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 Quasi-cosmological traversable wormholes in f(R) gravity

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Hanif Golchin ◽  
Mohammad Reza Mehdizadeh
Keyword(s):  
Energy Condition ◽  
Null Energy Condition ◽  
Einstein Gravity ◽  
Gravity Models ◽  
Energy Conditions ◽  
Asymptotically Flat ◽  
Traversable Wormholes ◽  
Whole Space ◽  
Frw Metric ◽  
Standard Energy

Abstract In this paper, we study traversable wormholes in the context of f(R) gravity. Exact solutions of traversable wormholes are found by imposing the nonconstant Ricci scalar. These solutions asymptotically match spherical, flat and hyperbolic FRW metric. By choosing some static f(R) gravity models, we verify the standard energy conditions for the asymptotically spherical, flat and hyperbolic wormhole solutions. Unlike the Einstein gravity, we find that in the context of f(R) modified gravity, the asymptotically spherical, flat and hyperbolic wormhole solutions can respect the null energy condition (NEC) at the wormhole throat and near that. We find that in some static f(R) models, asymptotically flat and hyperbolic wormholes respect the weak energy condition (WEC) through the whole space.

scholarly journals Traversable wormholes with exponential shape function in modified gravity and general relativity: A comparative study

2020 ◽  
Vol 29 (09) ◽  
pp. 2050068 ◽  
Author(s):  
Gauranga C. Samanta ◽  
Nisha Godani ◽  
Kazuharu Bamba
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Comparative Study ◽  
Modified Gravity ◽  
Shape Function ◽  
Anisotropy Parameter ◽  
Energy Conditions ◽  
Traversable Wormholes

We have proposed a novel shape function on which the metric that models traversable wormholes is dependent. Using this shape function, the energy conditions, equation-of-state and anisotropy parameter are analyzed in [Formula: see text] gravity, [Formula: see text] gravity and general relativity. Furthermore, the consequences obtained with respect to these theories are compared. In addition, the existence of wormhole geometries is investigated.

scholarly journals CROSSING THE PHANTOM DIVIDE WITH k-ESSENCE IN BRANEWORLDS

2010 ◽  
Vol 25 (29) ◽  
pp. 2469-2481 ◽  
Author(s):  
LUIS P. CHIMENTO ◽  
MÓNICA FORTE ◽  
MARTÍN G. RICHARTE
Keyword(s):  
Equation Of State ◽  
High Energy ◽  
Chaplygin Gas ◽  
Energy Conditions ◽  
De Sitter ◽  
Effective Equation ◽  
Phantom Divide ◽  
Energy Regime ◽  
High Energy Regime ◽  
Stable Stage

We study a flat three-brane in the presence of a linear k field with nonzero cosmological constant Λ4. In this model the crossing of the phantom divide (PD) occurs when the k-essence energy density becomes negative. We show that in the high energy regime the effective equation of state has a resemblance of a modified Chaplygin gas while in the low energy regime it becomes linear. We find a scale factor that begins from a singularity and evolves to a de Sitter stable stage while other solutions have a super-accelerated regime and end with a big rip. We use the energy conditions to show when the effective equation of state of the brane-universe crosses the PD.

scholarly journals Traversable wormholes in the bulge of Milky Way galaxy with Global Monopole Charge

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Susmita Sarkar ◽  
Nayan Sarkar ◽  
Farook Rahaman
Keyword(s):  
Milky Way ◽  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Radial Coordinate ◽  
Global Monopole ◽  
Milky Way Galaxy ◽  
Asymptotically Flat ◽  
Traversable Wormholes ◽  
Crucial Effect

AbstractThe present work looks for the existence of completely new wormhole geometries in the bulge of the Milky Way galaxy (MWG) situated on the dark matter (DM) density profile followed from MacMillan (MNRAS 76:465, 2017) and Boshkayev and Malafarina (MNRAS 484:3325, 2019) concerned with Global Monopole Charge. The obtained shape function is positively increasing against the radial coordinate and it increases faster with the increasing values of Global Monopole Charge. Moreover, the reported shape function satisfies all the essential criterions and hence it constructs wormhole geometry in the bulge of the MWG. Further, the DM candidate around bulge is suitable to harbor wormhole by violating the null energy condition(NEC) corresponding to three different redshift functions. The striking point of our solution is that for zero Global Monopole Charge the wormholes are asymptotically flat corresponding to the first two choices of redshift functions while for positive values of Global Monopole Charge wormhole becomes non asymptotically flat and Global Monopole Charge also has the crucial effect on the violation of NEC. In our solutions, one can note that the total amount of averaged NEC violating matter in the wormhole spacetime depends on the Global Monopole Charge $$\eta $$ η . Furthermore, the respective wormhole solutions are in equilibrium positions.

scholarly journals Traversable wormholes supported by GUP corrected Casimir energy

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Kimet Jusufi ◽  
Phongpichit Channuie ◽  
Mubasher Jamil
Keyword(s):  
Deflection Angle ◽  
Equations Of State ◽  
Generalized Uncertainty Principle ◽  
Casimir Energy ◽  
Energy Conditions ◽  
Strong Condition ◽  
Asymptotically Flat ◽  
Wormhole Throat ◽  
Classical Energy ◽  
Traversable Wormholes

Abstract In this paper, we investigate the effect of the Generalized Uncertainty Principle (GUP) in the Casimir wormhole spacetime recently proposed by Garattini (Eur Phys J C 79: 951, 2019). In particular, we consider three types of GUP relations, firstly the Kempf, Mangano and Mann (KMM) model, secondly the Detournay, Gabriel and Spindel (DGS) model, and finally the so-called type II model for the GUP principle. To this end, we consider three specific models of the redshift function along with two different equations of state (EoS), given by $${\mathcal {P}}_r(r)=\omega _r(r) \rho (r)$$Pr(r)=ωr(r)ρ(r) and $${\mathcal {P}}_t(r)=\omega _t (r){\mathcal {P}}_r(r)$$Pt(r)=ωt(r)Pr(r) and obtain a class of asymptotically flat wormhole solutions supported by Casimir energy under the effect of GUP. Furthermore we check the null, weak, and strong condition at the wormhole throat with a radius $$r_0$$r0, and we show that in general the classical energy conditions are violated by some arbitrary quantity at the wormhole throat. Importantly, we examine the wormhole geometry with semiclassical corrections via embedding diagrams. We also consider the ADM mass of the wormhole, the volume-integral quantifier to calculate the amount of the exotic matter near the wormhole throat, and the deflection angle of light.

scholarly journals Dark Matter Candidates with Dark Energy Interiors Determined by Energy Conditions

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 662 ◽  
Author(s):  
Irina Dymnikova
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Condition ◽  
Phantom Energy ◽  
Weak Energy Condition ◽  
Energy Conditions ◽  
De Sitter ◽  
Dynamical Equations ◽  
De Sitter Vacuum ◽  
Observational Signature

We outline the basic properties of regular black holes, their remnants and self-gravitating solitons G-lumps with the de Sitter and phantom interiors, which can be considered as heavy dark matter (DM) candidates generically related to a dark energy (DE). They are specified by the condition T t t = T r r and described by regular solutions of the Kerr-Shild class. Solutions for spinning objects can be obtained from spherical solutions by the Newman-Janis algorithm. Basic feature of all spinning objects is the existence of the equatorial de Sitter vacuum disk in their deep interiors. Energy conditions distinguish two types of their interiors, preserving or violating the weak energy condition dependently on violation or satisfaction of the energy dominance condition for original spherical solutions. For the 2-nd type the weak energy condition is violated and the interior contains the phantom energy confined by an additional de Sitter vacuum surface. For spinning solitons G-lumps a phantom energy is not screened by horizons and influences their observational signatures, providing a source of information about the scale and properties of a phantom energy. Regular BH remnants and G-lumps can form graviatoms binding electrically charged particles. Their observational signature is the electromagnetic radiation with the frequencies depending on the energy scale of the interior de Sitter vacuum within the range available for observations. A nontrivial observational signature of all DM candidates with de Sitter interiors predicted by analysis of dynamical equations is the induced proton decay in an underground detector like IceCUBE, due to non-conservation of baryon and lepton numbers in their GUT scale false vacuum interiors.

scholarly journals Traversable asymptotically flat wormholes in Rastall gravity

2017 ◽  
Vol 95 (12) ◽  
pp. 1257-1266 ◽  
Author(s):  
H. Moradpour ◽  
N. Sadeghnezhad ◽  
S.H. Hendi
Keyword(s):  
Energy Condition ◽  
State Parameter ◽  
Momentum Conservation ◽  
Baryonic Matter ◽  
Curved Space ◽  
Asymptotically Flat ◽  
Traversable Wormholes ◽  
Gravitational Theories ◽  
Matter Fields ◽  
Energy Momentum Conservation

There are some gravitational theories in which the ordinary energy–momentum conservation law is not valid in the curved space–time. Rastall gravity is one of the known theories in this regard, which includes a non-minimal coupling between geometry and matter fields. Equipped with the basis of such theory, we study the properties of traversable wormholes with flat asymptotes. We investigate the possibility of exact solutions by a source with the baryonic matter state parameter. Our survey indicates that Rastall theory has considerable effects on the wormhole characteristics. In addition, we study various case studies and show that the weak energy condition may be met for some solutions. We also give a discussion regarding traversibility of such wormhole geometry with phantom sources.

scholarly journals Wormhole geometries in fourth-order conformal Weyl gravity

2016 ◽  
Vol 25 (06) ◽  
pp. 1650064 ◽  
Author(s):  
Gabriele U. Varieschi ◽  
Kellie L. Ault
Keyword(s):  
General Relativity ◽  
Fourth Order ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Conformal Gravity ◽  
Flat Spacetime ◽  
Traversable Wormholes ◽  
Weyl Gravity ◽  
The Subject

We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remains the same as in the seminal study by Morris and Thorne, namely, that effective super-luminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at the junction between our solutions and flat spacetime, but we demonstrate that the averaged null energy condition (as evaluated along radial null geodesics) is satisfied for a particular set of wormhole geometries. Therefore, if fourth-order conformal Weyl gravity is a correct extension of general relativity, traversable wormholes might become a realistic solution for interstellar travel.

scholarly journals Embedding with Vaidya geometry

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
A. V. Nikolaev ◽  
S. D. Maharaj
Keyword(s):  
Equation Of State ◽  
Euclidean Space ◽  
Mass Function ◽  
Energy Conditions ◽  
Dimensional Euclidean Space ◽  
De Sitter ◽  
Radiating Star ◽  
Theory Of Gravity ◽  
Null String ◽  
Vaidya Metric

Abstract The Vaidya metric is important in describing the exterior spacetime of a radiating star and for describing astrophysical processes. In this paper we study embedding properties of the generalized Vaidya metric. We had obtained embedding conditions, for embedding into 5-dimensional Euclidean space, by two different methods and solved them in general. As a result we found the form of the mass function which generates a subclass of the generalized Vaidya metric. Our result is purely geometrical and may be applied to any theory of gravity. When we apply Einstein’s equations we find that the embedding generates an equation of state relating the null string density to the null string pressure. The energy conditions lead to particular metrics including the anti/de Sitter spacetimes.

scholarly journals Ellis wormholes in anti-de Sitter space

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Jose Luis Blázquez-Salcedo ◽  
Xiao Yan Chew ◽  
Jutta Kunz ◽  
Dong-han Yeom
Keyword(s):  
De Sitter Space ◽  
Radial Mode ◽  
Radial Coordinate ◽  
De Sitter ◽  
Asymptotically Flat ◽  
Phantom Field ◽  
Traversable Wormholes

AbstractWe construct traversable wormholes with anti-de Sitter asymptotics supported by a phantom field. These wormholes are massless and symmetric with respect to reflection of the radial coordinate $$\eta \rightarrow - \eta $$ η → - η . Their circumferential radius decreases monotonically from radial infinity to their single throat. Analogous to their asymptotically flat counterparts, these anti-de Sitter wormholes possess an unstable radial mode.

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