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.

Thin-shell wormholes and modified Chaplygin gas with relativistic corrections

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.

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.

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.

Exploration of Traversable Wormholes Sustained by an Extra Spatial Dimension

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.

Observational appearance and extra photon rings of an asymmetric thin-shell wormhole with a Bardeen profile

In this work,the optical appearance of an asymmetric thin-shell wormhole with a Bardeen profile is studied.To initiate the process,we need to construct an asymmetric thin-shell wormhole utilizing the cut-and-paste technique proposed by Visser and subsequently ascertain its pertinent physical quantities such as the radius of the photon sphere and critical impact parameters for different values of magnetic charge g.Then,the effective potential and motion behavior of photons are also investigated within the framework of asymmetric thin-shell wormholes with a Bardeen profile.It can be found that the effective potential,ray trajectory,and azimuthal angle of the thin-shell wormhole exhibit a strong correlation with the mass ratio of black holes.By considering the accretion disk as the sole background light source,we observe additional photon rings and lensing bands in the optical appearance of the asymmetric thin-shell wormhole with a Bardeen profile compared to those exhibited by the Bardeen black hole.One can find that there is an increase in the size of the specific additional light bands with increasing magnetic charge g,which is different from the black hole case.These exceptionally luminous rings can serve as a robust criterion for the identification and characterization of the thin-shell wormhole spacetime.

Effects of torsion charge on optical appearance and additional photon rings of an asymmetric thin-shell wormhole

In this paper,we study the optical properties of asymmetric thin-shell wormholes(ATWs)under torsion charge.Utilizing the cut-and-paste method developed by Visser,we construct these wormholes and determine their key physical properties,such as the radius of the photon sphere and critical impact parameters,under different torsion charges.Furthermore,we investigate the effective potential and behavior of photon motion within the wormhole spacetime,identifying a relationship between photon trajectories and impact parameters.The study focuses on scenarios where thin accretion disks act as the primary light source.It reveals that the optical features of ATWs under torsion charge significantly differ from those of black holes(BHs).Notably,an increase in torsion charge leads to a reduction in the sizes of both extra photon rings and lensing bands,which serve as important markers for distinguishing and characterizing ATW spacetimes from those of BHs.

Numerical Simulation and Experiment on Thin-Shell Object Separation from Aircraft

The unsteady aerodynamic loads generated by the thin-shell object separating from aircraft affects flying safety.To investigate the loads,a method combining numerical simulation and experiment is proposed.Firstly,the motional tendency of the thin-shell object separating from aircraft is calculated,and then the high-speed air blowing test on ground is designed.Thereafter,the external store is employed to avoid colliding with the thin-shell object in air.Finally,the hanging and flight test is conducted by a high-speed unmanned aerial vehicle(UAV),and the feasibility of the thin-shell object separating from aircraft at high speed is proved.Consequently,the separating problem of a thin-shell object with an unconventional aerodynamic configuration is solved,and the collisions with aircraft is prevented.

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.

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.

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.

Wormholes Do Not Exist: They Are Mathematical Artifacts from an Incomplete Gravitational Theory

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”.

改进的MVO-GRNN神经网络岩爆预测模型研究

准确预测岩爆烈度等级能有效指导岩爆灾害的防控。根据影响岩爆发生及烈度等级的3个因素构建岩爆评价指标体系,提出一种基于改进多元宇宙算法(Improved Multi-Verse Optimizer,IMVO)优化广义回归神经网络(General Regression Neural Network,GRNN)的岩爆预测模型。在普通多元宇宙算法(MVO)的基础上,运用自适应平衡机制调节MVO算法中的虫洞存在概率(V_(WEP))和旅行距离率(V_(TDR))两个重要参数来改进该算法;再运用改进的多元宇宙算法优化广义回归神经网络的光滑度,通过训练数据优选出最佳光滑因子σ,得到IMVO-GRNN神经网络岩爆烈度预测模型;最后结合工程实例验证模型的性能。研究表明,该模型相比传统模型寻优能力更强,精度更高,为岩爆预测提供了一种新的思路。

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．

碳酸盐岩储层酸蚀蚓孔物模实验研究进展

酸蚀蚓孔是碳酸盐岩储层基质酸化最典型、最基本的特征,其尺寸和形态对酸化效果有着重要影响,关于酸蚀蚓孔的物模研究对于碳酸盐岩储层基质酸化机理研究及现场施工设计具有重要指导意义。文章分别综述了线性流和径向流两种岩心流动实验研究的重要成果和最新进展,指出酸蚀蚓孔实时表征是线性流岩心流动实验研究的发展方向,针对渗透率、尺寸等岩心参数对酸蚀蚓孔发育的影响,应结合融合电测和示踪剂的蚓孔实时表征方法进行进一步研究。针对酸液突破岩心时孔隙体积倍数(PVBT)与岩心参数之间关系的认识,后续应进一步升级径向流岩心流动实验及表征设备,从而开展不同因素对酸蚀蚓孔发育影响的研究,重点解决酸蚀蚓孔从实验尺度升级到现场尺度问题。建议加强电测法室外模拟实验及现场应用研究,从而实现实验尺度和现场尺度酸蚀蚓孔的实时观测和表征。

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。

基于PCIE的多嵌入式人工智能处理器低延迟数据交换技术

针对多嵌入式人工智能(Artificial Intelligence,AI)处理器板卡之间的任务调度和数据交换冲突以及提高多板卡堆叠扩展时的可靠性和运行效率问题,文中提出了一种虫洞交换结构多嵌入式人工智能处理器高速数据交换技术和数据帧结构的解决方法。该方法基于PCIE(PCI Express)高速数据接口,将数据以数据单元的形式进行信息传递,并设计多重权重决策算法避免数据传输中的冲突,实现任务的并发多线程处理。搭建FPGA(Field Programmable Gate Array)平台进行设计和测试,结果表明PCIE的传输带宽利用效率达到了85%以上,数据交换延迟小于20μs,系统中断任务响应平均最大延迟时间为8.775μs。该技术适用于多处理器协同的高速交换电路,可扩展至混合PCIE和RapidIO交换电路结构。

基于双重约束机制的无线传感器网络虫洞攻击检测算法

针对无线传感器网络存在的虫洞攻击问题,提出了一种基于距离和能量双重约束机制的虫洞攻击检测算法(WAD-DEC)。在邻居发现阶段,提出了距离阈值约束原则,通过限制消息的接收距离来防止虫洞节点建立恶意邻居;在数据传输阶段,提出了加密散列密钥算法对接收的数据进行异常监测。针对异常数据,再用提出的能量阈值约束原则检测虫洞攻击并剔除虫洞节点。在仿真实验中,与AD-PSO、MCPR算法相比,所提算法在时延检测上分别降低了730 ms和440 ms,将错判率最低控制在0.15%以内,检测率最高可达97.5%。结果表明,所提算法能够有效检测出虫洞攻击,在保持高检测精度的同时能够降低检测时延,防止虫洞节点建立恶意虚假邻居,并减少恶意重播消息数量,降低网络能耗,延长网络寿命.