In this article, our primary objective is to construct new wormhole solutions by involving a Yukawa-corrected form of Casimir energy density in a well-motivated gravitational theory that allows the coupling of curvatu...In this article, our primary objective is to construct new wormhole solutions by involving a Yukawa-corrected form of Casimir energy density in a well-motivated gravitational theory that allows the coupling of curvature and matter, namely the F(R,T) theory. To achieve this goal, a wormhole geometry exhibiting a spherically-symmetric nature is taken into account and anisotropic fluid is assumed to be the background ordinary matter source.We first consider the simple linear F(R,T) theory by assuming F(R,T) = R+ 2ζ T with L_m=-P(average pressure). Secondly, we utilize the conformal symmetries of the spherical-symmetric geometry for simplifying the resulting field equations and obtain the corresponding analytical form of the wormhole solution. In both cases, the viability of the proposed solutions is examined by checking the basic features of the wormhole shape model along with the validity of null energy constraints. Further, we study the volume integral quantifier(VIQ), exoticity factor and stability through the Tolman–Oppenheimer–Volkov(TOV) equation as well as the adiabatic index, active gravitational mass and complexity factor graphically. Lastly, we use a newly-proposed wormhole shape function to find the expressions of state variables and discuss the validity of energy bounds. We also explore the significance of this wormhole shape model through different quantities graphically. In all scenarios, the presented solutions are found to be new, promising and viable.展开更多
This work revisits the analysis of charged Casimir wormhole solutions within the framework of Einstein–Gauss–Bonnet(EGB)gravity,addressing a critical inconsistency in the approach presented by Farooq et al.Specifica...This work revisits the analysis of charged Casimir wormhole solutions within the framework of Einstein–Gauss–Bonnet(EGB)gravity,addressing a critical inconsistency in the approach presented by Farooq et al.Specifically,we show that their use of four-dimensional Casimir and electric field energy densities are incompatible with the higher-dimensional nature of EGB gravity,which requires D≥5.We provide the correct formulation for the energy densities and revise the wormhole properties under this framework,offering a refined perspective on the interplay between extra dimensions and Casimir effects in EGB gravity.展开更多
While wormholes are just as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. To allow for the possibility of interstellar travel, a macroscopic...While wormholes are just as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. To allow for the possibility of interstellar travel, a macroscopic wormhole would need to maintain sufficiently low radial tidal forces. It is proposed in this paper that the assumption of zero tidal forces, i.e., the limiting case, is sufficient for overcoming the restrictions from quantum field theory. The feasibility of this approach is subsequently discussed by 1) introducing the additional conditions needed to ensure that the radial tidal forces can indeed be sufficiently low and 2) by viewing traversable wormholes as emergent phenomena, thereby increasing the likelihood of their existence.展开更多
This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while ...This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while the surface pressure is negative, resulting in , thereby signaling a violation of the null energy condition, a necessary condition for holding a wormhole open. For a Morris-Thorne wormhole, matter that violates the null energy condition is referred to as “exotic”. For the thin-shell wormholes in this paper, however, the violation has a physical explanation since it is a direct consequence of the embedding theory in conjunction with the assumption of conformal symmetry. These properties avoid the need to hypothesize the existence of the highly problematical exotic matter.展开更多
While wormholes are as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. In particular, holding a wormhole open requires a violation of the null...While wormholes are as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. In particular, holding a wormhole open requires a violation of the null energy condition, calling for the existence of exotic matter. The Casimir effect has shown that this physical requirement can be met on a small scale, thereby solving a key conceptual problem. The Casimir effect does not, however, guarantee that the small-scale violation is sufficient for supporting a macroscopic wormhole. The purpose of this paper is to connect the Casimir effect to noncommutative geometry, which also aims to accommodate small-scale effects, the difference being that these can now be viewed as intrinsic properties of spacetime. As a result, the noncommutative effects can be implemented by modifying only the energy momentum tensor in the Einstein field equations, while leaving the Einstein tensor unchanged. The wormhole can therefore be macroscopic in spite of the small Casimir effect.展开更多
This paper discusses the effect that conformal symmetry can have on a charged wormhole. The analysis yields a physical interpretation of the conformal factor in terms of the electric charge. The rate of change of the ...This paper discusses the effect that conformal symmetry can have on a charged wormhole. The analysis yields a physical interpretation of the conformal factor in terms of the electric charge. The rate of change of the conformal factor determines much of the outcome, which ranges from having no solution to wormholes having either one or two throats.展开更多
In this paper,we analyze thin-shell wormholes from two identical copies of charged static cylindrically symmetric spacetimes using Visser’s‘cut and paste’approach under the influence of f(R,T)gravity Harko,Lobo,Noj...In this paper,we analyze thin-shell wormholes from two identical copies of charged static cylindrically symmetric spacetimes using Visser’s‘cut and paste’approach under the influence of f(R,T)gravity Harko,Lobo,Nojiri,and Odintsov(2011,Phys.Rev.D 84,024020).In this scenario,the modified Chaplygin gas supports the exotic matter in the shell which allows,one to examine the dynamics of constructed wormholes.We utilize the junction condition to connect the interior and exterior geometries across the hypersurface and calculate different components of the Lanczos equation recently computed by Roza in Rosa(2021,Phy.Rev.D 103,104069).We analyze the stability of the thin-shell wormhole models under linear perturbations while keeping the cylindrical symmetry and also examine the influence of charge on their stability.The positive quantity of the second derivative of potential at the throat radius might be interpreted as the stability criterion.We find both unstable and stable wormhole solutions for different parameters included in the equation of state and specific forms of considered gravity and illustrate them theoretically as well as graphically.We examine the impact of electric charge on the stability region of a constructed wormhole,which suggests that a wormhole model with a charge may exhibit more stable behavior compared to an uncharged system.展开更多
When Morris and Thorne first proposed that wormholes might be actual physical structures suitable for interstellar travel, they needed to pay close attention to certain traversability conditions such as low tidal forc...When Morris and Thorne first proposed that wormholes might be actual physical structures suitable for interstellar travel, they needed to pay close attention to certain traversability conditions such as low tidal forces, which placed severe constraints on the wormhole geometry. Even more problematical was the need for “exotic matter” resulting from the unavoidable violation of the null energy condition required to hold a wormhole open. The purpose of this paper is to overcome these problems by starting with the charged wormhole model of Kim and Lee and assuming a noncommutative-geometry background: the violation of the null energy condition can be attributed to the latter, while the electric charge allows the reduction of the tidal forces to acceptable levels without invoking the trivial zero-tidal-force assumption.展开更多
In the context of modified gravity theory, we study time-dependent wormhole spacetimes in the radiation background. In this framework, we attempt to generalize the thermodynamic properties of time-dependent wormholes ...In the context of modified gravity theory, we study time-dependent wormhole spacetimes in the radiation background. In this framework, we attempt to generalize the thermodynamic properties of time-dependent wormholes in gravity. Finally, at event horizon, the rate of change of total entropy has been discussed.展开更多
It is shown in the first part of this paper that a combined model comprising ordinary and quintessential matter can support a traversable wormhole in Einstein-Maxwell gravity. Since the solution allows zero tidal forc...It is shown in the first part of this paper that a combined model comprising ordinary and quintessential matter can support a traversable wormhole in Einstein-Maxwell gravity. Since the solution allows zero tidal forces, the wormhole is suitable for a humanoid traveler. The second part of the paper shows that the electric field can be eliminated (Einstein gravity), but only by tolerating enormous tidal forces. Such a wormhole would still be capable of transmitting signals.展开更多
The Brouwer fixed-point theorem in topology states that for any continuous mapping <em>f</em> on a compact convex set into itself admits a fixed point, <em>i.e.</em>, a point <em>x</em...The Brouwer fixed-point theorem in topology states that for any continuous mapping <em>f</em> on a compact convex set into itself admits a fixed point, <em>i.e.</em>, a point <em>x</em><sub>0</sub> such that<em> f</em>(<em>x</em><sub>0</sub>) = <em>x</em><sub>0</sub>. Under suitable conditions, this fixed point corresponds to the throat of a traversable wormhole, <em>i.e.</em>, <em>b</em>(<em>r</em><sub>0</sub>) = <em>r</em><sub>0</sub> for the shape function <em>b</em> = <em>b</em>(<em>r</em>). The possible existence of wormholes can therefore be deduced from purely mathematical considerations without going beyond the existing physical requirements.展开更多
The Schwarzschild solution to the Einstein field equation leads to a solution that has been interpreted as wormholes. While many researchers have been sceptical about this interpretation, others have been positive abo...The Schwarzschild solution to the Einstein field equation leads to a solution that has been interpreted as wormholes. While many researchers have been sceptical about this interpretation, others have been positive about it. We show that wormholes are not mathematically allowed in the spherical metric of a newly-released unified quantum gravity theory known as collision space-time [1] [2] [3]. We, therefore, have reasons to believe that wormholes in general relativity theory are nothing more than a mathematical artefact due to an incomplete theory, but we are naturally open to discussions about this point. The premise that wormholes likely do not exist falls nicely into line with a series of other intuitive predictions from collision space-time where general relativity theory falls short, such as matching the full spectrum of the Planck scale for micro “black holes”.展开更多
The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To ...The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To begin with, the extra spatial dimension is assumed to be time dependent, while the redshift and shape functions, as well as the extra dimension, are functions of both r and l, the respective radial and extra coordinates;the last of these is therefore a function of r, l, and t. The main objective is to determine the conditions that allow the throat of the wormhole to be threaded with ordinary matter (by respecting the null energy condition) and that the same conditions lead to a violation of the null energy condition in the fifth dimension, which is therefore responsible for sustaining the wormhole. The dependence of the extra dimension on l and t is subject to additional conditions that are subsequently analyzed in this paper. Finally, the extra dimension may be extremely small or even curled up.展开更多
Dark energy is typically the principal component needed for the traversability of wormholes(WH),as it provides the negative gravity effect required to keep the throat open.However,can this be achieved without dark ene...Dark energy is typically the principal component needed for the traversability of wormholes(WH),as it provides the negative gravity effect required to keep the throat open.However,can this be achieved without dark energy?It turns out that if we couple the trace of energy-momentum with the standard Einstein-Hilbert Lagrangian and utilize a specific equation of state(EoS),dark energy may be obviated.The Casimir stress energy is known to result in the violation of the null energy condition(NEC)on the energy momentum tensor.This phenomenon makes such an EoS an ideal candidate for generating traversable WH geometries.The laboratory proven phenomenon provides a natural mechanism to sustain an open WH throat without relying on dark energy.Therefore,we generate two classes of WH solutions using this in energy-momentum trace-coupling gravity.For the specific choice of the Casimir EoS relating the energy-momentum tensor components[Kar and Sahdev:Phys.Rev.D 52,2030(1995)]and different choices of redshift functions,we determine the WH geometry completely.The obtained WH solutions violate the NECs,and all qualitative constraints demanded for physically realizable WHs are satisfied.This is demonstrated via graphical plots for a suitably chosen range of coupling parameter values.Furthermore,our study investigates the repulsive effect of gravity,revealing that its presence leads to a negative deflection angle for photons traveling along null geodesics.Notably,we observe a consistent pattern of negative values for the deflection angle across all values of r_(0) in the three scenarios considered,thus indicating the clear manifestation of the repulsive gravity effect.All of this is possible without invoking the existence of dark energy.展开更多
In spite of their speculative nature,traversable wormholes are a topic of interest that started with the Einstein-Rosen bridge in 1935 and became a major research area with the introduction of the Morris-Thorne wormho...In spite of their speculative nature,traversable wormholes are a topic of interest that started with the Einstein-Rosen bridge in 1935 and became a major research area with the introduction of the Morris-Thorne wormhole in 1988.It also became apparent in time that such wormholes are likely to be compact stellar objects,akin to neutron stars.Although widely discussed,wormholes having a low energy density may therefore not be massive enough to exist on a macroscopic scale.Important examples are wormholes based on a noncommutative geometry background and wormholes supported by the negative energy density sourced by the Casimir effect.The main goal of this paper is to invoke f(Q)modified gravity to provide the extra degrees of freedom to help overcome these obstacles.展开更多
In this work,using the thin disk model,we examine the optical observations of asymmetric thin-shell wormholes(ATWs)within the theoretical framework of higher-order non-commutative geometry.By utilizing ray tracing tec...In this work,using the thin disk model,we examine the optical observations of asymmetric thin-shell wormholes(ATWs)within the theoretical framework of higher-order non-commutative geometry.By utilizing ray tracing technology,the trajectories of photons under various relevant parameters,as well as the optical observational appearance of ATW,can be accurately simulated.Compared to the black hole(BH)spacetime,observational images of ATW will exhibit extra bright ring structures.The results show that an increase in the non-commutative parameter leads to the innermost extra photon ring moving away from the shadow region,while the second extra photon ring moves closer to the shadow region.However,only one extra bright ring structure is observed in the image when the non-commutative parameter increases toθ=0.03,implying that the observed features of ATWs seem to become increasingly visually similar to a BH with increasingθ.Furthermore,an increase in the mass ratio will result in a reduction of the radius of the innermost extra photon ring,whereas an increase in the throat radius will lead to an expansion of its radius.Notably,neither parameter has a significant impact on the size of the second extra photon ring.These findings significantly advance our theoretical understanding of the optical features of ATWs with higher-order non-commutative corrections.展开更多
This investigation assesses the feasibility of a traversable wormhole by examining the energy densities associated with charged Casimir phenomena.We focus on the influence of the electromagnetic field created by an el...This investigation assesses the feasibility of a traversable wormhole by examining the energy densities associated with charged Casimir phenomena.We focus on the influence of the electromagnetic field created by an electric charge as well as the negative energy density arising from the Casimir source.We have developed different shape functions by defining energy densities from this combination.This paper explores various configurations of Casimir energy densities,specifically those occurring between parallel plates,cylinders and spheres positioned at specified distances from each other.Furthermore,the impact of the generalized uncertainty principle correction is also examined.The behavior of wormhole conditions is evaluated based on the Gauss–Bonnet coupled parameter(μ)and electric charge(Q)through the electromagnetic energy density constraint.This is attributed to the fact that the electromagnetic field satisfies the characteristicρ=-pr.Subsequently,we examine the active gravitational mass of the generated wormhole geometries and explore the behavior ofμand Q concerning active mass.The embedding representations for all formulated shape functions are examined.Investigations of the complexity factor of the charged Casimir wormhole have demonstrated that the values of the complexity factor consistently fall within a particular range in all scenarios.Finally,using the generalized Tolman–Oppenheimer–Volkoff equation,we examine the stability of the resulting charged Casimir wormhole solutions.展开更多
This study investigates the observational signatures of traversable Simpson-Visser wormholes illuminated by luminous celestial spheres and orbiting hot spots.We demonstrate that when light sources and observers are on...This study investigates the observational signatures of traversable Simpson-Visser wormholes illuminated by luminous celestial spheres and orbiting hot spots.We demonstrate that when light sources and observers are on the same side of a wormhole,the images of the wormhole mimic those of a black hole.However,when the light source is positioned opposite the observer,photons traversing the wormhole throat generate distinct observational signatures.Specifically,unlike black hole images,wormhole images are confined in a critical curve,resulting in smaller centroid variations.Furthermore,the light curve of hot spots can exhibit additional peaks.展开更多
A traversable wormhole generally violates the averaged null energy condition, typically requiring exotic matter. Recently, it was discovered that a traversable wormhole can be realized with non-exotic matter in Einste...A traversable wormhole generally violates the averaged null energy condition, typically requiring exotic matter. Recently, it was discovered that a traversable wormhole can be realized with non-exotic matter in EinsteinDirac-Maxwell theories in flat space. This study extends the discussion to AdS spacetime and finds traversable wormholes with spherical and planar topologies. Furthermore, based on the AdS/CFT correspondence, we compute the entanglement entropy of strips and disks on the two AdS boundaries of the wormhole. We find that the entanglement entropy undergoes a phase transition as the subsystem size increases.展开更多
Wormholes of complex scalar fields with spontaneous breaking symmetry at finite temperature are discussed. It has been found out that the temperature effect of Coleman-Lee wormholes is important. This type of wormhole...Wormholes of complex scalar fields with spontaneous breaking symmetry at finite temperature are discussed. It has been found out that the temperature effect of Coleman-Lee wormholes is important. This type of wormholes can exist within the temperature regions 0≤T≤M_p only.展开更多
文摘In this article, our primary objective is to construct new wormhole solutions by involving a Yukawa-corrected form of Casimir energy density in a well-motivated gravitational theory that allows the coupling of curvature and matter, namely the F(R,T) theory. To achieve this goal, a wormhole geometry exhibiting a spherically-symmetric nature is taken into account and anisotropic fluid is assumed to be the background ordinary matter source.We first consider the simple linear F(R,T) theory by assuming F(R,T) = R+ 2ζ T with L_m=-P(average pressure). Secondly, we utilize the conformal symmetries of the spherical-symmetric geometry for simplifying the resulting field equations and obtain the corresponding analytical form of the wormhole solution. In both cases, the viability of the proposed solutions is examined by checking the basic features of the wormhole shape model along with the validity of null energy constraints. Further, we study the volume integral quantifier(VIQ), exoticity factor and stability through the Tolman–Oppenheimer–Volkov(TOV) equation as well as the adiabatic index, active gravitational mass and complexity factor graphically. Lastly, we use a newly-proposed wormhole shape function to find the expressions of state variables and discuss the validity of energy bounds. We also explore the significance of this wormhole shape model through different quantities graphically. In all scenarios, the presented solutions are found to be new, promising and viable.
基金the National Council for Scientific and Technological Development-CNPq(PQ 315926/2021-0)FUNCAP,through the project BP5-0197-00117.01.00/22,for financial support。
文摘This work revisits the analysis of charged Casimir wormhole solutions within the framework of Einstein–Gauss–Bonnet(EGB)gravity,addressing a critical inconsistency in the approach presented by Farooq et al.Specifically,we show that their use of four-dimensional Casimir and electric field energy densities are incompatible with the higher-dimensional nature of EGB gravity,which requires D≥5.We provide the correct formulation for the energy densities and revise the wormhole properties under this framework,offering a refined perspective on the interplay between extra dimensions and Casimir effects in EGB gravity.
文摘While wormholes are just as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. To allow for the possibility of interstellar travel, a macroscopic wormhole would need to maintain sufficiently low radial tidal forces. It is proposed in this paper that the assumption of zero tidal forces, i.e., the limiting case, is sufficient for overcoming the restrictions from quantum field theory. The feasibility of this approach is subsequently discussed by 1) introducing the additional conditions needed to ensure that the radial tidal forces can indeed be sufficiently low and 2) by viewing traversable wormholes as emergent phenomena, thereby increasing the likelihood of their existence.
文摘This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while the surface pressure is negative, resulting in , thereby signaling a violation of the null energy condition, a necessary condition for holding a wormhole open. For a Morris-Thorne wormhole, matter that violates the null energy condition is referred to as “exotic”. For the thin-shell wormholes in this paper, however, the violation has a physical explanation since it is a direct consequence of the embedding theory in conjunction with the assumption of conformal symmetry. These properties avoid the need to hypothesize the existence of the highly problematical exotic matter.
文摘While wormholes are as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. In particular, holding a wormhole open requires a violation of the null energy condition, calling for the existence of exotic matter. The Casimir effect has shown that this physical requirement can be met on a small scale, thereby solving a key conceptual problem. The Casimir effect does not, however, guarantee that the small-scale violation is sufficient for supporting a macroscopic wormhole. The purpose of this paper is to connect the Casimir effect to noncommutative geometry, which also aims to accommodate small-scale effects, the difference being that these can now be viewed as intrinsic properties of spacetime. As a result, the noncommutative effects can be implemented by modifying only the energy momentum tensor in the Einstein field equations, while leaving the Einstein tensor unchanged. The wormhole can therefore be macroscopic in spite of the small Casimir effect.
文摘This paper discusses the effect that conformal symmetry can have on a charged wormhole. The analysis yields a physical interpretation of the conformal factor in terms of the electric charge. The rate of change of the conformal factor determines much of the outcome, which ranges from having no solution to wormholes having either one or two throats.
文摘In this paper,we analyze thin-shell wormholes from two identical copies of charged static cylindrically symmetric spacetimes using Visser’s‘cut and paste’approach under the influence of f(R,T)gravity Harko,Lobo,Nojiri,and Odintsov(2011,Phys.Rev.D 84,024020).In this scenario,the modified Chaplygin gas supports the exotic matter in the shell which allows,one to examine the dynamics of constructed wormholes.We utilize the junction condition to connect the interior and exterior geometries across the hypersurface and calculate different components of the Lanczos equation recently computed by Roza in Rosa(2021,Phy.Rev.D 103,104069).We analyze the stability of the thin-shell wormhole models under linear perturbations while keeping the cylindrical symmetry and also examine the influence of charge on their stability.The positive quantity of the second derivative of potential at the throat radius might be interpreted as the stability criterion.We find both unstable and stable wormhole solutions for different parameters included in the equation of state and specific forms of considered gravity and illustrate them theoretically as well as graphically.We examine the impact of electric charge on the stability region of a constructed wormhole,which suggests that a wormhole model with a charge may exhibit more stable behavior compared to an uncharged system.
文摘When Morris and Thorne first proposed that wormholes might be actual physical structures suitable for interstellar travel, they needed to pay close attention to certain traversability conditions such as low tidal forces, which placed severe constraints on the wormhole geometry. Even more problematical was the need for “exotic matter” resulting from the unavoidable violation of the null energy condition required to hold a wormhole open. The purpose of this paper is to overcome these problems by starting with the charged wormhole model of Kim and Lee and assuming a noncommutative-geometry background: the violation of the null energy condition can be attributed to the latter, while the electric charge allows the reduction of the tidal forces to acceptable levels without invoking the trivial zero-tidal-force assumption.
文摘In the context of modified gravity theory, we study time-dependent wormhole spacetimes in the radiation background. In this framework, we attempt to generalize the thermodynamic properties of time-dependent wormholes in gravity. Finally, at event horizon, the rate of change of total entropy has been discussed.
文摘It is shown in the first part of this paper that a combined model comprising ordinary and quintessential matter can support a traversable wormhole in Einstein-Maxwell gravity. Since the solution allows zero tidal forces, the wormhole is suitable for a humanoid traveler. The second part of the paper shows that the electric field can be eliminated (Einstein gravity), but only by tolerating enormous tidal forces. Such a wormhole would still be capable of transmitting signals.
文摘The Brouwer fixed-point theorem in topology states that for any continuous mapping <em>f</em> on a compact convex set into itself admits a fixed point, <em>i.e.</em>, a point <em>x</em><sub>0</sub> such that<em> f</em>(<em>x</em><sub>0</sub>) = <em>x</em><sub>0</sub>. Under suitable conditions, this fixed point corresponds to the throat of a traversable wormhole, <em>i.e.</em>, <em>b</em>(<em>r</em><sub>0</sub>) = <em>r</em><sub>0</sub> for the shape function <em>b</em> = <em>b</em>(<em>r</em>). The possible existence of wormholes can therefore be deduced from purely mathematical considerations without going beyond the existing physical requirements.
文摘The Schwarzschild solution to the Einstein field equation leads to a solution that has been interpreted as wormholes. While many researchers have been sceptical about this interpretation, others have been positive about it. We show that wormholes are not mathematically allowed in the spherical metric of a newly-released unified quantum gravity theory known as collision space-time [1] [2] [3]. We, therefore, have reasons to believe that wormholes in general relativity theory are nothing more than a mathematical artefact due to an incomplete theory, but we are naturally open to discussions about this point. The premise that wormholes likely do not exist falls nicely into line with a series of other intuitive predictions from collision space-time where general relativity theory falls short, such as matching the full spectrum of the Planck scale for micro “black holes”.
文摘The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To begin with, the extra spatial dimension is assumed to be time dependent, while the redshift and shape functions, as well as the extra dimension, are functions of both r and l, the respective radial and extra coordinates;the last of these is therefore a function of r, l, and t. The main objective is to determine the conditions that allow the throat of the wormhole to be threaded with ordinary matter (by respecting the null energy condition) and that the same conditions lead to a violation of the null energy condition in the fifth dimension, which is therefore responsible for sustaining the wormhole. The dependence of the extra dimension on l and t is subject to additional conditions that are subsequently analyzed in this paper. Finally, the extra dimension may be extremely small or even curled up.
基金Sudan Hansraj is grateful to the National Research Foundation of South Africa for support through Grant 138012the National Research Foundation of South Africa for the award of a postdoctoral fellowship。
文摘Dark energy is typically the principal component needed for the traversability of wormholes(WH),as it provides the negative gravity effect required to keep the throat open.However,can this be achieved without dark energy?It turns out that if we couple the trace of energy-momentum with the standard Einstein-Hilbert Lagrangian and utilize a specific equation of state(EoS),dark energy may be obviated.The Casimir stress energy is known to result in the violation of the null energy condition(NEC)on the energy momentum tensor.This phenomenon makes such an EoS an ideal candidate for generating traversable WH geometries.The laboratory proven phenomenon provides a natural mechanism to sustain an open WH throat without relying on dark energy.Therefore,we generate two classes of WH solutions using this in energy-momentum trace-coupling gravity.For the specific choice of the Casimir EoS relating the energy-momentum tensor components[Kar and Sahdev:Phys.Rev.D 52,2030(1995)]and different choices of redshift functions,we determine the WH geometry completely.The obtained WH solutions violate the NECs,and all qualitative constraints demanded for physically realizable WHs are satisfied.This is demonstrated via graphical plots for a suitably chosen range of coupling parameter values.Furthermore,our study investigates the repulsive effect of gravity,revealing that its presence leads to a negative deflection angle for photons traveling along null geodesics.Notably,we observe a consistent pattern of negative values for the deflection angle across all values of r_(0) in the three scenarios considered,thus indicating the clear manifestation of the repulsive gravity effect.All of this is possible without invoking the existence of dark energy.
文摘In spite of their speculative nature,traversable wormholes are a topic of interest that started with the Einstein-Rosen bridge in 1935 and became a major research area with the introduction of the Morris-Thorne wormhole in 1988.It also became apparent in time that such wormholes are likely to be compact stellar objects,akin to neutron stars.Although widely discussed,wormholes having a low energy density may therefore not be massive enough to exist on a macroscopic scale.Important examples are wormholes based on a noncommutative geometry background and wormholes supported by the negative energy density sourced by the Casimir effect.The main goal of this paper is to invoke f(Q)modified gravity to provide the extra degrees of freedom to help overcome these obstacles.
基金supported by the National Natural Science Foundation of China(11903025)by the Sichuan Science and Technology Program(2024NSFSC1999)。
文摘In this work,using the thin disk model,we examine the optical observations of asymmetric thin-shell wormholes(ATWs)within the theoretical framework of higher-order non-commutative geometry.By utilizing ray tracing technology,the trajectories of photons under various relevant parameters,as well as the optical observational appearance of ATW,can be accurately simulated.Compared to the black hole(BH)spacetime,observational images of ATW will exhibit extra bright ring structures.The results show that an increase in the non-commutative parameter leads to the innermost extra photon ring moving away from the shadow region,while the second extra photon ring moves closer to the shadow region.However,only one extra bright ring structure is observed in the image when the non-commutative parameter increases toθ=0.03,implying that the observed features of ATWs seem to become increasingly visually similar to a BH with increasingθ.Furthermore,an increase in the mass ratio will result in a reduction of the radius of the innermost extra photon ring,whereas an increase in the throat radius will lead to an expansion of its radius.Notably,neither parameter has a significant impact on the size of the second extra photon ring.These findings significantly advance our theoretical understanding of the optical features of ATWs with higher-order non-commutative corrections.
基金the Deanship of Research and Graduate Studies at King Khalid University for funding this work through a Large Research Project under Grant No.RGP2/453/45partially supported by the National Natural Science Foundation of China under Grant No.11988101。
文摘This investigation assesses the feasibility of a traversable wormhole by examining the energy densities associated with charged Casimir phenomena.We focus on the influence of the electromagnetic field created by an electric charge as well as the negative energy density arising from the Casimir source.We have developed different shape functions by defining energy densities from this combination.This paper explores various configurations of Casimir energy densities,specifically those occurring between parallel plates,cylinders and spheres positioned at specified distances from each other.Furthermore,the impact of the generalized uncertainty principle correction is also examined.The behavior of wormhole conditions is evaluated based on the Gauss–Bonnet coupled parameter(μ)and electric charge(Q)through the electromagnetic energy density constraint.This is attributed to the fact that the electromagnetic field satisfies the characteristicρ=-pr.Subsequently,we examine the active gravitational mass of the generated wormhole geometries and explore the behavior ofμand Q concerning active mass.The embedding representations for all formulated shape functions are examined.Investigations of the complexity factor of the charged Casimir wormhole have demonstrated that the values of the complexity factor consistently fall within a particular range in all scenarios.Finally,using the generalized Tolman–Oppenheimer–Volkoff equation,we examine the stability of the resulting charged Casimir wormhole solutions.
基金Supported in part by the the National Natural Science Foundation of China(12105191,12275183,12275184,11875196)。
文摘This study investigates the observational signatures of traversable Simpson-Visser wormholes illuminated by luminous celestial spheres and orbiting hot spots.We demonstrate that when light sources and observers are on the same side of a wormhole,the images of the wormhole mimic those of a black hole.However,when the light source is positioned opposite the observer,photons traversing the wormhole throat generate distinct observational signatures.Specifically,unlike black hole images,wormhole images are confined in a critical curve,resulting in smaller centroid variations.Furthermore,the light curve of hot spots can exhibit additional peaks.
基金Supported by the National Natural Science Foundation of China (12275366)。
文摘A traversable wormhole generally violates the averaged null energy condition, typically requiring exotic matter. Recently, it was discovered that a traversable wormhole can be realized with non-exotic matter in EinsteinDirac-Maxwell theories in flat space. This study extends the discussion to AdS spacetime and finds traversable wormholes with spherical and planar topologies. Furthermore, based on the AdS/CFT correspondence, we compute the entanglement entropy of strips and disks on the two AdS boundaries of the wormhole. We find that the entanglement entropy undergoes a phase transition as the subsystem size increases.
基金Project supported by the National Natural Science Foundation of China
文摘Wormholes of complex scalar fields with spontaneous breaking symmetry at finite temperature are discussed. It has been found out that the temperature effect of Coleman-Lee wormholes is important. This type of wormholes can exist within the temperature regions 0≤T≤M_p only.
