Melvin universe

We construct thin shell wormholes in the magnetic Melvin universe. It is shown that in order to make a TSW in the Melvin spacetime the radius of the throat can not be larger than $\frac{2}{B_{0}}$ in which $B_{0}$ is the magnetic field constant. We also analyze the stability of the constructed wormhole in terms of a linear perturbation around the equilibrium point. In our stability analysis we scan a full set of the Equation of States such as Linear Gas, Chaplygin Gas, Generalized Chaplygin Gas, Modified Generalized Chaplygin Gas and Logarithmic Gas. Finally we extend our study to the wormhole solution in the unified Melvin and Bertotti-Robinson spacetime. In this extension we show that for some specific cases, the local energy density is partially positive but the total energy which supports the wormhole is positive.Comment: 8 pages, 6 figure

N-Dimensional non-abelian dilatonic, stable black holes and their Born-Infeld extension

We find large classes of non-asymptotically flat Einstein-Yang-Mills-Dilaton (EYMD) and Einstein-Yang-Mills-Born-Infeld-Dilaton (EYMBID) black holes in N-dimensional spherically symmetric spacetime expressed in terms of the quasilocal mass. Extension of the dilatonic YM solution to N-dimensions has been possible by employing the generalized Wu-Yang ansatz. Another metric ansatz, which aided in finding exact solutions is the functional dependence of the radius function on the dilaton field. These classes of black holes are stable against linear radial perturbations. In the limit of vanishing dilaton we obtain Bertotti-Robinson (BR) type metrics with the topology of $AdS_{2}\times S^{N-2}.$ Since connection can be established between dilaton and a scalar field of Brans-Dicke (BD) type we obtain black hole solutions also in the Brans-Dicke-Yang-Mills (BDYM) theory as well.Comment: 21 pages, no figures, to appear in in GR

Stability of thin-shell wormholes supported by ordinary matter in Einstein-Maxwell-Gauss-Bonnet gravity

Recently in (Phys. Rev. D 76, 087502 (2007) and Phys. Rev. D 77, 089903(E) (2008)) a thin-shell wormhole has been introduced in 5-dimensional Einstein-Maxwell-Gauss-Bonnet (EMGB) gravity which was supported by normal matter. We wish to consider this solution and investigate its stability. Our analysis shows that for the Gauss-Bonnet (GB) parameter $\alpha <0,$ stability regions form for a narrow band of finely-tuned mass and charge. For the case $\alpha >0$, we iterate once more that no stable, normal matter thin-shell wormhole exists.Comment: 11 pages, 4 figure

Higher dimensional thin-shell wormholes in Einstein-Yang-Mills-Gauss-Bonnet gravity

We present thin-shell wormhole solutions in Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory in higher dimensions d\geq5. Exact black hole solutions are employed for this purpose where the radius of thin-shell lies outside the event horizon. For some reasons the cases d=5 and d>5 are treated separately. The surface energy-momentum of the thin-shell creates surface pressures to resist against collapse and rendering stable wormholes possible. We test the stability of the wormholes against spherical perturbations through a linear energy-pressure relation and plot stability regions. Apart from this restricted stability we investigate the possibility of normal (i.e. non-exotic) matter which satisfies the energy conditions. For negative values of the Gauss-Bonnet (GB) parameter we obtain such physical wormholes.Comment: 9 pages, 6 figures. Dedicated to the memory of Rev. Ibrahim Eken (1927-2010) of Turke

New non-Abelian black hole solutions in Born-Infeld gravity

We introduce new black hole solutions to the Einstein-Yang-Mills-Born-Infeld (EYMBI), Einstein-Yang-Mills-Born-Infeld-Gauss-Bonnet (EYMBIGB) and Einstein-Yang-Mills-Born-Infeld-Gauss-Bonnet-Lovelock (EYMBIGBL) gravities in higher dimensions $N\geq 5$ to investigate the roles of Born-Infeld parameter $\beta$. It is shown that, these solutions in the limits of $\beta \to 0,$ and $\beta \to \infty ,$ represent pure gravity and gravity coupled with Yang-Mills fields, respectively. For $0<\beta <\infty$ it yields a variety of black holes, supporting even regular ones at $r=0$.Comment: 17 pages, 4 figures

d-dimensional non-asymptotically flat thin-shell wormholes in Einstein-Yang-Mills-Dilaton gravity

Thin-shell wormholes in Einstein-Yang-Mills-dilaton (EYMD) gravity are considered. We show that a non-asymptotically flat (NAF) black hole solution of the d-dimensional EYMD theory provides stable thin-shell wormholes which are supported entirely by exotic matter. The presence of dilaton makes the spacetime naturally NAF, and with our conclusion it remains still open to construct wormholes supported by normal matter between two such spacetimes.Comment: 6 pages, 5 figures. Title changed, the first version has been generalized to d-dimensions. The EYMGB part was removed and was considered in a more general form separately in arXiv:1007.462

Black hole and thin-shell wormhole solutions in Einstein-Hoffman-Born-Infeld theory

We employ an old field theory model, formulated and discussed by Born, Infeld, Hoffman and Rosen during 1930s. Our method of cutting-gluing of spacetimes resolves the double-valuedness in the displacement vector D(E), pointed out by these authors. A characteristic feature of their model is to contain a logarithmic term, and by bringing forth such a Lagrangian anew, we aim to attract the interest of field theorists to such a Lagrangian. We adopt the Hoffman-Born-Infeld (HBI) Lagrangian in general relativity to construct black holes and investigate the possibility of viable thin-shell wormholes. In particular, the stability of thin-shell wormholes supported by normal matter in 5-dimensional Einstein-HBI-Gauss-Bonnet gravity is highlighted.Comment: 17 pages, one figure, some constructive changes has been don