Search results for "Wormhole"
showing 10 items of 33 documents
Nonsingular electrovacuum solutions with dynamically generated cosmological constant
2013
We consider static spherically symmetric configurations in a Palatini extension of General Relativity including R-2 and Ricci-squared terms, which is known to replace the central singularity by a wormhole in the electrovacuum case. We modify the matter sector of the theory by adding to the usual Maxwell term a nonlinear electromagnetic extension which is known to implement a confinement mechanism in flat space. One feature of the resulting theory is that the nonlinear electric field leads to a dynamically generated cosmological constant. We show that with this matter source the solutions of the model are asymptotically de Sitter and possess a wormhole topology. We discuss in some detail the…
Melvin Universe in Born-Infeld gravity
2015
We consider a magnetic flux pointing in the $z$ direction of an axially symmetric space-time (Melvin Universe) in a Born-Infeld-type extension of General Relativity (GR) formulated in the Palatini approach. Large magnetic fields could have been produced in the early Universe, and given rise to interesting phenomenology regarding wormholes and black hole remnants. We find a formal analytic solution to this problem that recovers the GR result in the appropriate limits. Our results set the basis for further extensions that could allow the embedding of pairs of black hole remnants in geometries with intense magnetic fields.
Geodesic completeness in a wormhole spacetime with horizons
2015
The geometry of a spacetime containing a wormhole generated by a spherically symmetric electric field is investigated in detail. These solutions arise in high-energy extensions of General Relativity formulated within the Palatini approach and coupled to Maxwell electrodynamics. Even though curvature divergences generically arise at the wormhole throat, we find that these spacetimes are geodesically complete. This provides an explicit example where curvature divergences do not imply spacetime singularities.
Impact of curvature divergences on physical observers in a wormhole space-time with horizons
2016
The impact of curvature divergences on physical observers in a black hole space-time which, nonetheless, is geodesically complete is investigated. This space-time is an exact solution of certain extensions of General Relativity coupled to Maxwell's electrodynamics and, roughly speaking, consists on two Reissner-Nordstr\"{o}m (or Schwarzschild or Minkowski) geometries connected by a spherical wormhole near the center. We find that, despite the existence of infinite tidal forces, causal contact is never lost among the elements making up the observer. This suggests that curvature divergences may not be as pathological as traditionally thought.
The quantum, the geon, and the crystal
2015
Effective geometries arising from a hypothetical discrete structure of space-time can play an important role in the understanding of the gravitational physics beyond General Relativity. To discuss this question, we make use of lessons from crystalline systems within solid state physics, where the presence of defects in the discrete microstructure of the crystal determine the kind of effective geometry needed to properly describe the system in the macroscopic continuum limit. In this work we study metric-affine theories with non-metricity and torsion, which are the gravitational analog of crystalline structures with point defects and dislocations. We consider a crystal-motivated gravitationa…
Non-Riemannian geometry: towards new avenues for the physics of modified gravity
2015
Less explored than their metric (Riemannian) counterparts, metric-affine (or Palatini) theories bring an unexpected phenomenology for gravitational physics beyond General Relativity. Lessons of crystalline structures, where the presence of defects in their microstructure requires the use of non-Riemannian geometry for the proper description of their properties in the macroscopic continuum level, are discussed. In this analogy, concepts such as wormholes and geons play a fundamental role. Applications of the metric-affine formalism developed by the authors in the last three years are reviewed.
Geometric aspects of charged black holes in Palatini theories
2015
Charged black holes in gravity theories in the Palatini formalism present a number of unique properties. Their innermost structure is topologically nontrivial, representing a wormhole supported by a sourceless electric flux. For certain values of their effective mass and charge curvature divergences may be absent, and their event horizon may also disappear yielding a remnant. We give an overview of the mathematical derivation of these solutions and discuss their geodesic structure and other geometric properties.
Particle creation by wormholes: A 1 + 1 model
2020
The propagation of a free massless scalar field in a [Formula: see text]-dimensional Minkowski space modeling, a wormhole is considered. The wormhole model consists on two timelike trajectories, which represent the entrance and the exit of the wormhole, connected via some transfer function that specifies how incoming modes that reach the entrance are transferred to the exit. We find that particles and energy fluxes are generically produced except for transfer functions that represent global conformal transformations. We consider several examples involving exit trajectories which are asymptotically inertial, asymptotically null, and also involving a faster-than-light motion to illustrate th…
A Lemaitre-Tolman-Bondi cosmological wormhole
2010
We present a new analytical solution of the Einstein field equations describing a wormhole shell of zero thickness joining two Lema{\i}tre-Tolman-Bondi universes, with no radial accretion. The material on the shell satisfies the energy conditions and, at late times, the shell becomes comoving with the dust-dominated cosmic substratum.
The Anti-de Sitter Gott Universe: A Rotating BTZ Wormhole
1999
Recently it has been shown that a 2+1 dimensional black hole can be created by a collapse of two colliding massless particles in otherwise empty anti-de Sitter space. Here we generalize this construction to the case of a non-zero impact parameter. The resulting spacetime, which may be regarded as a Gott universe in anti-de Sitter background, contains closed timelike curves. By treating these as singular we are able to interpret our solution as a rotating black hole, hence providing a link between the Gott universe and the BTZ black hole. When analyzing the spacetime we see how the full causal structure of the interior can be almost completely inferred just from considerations of the conform…