scholarly journals Regular braneworlds with nonlinear bulk-fluids

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Ignatios Antoniadis ◽  
Spiros Cotsakis ◽  
Ifigeneia Klaoudatou
Keyword(s):  
Equation Of State ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Matter Content ◽  
Brane World ◽  
Planck Mass ◽  
Non Linear ◽  
Finite Distance

AbstractWe construct a regular five-dimensional brane-world with localised gravity on a flat 3-brane. The matter content in the bulk is parametrised by an analog of a non-linear fluid with equation of state $$p=\gamma \rho ^\lambda $$ p = γ ρ λ between the ‘pressure’ p and the ‘density’ $$\rho $$ ρ dependent on the 5th dimension. For $$\gamma $$ γ negative and $$\lambda >1$$ λ > 1 , the null energy condition is satisfied and the geometry is free of singularities within finite distance from the brane, while the induced four-dimensional Planck mass is finite.

scholarly journals NON-SINGULAR BLACK-HOLES ON THE BRANE

2004 ◽  
Vol 13 (06) ◽  
pp. 1095-1103 ◽  
Author(s):  
S. SHANKARANARAYANAN ◽  
NARESH DADHICH
Keyword(s):  
Energy Condition ◽  
Null Energy Condition ◽  
Effective Field ◽  
Brane World ◽  
Spherically Symmetric ◽  
Null Condition ◽  
Field Equations ◽  
World Model ◽  
Weyl Curvature ◽  
Black Hole Solutions

We investigate the possibility of obtaining non-singular black-hole solutions in the brane world model by solving the effective field equations for the induced metric on the brane. The Reissner–Nordstrom solution on the brane was obtained by Dadhich et al. by imposing the null energy condition on the 3-brane for a bulk having non-zero Weyl curvature. In this work, we relax the condition of vanishing scalar curvature R, however, retaining the null condition. We have shown that it is possible to obtain a class of static non-singular spherically symmetric brane space–times which admits horizon. We obtain one such class of solution which is a regular version of the Reissner–Nordstrom solution in the standard general relativity.

scholarly journals Wormhole Models and Energy Conditions in f ℛ Gravity with the Hu–Sawicki Model

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ouziala Ikram ◽  
G. Mustafa
Keyword(s):  
Equation Of State ◽  
Symmetric Space ◽  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Space Time ◽  
Energy Conditions ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Nature Of Matter

In this recent study, we shall investigate the wormhole models with a Hu–Sawicki model in the framework of f ℛ gravity. Spherically static symmetric space-time is considered to construct wormhole models with the anisotropic fluid distribution. The traceless matter is discussed by imposing a particular equation of state. To address the important conditions of the shape function of the wormhole geometry, we have used the particular values of the involved parameters. Furthermore, different energy conditions are discussed to check the nature of matter against two specific models. The null energy condition is observed to be violated for both of the models. It is mentioned that our inquired results are acceptable.

scholarly journals Phantom-Like Behavior in Modified Teleparallel Gravity

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Sakineh Karimzadeh ◽  
Raheleh Shojaee
Keyword(s):  
Equation Of State ◽  
Parameter Space ◽  
Energy Condition ◽  
State Parameter ◽  
Teleparallel Gravity ◽  
Null Energy Condition ◽  
Phantom Field ◽  
Equation Of State Parameter ◽  
The Universe

The recent data from Planck2018 shows that the equation of state parameter of effective cosmic fluid today is w0=-1.03±0.03. This indicates that it is possible for the universe to be in a phantom dominated era today. While a phantom field is essentially capable of explaining this observation, it suffers from some serious problems such as instabilities and violation of the null energy condition. So, it would be interesting to realize this effective phantom behavior without adopting a phantom field. In this paper, we study possible realization of an effective phantom behavior in modified teleparallel gravity. We show that modified teleparallel gravity is able essentially to realize an effective phantom-like behavior in the absence of a phantom field. For this purpose, we choose some observationally viable f(T) functions and prove that there are some subspaces of the models parameter space capable of realizing a phantom-like behavior without adopting a phantom field.

scholarly journals On the Nature of Exotic Matter in Morris-Thorne Wormholes

2020 ◽  
Vol 4 (3) ◽  
Author(s):  
Peter K F Kuhfittig ◽  
Keyword(s):  
Equation Of State ◽  
Shape Function ◽  
Energy Condition ◽  
Radial Pressure ◽  
Phantom Energy ◽  
Null Energy Condition ◽  
Exotic Matter ◽  
Typical Shape

It is well known that phantom energy, which is characterized by the equation of state p = ωρ, ω < −1, can support Morris-Thorne wormholes since it leads to a violation of the null energy condition. The purpose of this note is to show that the converse is also true in the following sense: for a typical shape function, the equation of state of exotic matter in the vicinity of the throat is given by p↓r = ωρ, ω < −1, where pr is the radial pressure.

scholarly journals ANEC in λϕ4 theory

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Teresa Bautista ◽  
Lorenzo Casarin ◽  
Hadi Godazgar
Keyword(s):  
Critical Points ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Renormalisation Group ◽  
Quartic Coupling ◽  
Third Order ◽  
Expectation Value ◽  
Scalar State

Abstract Motivated by the goal of applying the average null energy condition (ANEC) to renormalisation group flows, we calculate in λϕ4 theory the expectation value of the ANEC operator in a particular scalar state perturbatively up to third order in the quartic coupling and verify the expected CFT answer. The work provides the technical tools for studying the expectation value of the ANEC operator in more interesting states, for example tensorial states relevant to the Hofman-Maldacena collider bounds, away from critical points.

scholarly journals Traversable wormholes in Einsteinian cubic gravity

2019 ◽  
Vol 35 (06) ◽  
pp. 2050017 ◽  
Author(s):  
Mohammad Reza Mehdizadeh ◽  
Amir Hadi Ziaie
Keyword(s):  
Equation Of State ◽  
Gravitational Lensing ◽  
Energy Condition ◽  
Higher Order ◽  
Energy Conditions ◽  
Geodesic Motion ◽  
De Sitter ◽  
Asymptotically Flat ◽  
Traversable Wormholes ◽  
Standard Energy

In this work, we investigate wormhole configurations described by a constant redshift function in Einstein-Cubic gravity ( ECG ). We derive analytical wormhole geometries by assuming a particular equation of state ( EoS ) and investigate the possibility that these solutions satisfy the standard energy conditions. We introduce exact asymptotically flat and anti-de Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are obtained by imposing suitable values for the parameters of the theory so that the resulted geometries satisfy the weak energy condition ( WEC ) in the vicinity of the throat, due to the presence of higher-order curvature terms. Moreover, we find that AdS solutions satisfy the WEC throughout the spacetime. A description of the geodesic motion of time-like and null particles is presented for the obtained wormhole solutions. Also, using gravitational lensing effects, observational features of the wormhole structure are discussed.

scholarly journals Singularity Theorems in the Effective Field Theory for Quantum Gravity at Second Order in Curvature

Universe ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. 171
Author(s):  
Folkert Kuipers ◽  
Xavier Calmet
Keyword(s):  
Field Theory ◽  
Quantum Gravity ◽  
Effective Field Theory ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Effective Field ◽  
Second Order ◽  
Jordan Frame ◽  
Singularity Theorems ◽  
Massive Spin

In this paper, we discuss singularity theorems in quantum gravity using effective field theory methods. To second order in curvature, the effective field theory contains two new degrees of freedom which have important implications for the derivation of these theorems: a massive spin-2 field and a massive spin-0 field. Using an explicit mapping of this theory from the Jordan frame to the Einstein frame, we show that the massive spin-2 field violates the null energy condition, while the massive spin-0 field satisfies the null energy condition, but may violate the strong energy condition. Due to this violation, classical singularity theorems are no longer applicable, indicating that singularities can be avoided, if the leading quantum corrections are taken into account.

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