We briefly review the properties of static, spherically symmetric configurations of general relativity with a minimally coupled scalar field $\phi$ whose kinetic energy is negative in a restricted (strong-field) region of space and positive outside it [1--3]. This ``trapped ghost'' concept may in principle explain why no ghosts are observed under usual, weak-field conditions. The configurations considered are wormholes and regular black holes without a center, in particular, black universes (black holes with an expanding cosmology beyond the event horizon) [4--6]. Spherically symmetric perturbations of these objects are considered,
and it is stressed that, due to the universal shape of the effective potential near a transition surface from canonical to phantom behavior of the scalar field, such surfaces restrict the possible perturbations and play a stabilizing role.
 K.A. Bronnikov and S.V. Sushkov, “Trapped ghosts: a new class of wormholes,” Class. Quantum Grav. 27, 095022 (2010); arXiv: 1001.3511.
 K.A. Bronnikov and E.V. Donskoy, “Black universes with trapped ghosts.” Grav. Cosmol. 17, 176–180 (2011).
 K.A. Bronnikov, E.V. Donskoy, and P. Korolyov, “Magnetic wormholes and black universes with trapped ghosts,” Vestnik RUDN No. 2, 139–149 (2013).
 K.A.BronnikovandJ.C.Fabris,“Regularphantomblackholes,”Phys.Rev.Lett.96,251101 (2006); gr-qc/0511109.
 S.V. Bolokhov, K.A. Bronnikov, and M.V. Skvortsova, “Magnetic black universes and worm- holes with a phantom scalar,” Class. Quantum Grav. 29, 245006 (2012); arXiv: 1208.4619.
 K. A. Bronnikov and S. G. Rubin, Black Holes, Cosmology, and Extra Dimensions (World Scientific, Singapore, 2012).
|Type of contribution||Invited talk|