6 research outputs found
Rotation and twist regular modes for trapped ghosts
A parameter-independent notion of stationary slow motion is formulated then
applied to the case of stationary rotation of massless trapped ghosts. The
excitations correspond to a rotation mode with angular momentum and
twist modes. It is found that the rotation mode, which has no parity, causes
excess in the angular velocity of dragged distant coordinate frames in one
sheet of the wormhole while in the other sheet the angular velocity of the
ghosts is that of rotating stars: . As to the twist modes, which all
have parity, they cause excess in the angular velocity of one of the throat's
poles with respect to the other.Comment: 11 pages, 3 figures; General Relativity and Gravitation - 201
Wormhole Geometries In Gravity
We study wormhole solutions in the framework of f (R,T) gravity where R is
the scalar curvature, and T is the trace of the stress-energy tensor of the
matter. We have obtained the shape function of the wormhole by specifying an
equation of state for the matter field and imposing the flaring out condition
at the throat. We show that in this modified gravity scenario, the matter
threading the wormhole may satisfy the energy conditions, so it is the
effective stress-energy that is responsible for violation of the null energy
condition.Comment: 9 pages, 4 figures, published version, references adde
Electromagnetic Fields and Charged Particle Motion Around Magnetized Wormholes
We perform a study to describe motion of charged particles under the
influence of electromagnetic and gravitational fields of a slowly rotating
wormhole with nonvanishing magnetic moment. We present analytic expression for
potentials of electromagnetic field for an axially symmetric slowly rotating
magnetized wormholes. While addressing important issues regarding the subject,
we compare our results of motion around black holes and wormholes in terms of
the ratio of radii of event horizons of a black hole and of the throat of a
wormhole. It is shown that both radial and circular motions of test bodies in
the vicinity of a magnetized wormhole could give rise to a peculiar
observational astrophysical phenomenon.Comment: 9 pages, 4 figures, 2 tables, accepted for publication in
Astrophysics & Space Scienc
Magnetized dusty black holes and wormholes
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 τ0 (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
Magnetized dusty black holes and wormholes
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 τ0 (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. © 2021 by the authors. Licensee MDPI, Basel, Switzerland