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
The Sine and Wormhole Energy Whale Optimization Algorithm(SWEWOA)represents an advanced solution method for resolving Optimal Power Flow(OPF)problems in power systems equipped with Flexible AC Transmission System(FACT...The Sine and Wormhole Energy Whale Optimization Algorithm(SWEWOA)represents an advanced solution method for resolving Optimal Power Flow(OPF)problems in power systems equipped with Flexible AC Transmission System(FACTS)devices which include Thyristor-Controlled Series Compensator(TCSC),Thyristor-Controlled Phase Shifter(TCPS),and Static Var Compensator(SVC).SWEWOA expands Whale Optimization Algorithm(WOA)through the integration of sine and wormhole energy features thus improving exploration and exploitation capabilities for efficient convergence in complex non-linear OPF problems.A performance evaluation of SWEWOA takes place on the IEEE-30 bus test system through static and dynamic loading scenarios where it demonstrates better results than five contemporary algorithms:Adaptive Chaotic WOA(ACWOA),WOA,Chaotic WOA(CWOA),Sine Cosine Algorithm Differential Evolution(SCADE),and Hybrid Grey Wolf Optimization(HGWO).The research shows that SWEWOA delivers superior generation cost reduction than other algorithms by reaching a minimum of 0.9%better performance.SWEWOA demonstrates superior power loss performance by achieving(P_(loss,min))at the lowest level compared to all other tested algorithms which leads to better system energy efficiency.The dynamic loading performance of SWEWOA leads to a 4.38%reduction in gross costs which proves its capability to handle different operating conditions.The algorithm achieves top performance in Friedman Rank Test(FRT)assessments through multiple performance metrics which verifies its consistent reliability and strong stability during changing power demands.The repeated simulations show that SWEWOA generates mean costs(C_(gen,min))and mean power loss values(P_(loss,min))with small deviations which indicate its capability to maintain cost-effective solutions in each simulation run.SWEWOA demonstrates great potential as an advanced optimization solution for power system operations through the results presented in this study.展开更多
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 paper investigates wormhole solutions within the framework of extended symmetric teleparallel gravity,incorporating non-commutative geometry,and conformal symmetries.To achieve this,we examine the linear wormhole...This paper investigates wormhole solutions within the framework of extended symmetric teleparallel gravity,incorporating non-commutative geometry,and conformal symmetries.To achieve this,we examine the linear wormhole model with anisotropic fluid under Gaussian and Lorentzian distributions.The primary objective is to derive wormhole solutions while considering the influence of the shape function on model parameters under Gaussian and Lorentzian distributions.The resulting shape function satisfies all the necessary conditions for a traversable wormhole.Furthermore,we analyze the characteristics of the energy conditions and provide a detailed graphical discussion of the matter contents via energy conditions.Additionally,we explore the effect of anisotropy under Gaussian and Lorentzian distributions.Finally,we present our conclusions based on the obtained results.展开更多
In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utiliz...In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utilizing two newly developed shape functions(SF)that satisfy all basic conditions for a WH’s physical validity.We also observe that the null energy condition(NEC)behaves negatively.Finally,for both models,we use the volume integral quantifier(VIQ)and Tolman-Oppenheimer-Volkoff(TOV)equation to determine how much exotic matter is needed near the WH throat and the stability of the WH.The extensive detailed discussions of the matter components have been done via graphical analysis.The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.展开更多
In the background of f(R,L_(m))gravity,this work investigates three distinct dark matter halo profiles to test the possibility of generalised wormhole geometry within the galactic halo regions.The current study aims t...In the background of f(R,L_(m))gravity,this work investigates three distinct dark matter halo profiles to test the possibility of generalised wormhole geometry within the galactic halo regions.The current study aims to accomplish these goals by examining various dark matter profiles including universal rotation curves(URC),Navarro-Frenk-White(NFW)model-Ⅰ,and NFW model-Ⅱinside two distinct f(R,L_(m))gravity models.According to the f(R,L_(m))=R/2+L^(a)_(m)model,the dark matter(DM)halo density profiles produce suitable shape functions that meet all the necessary requirements for exhibiting the wormhole geometries with appropriate choice of free parameters.In addition,to examine DM profiles under the f(R,L_(m))=R/2+(1+λR)L_(m) model,we consider a specific shape function.Further,we observed that the derived solution from both two models violates the null energy constraints,confirming that the DM supports wormholes to maintain in the galactic halo.展开更多
The main objective of this paper is to reveal the evolving traversable wormhole solutions in the context of modified f(R,G)gravity,which affects the gravitational interaction.These results are derived by applying the ...The main objective of this paper is to reveal the evolving traversable wormhole solutions in the context of modified f(R,G)gravity,which affects the gravitational interaction.These results are derived by applying the Karmarkar condition,which creates wormhole geometry that meets the necessary conditions and connects two asymptotically flat areas of spacetime.The proposed study's main goal is to construct the wormhole structures by splitting the f(R,G)gravity model into two forms Firstly,we split the model into an exponential-like f(R)gravity model and a power law f(G)gravity model,and secondly,we consider the Starobinsky f(R)gravity model along with a power law f(G)gravity model.Besides,we address the feasibility of shape functions and the structural analysis of wormhole structures for specific models.These models are then confined to be compatible with current experimental evidence.Further,the energy conditions of the wormhole are geometrically probed,and it is proven that they adhere to the null energy conditions in areas close to the throat.Moreover,the fascinating aspect of this study involves conducting an examination and comparison of evolving wormhole geometries in the vicinity of the throat in our chosen models,utilizing two-and three-dimensional graphical representations.We observe that our shape function acquired through the Karmarkar technique yields validated wormhole configurations with even less exotic matter,correlating to the proper choice of f(R,G)gravity models and acceptable free parameter values.In summary,we conclude that our findings meet all the criteria for the existence of wormholes,affirming the viability and consistency of our study.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
Wormhole attack is one of the most devastating threats for range-free localization in wireless sensor networks. In this paper, we evaluate three statistical estimation methods with the same network model and geographi...Wormhole attack is one of the most devastating threats for range-free localization in wireless sensor networks. In this paper, we evaluate three statistical estimation methods with the same network model and geographic information obtailaed by the DV-Hop algorithm. We analyze the limits of Minimum Mean Square Estimate （MMSE）, Least Median of Squares （LMS） and Enhanced greedy At- tack-Resistant MMSE （EARMMSE） and propose an improved EARMMSE with the hop-distance relationship, named EARMMSE＋. Simulation results illustrate the performance of MMSE, LMS and EARMMSE＋ with different anchor fraction, the length of wormhole link and the average local neighborhood and show that EARMMSE＋ outperforms MMSE and LMS.展开更多
An IoT-based wireless sensor network(WSN)comprises many small sensors to collect the data and share it with the central repositories.These sensors are battery-driven and resource-restrained devices that consume most o...An IoT-based wireless sensor network(WSN)comprises many small sensors to collect the data and share it with the central repositories.These sensors are battery-driven and resource-restrained devices that consume most of the energy in sensing or collecting the data and transmitting it.During data sharing,security is an important concern in such networks as they are prone to many threats,of which the deadliest is the wormhole attack.These attacks are launched without acquiring the vital information of the network and they highly compromise the communication,security,and performance of the network.In the IoT-based network environment,its mitigation becomes more challenging because of the low resource availability in the sensing devices.We have performed an extensive literature study of the existing techniques against the wormhole attack and categorised them according to their methodology.The analysis of literature has motivated our research.In this paper,we developed the ESWI technique for detecting the wormhole attack while improving the performance and security.This algorithm has been designed to be simple and less complicated to avoid the overheads and the drainage of energy in its operation.The simulation results of our technique show competitive results for the detection rate and packet delivery ratio.It also gives an increased throughput,a decreased end-to-end delay,and a much-reduced consumption of energy.展开更多
This analysis explores the new wormhole(WH)solution in the background of teleparallel gravity with minimal matter coupling.To complete this study,we consider the conformal symmetry with non-zero Killing vectors.The ex...This analysis explores the new wormhole(WH)solution in the background of teleparallel gravity with minimal matter coupling.To complete this study,we consider the conformal symmetry with non-zero Killing vectors.The exact shape function is computed by considering the linear equation of state with the phantom regime.The energy conditions are investigated for the calculated shape function with the equation of state parameter.The presence of exotic matter is confirmed due to the violation of the null energy condition.The current study also explores the physical properties of the epicyclic frequencies with quasi-periodic oscillations.In the astrophysical,epicyclic frequencies are extensively employed to explore the self-gravitating system.It is concluded that a stable WH solution is acceptable for WH geometry.展开更多
As the applications of wireless sensor networks(WSNs) diversify,providing secure communication is emerging as a critical requirement. In this paper,we investigate the detection of wormhole attack,a serious security is...As the applications of wireless sensor networks(WSNs) diversify,providing secure communication is emerging as a critical requirement. In this paper,we investigate the detection of wormhole attack,a serious security issue for WSNs. Wormhole attack is difficult to detect and prevent,as it can work without compromising sensor nodes or breaching the encryption key. We present a wormhole attack detection approach based on the probability distribution of the neighboring-node-number,WAPN,which helps the sensor nodes to judge distributively whether a wormhole attack is taking place and whether they are in the in-fluencing area of the attack. WAPN can be easily implemented in resource-constrained WSNs without any additional requirements,such as node localization,tight synchronization,or directional antennas. WAPN uses the neighboring-node-number as the judging criterion,since a wormhole usually results in a significant increase of the neighboring-node-number due to the extra attacking link. Firstly,we model the distribution of the neighboring-node-number in the form of a Bernoulli distribution. Then the model is simplified to meet the sensor nodes' constraints in computing and memory capacity. Finally,we propose a simple method to obtain the threshold number,which is used to detect the existence of a wormhole. Simulation results show that WAPN is effective under the conditions of different network topologies and wormhole parameters.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
Wireless sensor networks (WSNs) consist of a large number of sensor nodes that monitor the environment and a few base stations that collect the sensor readings. Individual sensor nodes are subject to compromised secur...Wireless sensor networks (WSNs) consist of a large number of sensor nodes that monitor the environment and a few base stations that collect the sensor readings. Individual sensor nodes are subject to compromised security because they may be deployed in hostile environments and each sensor node communicates wirelessly. An adversary can inject false reports into the networks via compromised nodes. Furthermore, an adversary can create a wormhole by directly linking two compromised nodes or using out-of-band channels. If these two kinds of attacks occur simultaneously in a network, existing methods cannot defend against them adequately. We thus propose a secure routing method for detecting false report injections and wormhole attacks in wireless sensor networks. The proposed method uses ACK messages for detecting wormholes and is based on a statistical en-route filtering (SEF) scheme for detecting false reports. Simulation results show that the proposed method reduces energy consumption by up to 20% and provide greater network security.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
OLSR （optimal link state routing） is one of the four basic routing protocols used in mobile ad hoe Networks by the MANET working group of IETF（Internet engineering task force）. OLSR, a proactive routing protocol, ...OLSR （optimal link state routing） is one of the four basic routing protocols used in mobile ad hoe Networks by the MANET working group of IETF（Internet engineering task force）. OLSR, a proactive routing protocol, is based on a multipoint relaying flooding technique to reduce the number of topology broadcast. OLSR uses periodic HELLO packets to neighbor detection. As introduced in Reference [1], the wormhole attack can form a serious threat in wireless Networks, especially against many ad hoc Network routing protocols and location-based wireless security systems. Here, a trust model to handle this attack in OLSR is provided and simulated in NS2.展开更多
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The Sine and Wormhole Energy Whale Optimization Algorithm(SWEWOA)represents an advanced solution method for resolving Optimal Power Flow(OPF)problems in power systems equipped with Flexible AC Transmission System(FACTS)devices which include Thyristor-Controlled Series Compensator(TCSC),Thyristor-Controlled Phase Shifter(TCPS),and Static Var Compensator(SVC).SWEWOA expands Whale Optimization Algorithm(WOA)through the integration of sine and wormhole energy features thus improving exploration and exploitation capabilities for efficient convergence in complex non-linear OPF problems.A performance evaluation of SWEWOA takes place on the IEEE-30 bus test system through static and dynamic loading scenarios where it demonstrates better results than five contemporary algorithms:Adaptive Chaotic WOA(ACWOA),WOA,Chaotic WOA(CWOA),Sine Cosine Algorithm Differential Evolution(SCADE),and Hybrid Grey Wolf Optimization(HGWO).The research shows that SWEWOA delivers superior generation cost reduction than other algorithms by reaching a minimum of 0.9%better performance.SWEWOA demonstrates superior power loss performance by achieving(P_(loss,min))at the lowest level compared to all other tested algorithms which leads to better system energy efficiency.The dynamic loading performance of SWEWOA leads to a 4.38%reduction in gross costs which proves its capability to handle different operating conditions.The algorithm achieves top performance in Friedman Rank Test(FRT)assessments through multiple performance metrics which verifies its consistent reliability and strong stability during changing power demands.The repeated simulations show that SWEWOA generates mean costs(C_(gen,min))and mean power loss values(P_(loss,min))with small deviations which indicate its capability to maintain cost-effective solutions in each simulation run.SWEWOA demonstrates great potential as an advanced optimization solution for power system operations through the results presented in this study.
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DST,New Delhi,India,for its financial support for research facilities under DSTFIST-2019。
文摘This paper investigates wormhole solutions within the framework of extended symmetric teleparallel gravity,incorporating non-commutative geometry,and conformal symmetries.To achieve this,we examine the linear wormhole model with anisotropic fluid under Gaussian and Lorentzian distributions.The primary objective is to derive wormhole solutions while considering the influence of the shape function on model parameters under Gaussian and Lorentzian distributions.The resulting shape function satisfies all the necessary conditions for a traversable wormhole.Furthermore,we analyze the characteristics of the energy conditions and provide a detailed graphical discussion of the matter contents via energy conditions.Additionally,we explore the effect of anisotropy under Gaussian and Lorentzian distributions.Finally,we present our conclusions based on the obtained results.
基金S Chaudhary expresses his gratitude to the Central University of Haryana for providing a University Research Fellowship (URF) under the Reg. No. 222019the Department of Mathematics, Central University of Haryanathe University Grant Commission (UGC), New Delhi, India under the NTA Ref. No. 211610000030 for providing financial support
文摘In this work,we have explored wormhole(WH)solutions in F(R,L_(m))gravity by assuming the Morris-Thorne WH metric and F(R,Lm)=R/2+(1+γR)L_(m),whereγis the free model parameter.We determined the WH solutions by utilizing two newly developed shape functions(SF)that satisfy all basic conditions for a WH’s physical validity.We also observe that the null energy condition(NEC)behaves negatively.Finally,for both models,we use the volume integral quantifier(VIQ)and Tolman-Oppenheimer-Volkoff(TOV)equation to determine how much exotic matter is needed near the WH throat and the stability of the WH.The extensive detailed discussions of the matter components have been done via graphical analysis.The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.
基金University Grant Commission(UGC),Govt.of India,New Delhi,for awarding JRF(NTA Ref.No.:191620024300)University Grants Commission(UGC),New Delhi,India,for awarding National Fellowship for Scheduled Caste Students(UGC-Ref.No.:201610123801)+1 种基金PKS acknowledges the National Board for Higher Mathematics(NBHM)under the Department of Atomic Energy(DAE),Govt.of India,for financial support to carry out the Research project No.:02011/3/2022 NBHM(R.P.)/R&D II/2152 Dt.14.02.2022IUCAA,Pune,India for providing support through the visiting Associateship program.
文摘In the background of f(R,L_(m))gravity,this work investigates three distinct dark matter halo profiles to test the possibility of generalised wormhole geometry within the galactic halo regions.The current study aims to accomplish these goals by examining various dark matter profiles including universal rotation curves(URC),Navarro-Frenk-White(NFW)model-Ⅰ,and NFW model-Ⅱinside two distinct f(R,L_(m))gravity models.According to the f(R,L_(m))=R/2+L^(a)_(m)model,the dark matter(DM)halo density profiles produce suitable shape functions that meet all the necessary requirements for exhibiting the wormhole geometries with appropriate choice of free parameters.In addition,to examine DM profiles under the f(R,L_(m))=R/2+(1+λR)L_(m) model,we consider a specific shape function.Further,we observed that the derived solution from both two models violates the null energy constraints,confirming that the DM supports wormholes to maintain in the galactic halo.
基金National University of Computer and Emerging Sciences(NUCES)for funding support through research reward programmethe Grant No.YS304023912 to support his Postdoctoral Fellowship at Zhejiang Normal University,China。
文摘The main objective of this paper is to reveal the evolving traversable wormhole solutions in the context of modified f(R,G)gravity,which affects the gravitational interaction.These results are derived by applying the Karmarkar condition,which creates wormhole geometry that meets the necessary conditions and connects two asymptotically flat areas of spacetime.The proposed study's main goal is to construct the wormhole structures by splitting the f(R,G)gravity model into two forms Firstly,we split the model into an exponential-like f(R)gravity model and a power law f(G)gravity model,and secondly,we consider the Starobinsky f(R)gravity model along with a power law f(G)gravity model.Besides,we address the feasibility of shape functions and the structural analysis of wormhole structures for specific models.These models are then confined to be compatible with current experimental evidence.Further,the energy conditions of the wormhole are geometrically probed,and it is proven that they adhere to the null energy conditions in areas close to the throat.Moreover,the fascinating aspect of this study involves conducting an examination and comparison of evolving wormhole geometries in the vicinity of the throat in our chosen models,utilizing two-and three-dimensional graphical representations.We observe that our shape function acquired through the Karmarkar technique yields validated wormhole configurations with even less exotic matter,correlating to the proper choice of f(R,G)gravity models and acceptable free parameter values.In summary,we conclude that our findings meet all the criteria for the existence of wormholes,affirming the viability and consistency of our study.
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.
基金Acknov,.4edgements This work was supported in part by National Basic Research Program of China （＂973 program＂） under contract No. 2007CB307101, and in part by National Natural Science Foundation of China under Grant No. 60833002, No. 60802016 and No.60972010.
文摘Wormhole attack is one of the most devastating threats for range-free localization in wireless sensor networks. In this paper, we evaluate three statistical estimation methods with the same network model and geographic information obtailaed by the DV-Hop algorithm. We analyze the limits of Minimum Mean Square Estimate （MMSE）, Least Median of Squares （LMS） and Enhanced greedy At- tack-Resistant MMSE （EARMMSE） and propose an improved EARMMSE with the hop-distance relationship, named EARMMSE＋. Simulation results illustrate the performance of MMSE, LMS and EARMMSE＋ with different anchor fraction, the length of wormhole link and the average local neighborhood and show that EARMMSE＋ outperforms MMSE and LMS.
文摘An IoT-based wireless sensor network(WSN)comprises many small sensors to collect the data and share it with the central repositories.These sensors are battery-driven and resource-restrained devices that consume most of the energy in sensing or collecting the data and transmitting it.During data sharing,security is an important concern in such networks as they are prone to many threats,of which the deadliest is the wormhole attack.These attacks are launched without acquiring the vital information of the network and they highly compromise the communication,security,and performance of the network.In the IoT-based network environment,its mitigation becomes more challenging because of the low resource availability in the sensing devices.We have performed an extensive literature study of the existing techniques against the wormhole attack and categorised them according to their methodology.The analysis of literature has motivated our research.In this paper,we developed the ESWI technique for detecting the wormhole attack while improving the performance and security.This algorithm has been designed to be simple and less complicated to avoid the overheads and the drainage of energy in its operation.The simulation results of our technique show competitive results for the detection rate and packet delivery ratio.It also gives an increased throughput,a decreased end-to-end delay,and a much-reduced consumption of energy.
基金Grant No.ZC304022919 to support his Postdoctoral Fellowship at Zhejiang Normal University,P.R.China。
文摘This analysis explores the new wormhole(WH)solution in the background of teleparallel gravity with minimal matter coupling.To complete this study,we consider the conformal symmetry with non-zero Killing vectors.The exact shape function is computed by considering the linear equation of state with the phantom regime.The energy conditions are investigated for the calculated shape function with the equation of state parameter.The presence of exotic matter is confirmed due to the violation of the null energy condition.The current study also explores the physical properties of the epicyclic frequencies with quasi-periodic oscillations.In the astrophysical,epicyclic frequencies are extensively employed to explore the self-gravitating system.It is concluded that a stable WH solution is acceptable for WH geometry.
文摘As the applications of wireless sensor networks(WSNs) diversify,providing secure communication is emerging as a critical requirement. In this paper,we investigate the detection of wormhole attack,a serious security issue for WSNs. Wormhole attack is difficult to detect and prevent,as it can work without compromising sensor nodes or breaching the encryption key. We present a wormhole attack detection approach based on the probability distribution of the neighboring-node-number,WAPN,which helps the sensor nodes to judge distributively whether a wormhole attack is taking place and whether they are in the in-fluencing area of the attack. WAPN can be easily implemented in resource-constrained WSNs without any additional requirements,such as node localization,tight synchronization,or directional antennas. WAPN uses the neighboring-node-number as the judging criterion,since a wormhole usually results in a significant increase of the neighboring-node-number due to the extra attacking link. Firstly,we model the distribution of the neighboring-node-number in the form of a Bernoulli distribution. Then the model is simplified to meet the sensor nodes' constraints in computing and memory capacity. Finally,we propose a simple method to obtain the threshold number,which is used to detect the existence of a wormhole. Simulation results show that WAPN is effective under the conditions of different network topologies and wormhole parameters.
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Wireless sensor networks (WSNs) consist of a large number of sensor nodes that monitor the environment and a few base stations that collect the sensor readings. Individual sensor nodes are subject to compromised security because they may be deployed in hostile environments and each sensor node communicates wirelessly. An adversary can inject false reports into the networks via compromised nodes. Furthermore, an adversary can create a wormhole by directly linking two compromised nodes or using out-of-band channels. If these two kinds of attacks occur simultaneously in a network, existing methods cannot defend against them adequately. We thus propose a secure routing method for detecting false report injections and wormhole attacks in wireless sensor networks. The proposed method uses ACK messages for detecting wormholes and is based on a statistical en-route filtering (SEF) scheme for detecting false reports. Simulation results show that the proposed method reduces energy consumption by up to 20% and provide greater network security.
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.
基金Supported by the Natural Science Foundation of Hubei Province(No.2005ABA243) .
文摘OLSR （optimal link state routing） is one of the four basic routing protocols used in mobile ad hoe Networks by the MANET working group of IETF（Internet engineering task force）. OLSR, a proactive routing protocol, is based on a multipoint relaying flooding technique to reduce the number of topology broadcast. OLSR uses periodic HELLO packets to neighbor detection. As introduced in Reference [1], the wormhole attack can form a serious threat in wireless Networks, especially against many ad hoc Network routing protocols and location-based wireless security systems. Here, a trust model to handle this attack in OLSR is provided and simulated in NS2.
