scholarly journals A self-sustained traversable scale-dependent wormhole

2018 ◽  
Vol 27 (09) ◽  
pp. 1850101 ◽  
Author(s):  
Ernesto Contreras ◽  
Pedro Bargueño

A self-sustained traversable wormhole is obtained as a vacuum solution of a scale-dependent gravitational theory. Comparisons with other approaches towards wormhole self-sustainability are presented with emphasis on the running of the gravitational coupling and on a possible effective description of gravity near the Planck scale.

Author(s):  
C. ROMERO ◽  
J. B. FONSECA-NETO ◽  
M. L. PUCHEU

We present the general theory of relativity in the language of a non-Riemannian geometry, namely, Weyl geometry. We show that the new mathematical formalism may lead to different pictures of the same gravitational phenomena, by making use of the concept of Weyl frames. We show that, in this formalism, it is possible to construct a scalar-tensor gravitational theory that is invariant with respect to the so-called Weyl tranformations and reduces to general relativity in a particular frame, the Riemann frame. In this approach the Weyl geometry plays a fundamental role since it appears as the natural geometrical setting of the theory when viewed in an arbitrary frame. Our starting point is to build an action that is manifestly invariant with respect to Weyl transformations. When this action is expressed in more familiar terms of Riemannian geometry we find that the theory has some similarities with Brans-Dicke theory of gravity. We illustrate this point with an example in which a known Brans-Dicke vacuum solution may appear when reinterpreted in a particular Weyl frame.


2009 ◽  
Vol 06 (03) ◽  
pp. 385-417 ◽  
Author(s):  
CARLOS CASTRO PERELMAN

We continue to study the Chern–Simons E8 Gauge theory of Gravity developed by the author which is a unified field theory (at the Planck scale) of a Lanczos–Lovelock Gravitational theory with a E8 Generalized Yang–Mills (GYM) field theory, and is defined in the 15D boundary of a 16D bulk space. The Exceptional E8 Geometry of the 256-dim slice of the 256 × 256-dimensional flat Clifford (16) space is explicitly constructed based on a spin connection [Formula: see text], that gauges the generalized Lorentz transformations in the tangent space of the 256-dim curved slice, and the 256 × 256 components of the vielbein field [Formula: see text], that gauge the nonabelian translations. Thus, in one-scoop, the vielbein [Formula: see text] encodes all of the 248 (nonabelian) E8 generators and 8 additional (abelian) translations associated with the vectorial parts of the generators of the diagonal subalgebra [Cl(8) ⊗ Cl(8)] diag ⊂ Cl(16). The generalized curvature, Ricci tensor, Ricci scalar, torsion, torsion vector and the Einstein–Hilbert–Cartan action is constructed. A preliminary analysis of how to construct a Clifford Superspace (that is far richer than ordinary superspace) based on orthogonal and symplectic Clifford algebras is presented. Finally, it is shown how an E8 ordinary Yang–Mills in 8D, after a sequence of symmetry breaking processes E8 → E7 → E6 → SO(8, 2), and performing a Kaluza–Klein–Batakis compactification on CP2, involving a nontrivial torsion, leads to a (Conformal) Gravity and Yang–Mills theory based on the Standard Model in 4D. The conclusion is devoted to explaining how Conformal (super) Gravity and (super) Yang–Mills theory in any dimension can be embedded into a (super) Clifford-algebra-valued gauge field theory.


2020 ◽  
Vol 35 (04) ◽  
pp. 2050016
Author(s):  
R. Moti ◽  
A. Shojai

Deriving the gravitational effective action directly from exact renormalization group is very complicated, if not impossible. Hence, to study the effects of running gravitational coupling which tends to a non-Gaussian UV fixed point (as it is supposed by the asymptotic safety conjecture), two steps are usually adopted. Cutoff identification and improvement of the gravitational coupling to the running one. As suggested in Ref. 1, a function of all independent curvature invariants seems to be the best choice for cutoff identification of gravitational quantum fluctuations in curved space–time and makes the action improvement, which saves the general covariance of theory, possible. Here, we choose Ricci tensor square for this purpose and then the equation of motion of improved gravitational action and its spherically symmetric vacuum solution are obtained. Indeed, its effect on the massive particles’ trajectory and the black hole thermodynamics is studied.


2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
P. Betzios ◽  
E. Kiritsis ◽  
V. Niarchos

Abstract We investigate emergent gravity extending the paradigm of the AdS/CFT correspondence. The emergent graviton is associated to the (dynamical) expectation value of the energy-momentum tensor. We derive the general effective description of such dynamics, and apply it to the case where a hidden theory generates gravity that is coupled to the Standard Model. In the linearized description, generically, such gravity is massive with the presence of an extra scalar degree of freedom. The propagators of both the spin-two and spin-zero modes are positive and well defined. The associated emergent gravitational theory is a bi-gravity theory, as is (secretly) the case in holography. The background metric on which the QFTs are defined, plays the role of dark energy and the emergent theory has always as a solution the original background metric. In the case where the hidden theory is holographic, the overall description yields a higher-dimensional bulk theory coupled to a brane. The effective graviton on the brane has four-dimensional characteristics both in the UV and IR and is always massive.


2011 ◽  
Vol 26 (22) ◽  
pp. 3721-3729 ◽  
Author(s):  
C. ROMERO ◽  
J. B. FONSECA-NETO ◽  
M. L. PUCHEU

We present the general theory of relativity in the language of a non-Riemannian geometry, namely, Weyl geometry. We show that the new mathematical formalism may lead to different pictures of the same gravitational phenomena, by making use of the concept of Weyl frames. We show that, in this formalism, it is possible to construct a scalar-tensor gravitational theory that is invariant with respect to the so-called Weyl tranformations and reduces to general relativity in a particular frame, the Riemann frame. In this approach the Weyl geometry plays a fundamental role since it appears as the natural geometrical setting of the theory when viewed in an arbitrary frame. Our starting point is to build an action that is manifestly invariant with respect to Weyl transformations. When this action is expressed in more familiar terms of Riemannian geometry we find that the theory has some similarities with Brans-Dicke theory of gravity. We illustrate this point with an example in which a known Brans-Dicke vacuum solution may appear when reinterpreted in a particular Weyl frame.


2006 ◽  
Vol 20 (07) ◽  
pp. 321-342 ◽  
Author(s):  
IGOR SMOLYANINOV

Simple dimensional analysis of typical nonlinear optical phenomena in metal nanoparticles indicates that qualitatively new effects may be expected in nonlinear optics of surface plasmon polaritons. It appears that some of these effects are similar to well-known effects of quantum gravitational theory.


2020 ◽  
Vol 35 (25) ◽  
pp. 2050149
Author(s):  
Shweta ◽  
Ambuj Kumar Mishra ◽  
Umesh Kumar Sharma

The concept of traversable wormhole, a hypothetical tunnel-like structure is initially proposed by Morris and Thorne (Am. J. Phys. 56, 395 (1988)) by using Einstein’s general relativity theory. Harko et al. (Phys. Rev. D 84, 024020 (2011)) defined [Formula: see text] gravity as an extended gravitational theory having terms [Formula: see text] and [Formula: see text] as Ricci scalar and trace of energy momentum respectively. In this article, we explore wormhole models for the framework of [Formula: see text] gravity by using two different shape functions. The first shape function is [Formula: see text], [Formula: see text] (proposed by Mishra and Sharma, arXiv:2003.00298v1 , 2020) and second is a hyperbolic shape function which is of the form [Formula: see text]. Geometrical behavior of wormholes are discussed in anisotropic scenario by using equation of state [Formula: see text]. The stability of models are analyzed by using equilibrium condition and determining gravitational force, anisotropic force, hydrostatic force and force due to modified gravity. For the validation of null energy condition and weak energy condition, significant role of shape function is illustrated for the presence of nonexotic matter.


2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Giuseppe Gaetano Luciano

AbstractIt has been argued that non-Gaussian statistics provide a natural framework to investigate semiclassical effects in the context of Planck-scale deformations of the Heisenberg uncertainty relation. Here we substantiate this point by considering the Unruh effect as a specific playground. By working in the realm of quantum field theory, we reformulate the derivation of the modified Unruh effect from the generalized uncertainty principle (GUP) in the language of the nonextensive Tsallis thermostatistics. We find a nontrivial monotonic relation between the nonextensivity index q and the GUP deformation parameter $$\beta $$ β , which generalizes an earlier result obtained in quantum mechanics. We then extend our analysis to black hole thermodynamics. We preliminarily discuss our outcome in the broader context of an effective description of Planck-scale gravitational physics based on Tsallis theory.


2020 ◽  
Author(s):  
Vitaly Kuyukov

In this paper, we analyze the singularity of a black hole based on a modification of general relativity. There is an equilibrium condition on the Planck scale. This makes it possible to study the thermodynamics of the singularity of a black hole.


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