Rotating Melvin-like Universes and Wormholes in General Relativity

Бронников, К. А.; Krechet, V. G.; Oshurko, V. B.

doi:10.3390/sym12081306

Cited by 20 publications

(13 citation statements)

References 129 publications

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“…It is easy to notice that all potentials in the stringlike solutions have a changing sign, in agreement with ( 45) and (51). Additionally, in the canonical sector, the potential close to the axis has an attracting nature.…”

Section: The Phantom Sector N = −1supporting

confidence: 85%

“…Equations (45) and (51) implying that stringlike solutions cannot be obtained with purely nonpositive or purely nonnegative potentials.…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that the existence of wormholes in GR, in general, requires some amount of "exotic" matter violating the standard (Weak and Null) energy conditions, and its necessity can be avoided either in alternative theories of gravity (see [47,48] for reviews) or within general relativity in cylindrical symmetry by invoking rotation and an appropriate choice of matter sources [49][50][51]. In this respect, we can note that HMPG, being a purely geometric source of scalar fields, both canonical and phantom, can provide a natural framework for wormhole construction without other "exotic" sources.…”

mentioning

confidence: 99%

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Hybrid Metric-Palatini Gravity: Regular Stringlike Configurations

2020

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We discuss static, cylindrically symmetric vacuum solutions of hybrid metric-Palatini gravity (HMPG), a recently proposed theory that has been shown to successfully pass the local observational tests and produce a certain progress in cosmology. We use HMPG in its well-known scalar-tensor representation. The latter coincides with general relativity containing, as a source of gravity, a conformally coupled scalar field ϕ and a self-interaction potential V(ϕ). The ϕ field can be canonical or phantom, and, accordingly, the theory splits into canonical and phantom sectors. We seek solitonic (stringlike) vacuum solutions of HMPG, that is, completely regular solutions with Minkowski metric far from the symmetry axis, with a possible angular deficit. A transition of the theory to the Einstein conformal frame is used as a tool, and many of the results apply to the general Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories as well as f(R) theories of gravity. One of these results is a one-to-one correspondence between stringlike solutions in the Einstein and Jordan frames if the conformal factor that connects them is everywhere regular. An algorithm for the construction of stringlike solutions in HMPG and scalar-tensor theories is suggested, and some examples of such solutions are obtained and discussed.

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Section: The Phantom Sector N = −1supporting

confidence: 85%

“…Equations (45) and (51) implying that stringlike solutions cannot be obtained with purely nonpositive or purely nonnegative potentials.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Hybrid Metric-Palatini Gravity: Regular Stringlike Configurations

2020

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“…We consider photons (or light rays) that move radially in the direction from the region R > 0 to the region R < 0, which corresponds to the minus sign in the second term in (44). For motion in the opposite direction, one should replace R → −R in Eq.…”

Section: Photon Motion Across the Dust Layermentioning

confidence: 99%

“…Rotational degrees of freedom are apparently able to replace exotic matter at wormhole construction. At least, some examples of rotating cylindrically symmetric wormhole models in GR have been built without NEC violation [42][43][44]; the recent examples with a static metric [19,20] contain a Dirac field involving spin; one can also mention exotic-free solutions in the Einstein-Cartan theory [45,46] containing nonzero torsion.…”

Section: Introductionmentioning

confidence: 99%

Magnetized dusty black holes and wormholes

Бронников¹,

Kashargin²,

Sushkov³

2021

Preprint

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We consider the generalized Tolman solution of general relativity, describing the evolution of a spherical dust cloud in the presence of an external electric or magnetic field. The solution contains three arbitrary functions f (R) , F (R) and τ 0 (R) , where R is a radial coordinate in the comoving reference frame. The solution splits into three branches corresponding to hyperbolic (f > 0 ), parabolic ( f = 0 ) and elliptic (f < 0 ) types of motion. In such models, we study the possible existence of wormhole throats defined as spheres of minimum radius at a fixed time instant, and prove the existence of throats in the elliptic branch under certain conditions imposed on the arbitrary functions. It is further shown that the normal to a throat is a timelike vector (except for the instant of maximum expansion, when this vector is null), hence a throat is in general located in a T-region of space-time. Thus if such a dust cloud is placed between two empty (Reissner-Nordström or Schwarzschild) space-time regions, the whole configuration is a black hole rather than a wormhole. However, dust clouds with throats can be inscribed into closed isotropic cosmological models filled with dust to form wormholes which exist for a finite period of time and experience expansion and contraction together with the corresponding cosmology. Explicit examples and numerical estimates are presented. The possible traversability of wormhole-like evolving dust layers is established by a numerical study of radial null geodesics.

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Traversable wormholes with double layer thin shells in quadratic gravity

2023

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In quadratic gravity, the junction conditions are six in number and permit the appearance of double layer thin shells. Double layers arise typically in theories with dipoles, i.e., two opposite charges, such as electromagnetic theories, and appear exceptionally in gravitational theories, which are theories with a single charge. We explore this property of the existence of double layers in quadratic gravity to find and study traversable wormholes in which the two domains of the wormhole interior region, where the throat is located, are matched to two vacuum domains of the exterior region via the use of two double layer thin shells. The quadratic gravity we use is essentially given by a $$R+\alpha R^2$$ R + α R 2 Lagragian, where R is the Ricci scalar of the spacetime and $$\alpha $$ α is a coupling constant, plus a matter Lagrangian. The null energy condition, or NEC for short, is tested for the whole wormhole spacetime. The analysis shows that the NEC is satisfied for the stress-energy tensor of the matter in the whole wormhole interior region, notably at the throat, and is satisfied for some of the stress–energy tensor components of the matter at the double layer thin shell, but is not satisfied for some other components, namely, the double layer stress–energy distribution component, at the thin shell. This seems to mean that the NEC is basically impossible, or at least very hard, to be satisfied when double layer thin shells are present. Single layer thin shells are also admitted within the theory, and we present thin shell traversable wormholes, i.e., wormholes without interior, with a single layer thin shell at the throat for which the corresponding stress–energy tensor satisfies the NEC, that are asymmetric, i.e., with two different vacuum domains of the exterior region joined at the wormhole throat.

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Rotating Melvin-like Universes and Wormholes in General Relativity

Cited by 20 publications

References 129 publications

Hybrid Metric-Palatini Gravity: Regular Stringlike Configurations

Hybrid Metric-Palatini Gravity: Regular Stringlike Configurations

Magnetized dusty black holes and wormholes

Traversable wormholes with double layer thin shells in quadratic gravity

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