Thin-Shell Wormholes Admitting Conformal Motions in Spacetimes of Embedding Class One

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.

Macroscopic Traversable Wormholes: Minimum Requirements

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.

基于Wormhole路由的二维Mesh上的并行k-选择

由于二维网孔机器的结构简单、规整，易于ＶＬＳＩ实现，使得它不仅成为许多理论研究的基础模型，而且还是许多并行机所采用的互连结构．Ｗｏｒｍ ｈｏｌｅ 路由技术的采用改进了二维网孔机器的通信能力．该文在带有Ｗｏｒｍ ｈｏｌｅ 路由技术的ｎ×ｎ 二维网孔机器上提出了一个时间复杂度为Ｏ（ｌｏｇ２ｎｌｏｇｌｏｇｎ）的并行ｋ－选择算法，改进了该问题在Ｓｔｏｒｅ－ａｎｄ－Ｆｏｒｗ ａｒｄ 路由技术下的时间复杂度下界Ｏ（ｎ）．据已掌握的资料，该算法为最早的、非总线连接的二维网孔机器上的、时间复杂度为对数的多项式级的ｋ－选择算法．

一种基于Wormhole Routing的寻径技术

先锋网(Pionet)是一种具有自主知识产权的网络互连结构,将介绍先锋网寻径技术———先锋信令寻径技术(Pionet Routing)。先锋网上层协议简单,实验数据显示:该网络系统效率高,适合于进行机群科学计算。

Wormhole Routing──大规模并行处理系统中的一项关键技术

本文详细介绍了基于直接网络的大规模并行计算机的ＷｏｒｍｈｏｌｅＲｏｕｔｉｎｇ的原理。Ｗｏｒｍｈｏｌｅ寻径算法以及其它与通信性能有关的技术问题。

双层二维网格结构间的Wormhole路由算法

二维网格结构由于其较好的可扩 展性而被越来越广泛地应用,因此对于二维网格结构多处理机间的数据通信,寻找一个好的路由算法也越来越重要。以Intel公司的Option Red机器为背景,分析了双层二维网格结构多处理机间的通信机制,并且针对该实际结构,根据单层二维网格结构中以Wormhole原理为基础的Unicast自适应路由算法,提出了适用于双层二维网格结构的无死锁的Wormhole路由算法。根据该算法得出的数据传输路径是无死锁的最短传输路径。

浅谈互连网络的通信与wormhole寻径

并行处理机MPP由于其良好的可扩展性和联高性能价格比,已成为实现超高性能计算的重要支持工具。MPP系统性能的发挥极大程度上依赖于互连网络的通信性能,对于并行计算来说,寻径技术是至关重要的。互连网络中采用的寻径算法决定了消息在网络中如何选取路径,其性能对网络效率的发挥起着重要作用。该文以多机系统中的各种消息寻径方式概述为背景,着重讨论wormhole消息寻径方式。

基于Wormhole的流控制新技术研究

回顾了寻径技术近年来的发展,介绍了现阶段基于的几种流控制技术,如虚拟通道流控制技术、虚拟网络Wormhole10Wormhole等。介绍了几种基于虚拟网络的自适应寻径算法。

Energy Optimised Security against Wormhole Attack in IoT-Based Wireless Sensor Networks

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.

A New Localization Scheme with Statistical Estimation against Wormhole Attack in Wireless Sensor Networks

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.

A Secure Routing Method for Detecting False Reports and Wormhole Attacks in Wireless Sensor Networks

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.

Noncommutative-Geometry Wormholes Based on the Casimir Effect

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.

The Effect of Conformal Symmetry on Charged Wormholes

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.

Noncommutative-Geometry Inspired Charged Wormholes with Low Tidal Forces

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.

Gravitational Description and Graphics of a Wormhole Structure—A Galactic Megamaximon

Using the new exact solution of Einstein and Maxwell equations in the general relativity theory, they studied the internal structure of a geometric object with a nontrivial topology, the wormhole. They showed that the galactic black hole recently discovered by astronomers and astrophysicists as the part of the Event Horizon Telescope project with the radius about 1016 cm and the mass of about 1043 g can be a wormhole almost neutralized in charge with parameters close to critical—megamaximon, the radius of its neck curvature is equal to the so-called critical radius coinciding with half of the gravitational radius.

Defending Against Wormhole Attack in OLSR

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.

Wormholes Supported by a Combination of Normal and Quintessential Matter in Einstein and Einstein-Maxwell Gravity

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.

Is the Cosmic big Trip Just a Classical Wormhole Artifact?

Starting with the original sub-quantum dark energy model, the current accelerating phase of the evolution of the universe is considered by constructing most economical cosmic models that use just general relativity and some dominating quantum effects associated with the probabilistic description of quantum physics. Two of such models are explicitly considered. They support an interpretation of dark energy in terms of the entangled energy of the universe. The model only violates the dominant energy condition quantum mechanically, that is by an amount given by the entanglement energy density, and gives rise to an asymptotically anti-de Sitter wormhole that becomes an asymptotically flat wormhole in the classical limit. It is shown that for most cosmic solutions such a wormhole does not predict any big trip phenomenon when it accretes phantom like energy.

Modified <i>f(R)</i>Gravity and Thermodynamics of Time-Dependent Wormholes at Event Horizon

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.

Traversable Wormholes and the Brouwer Fixed-Point Theorem

The Brouwer fixed-point theorem in topology states that for any continuous mapping f on a compact convex set into itself admits a fixed point, i.e., a point x0 such that f(x0) = x0. Under suitable conditions, this fixed point corresponds to the throat of a traversable wormhole, i.e., b(r0) = r0 for the shape function b = b(r). The possible existence of wormholes can therefore be deduced from purely mathematical considerations without going beyond the existing physical requirements.