Coleman–de Luccia Instanton of the Second Order in a Brane World

The second order Coleman–de Luccia instanton and its action in the Randall–Sundrum type II model are investigated and the comparison with the results in Einstein’s general relativity is done in the present paper. PACS Numbers: 98.80.Cq.     

Brane World Corrections to Newton’s Law

We discuss possible variations of the effective gravitational constant with length scale, predicted by most of alternative theories of gravity and unified models of physical interactions. After giving a brief general exposition, we review in more detail the predicted corrections to Newton’s law of gravity in diverse brane world models. We consider various configurations in 5 dimensions (flat, de Sitter and AdS branes in Einstein and Einstein–Gauss–Bonnet theories, with and without induced gravity and possible incomplete graviton localization), 5D multi-brane systems and some models in higher dimensions. A common feature of all models considered is the existence of corrections to Newton’s law at small radii comparable with the bulk characteristic length: at such radii, gravity on the brane becomes effectively multidimensional. Many models contain superlight perturbation modes, which modify gravity at large scale and may be important for astrophysics and cosmology.     

A genetic algorithm with local search strategy for improved detection of community structure

On the basis of modularity optimization, a genetic algorithm is proposed to detect community structure in networks by defining a local search operator. The local search operator emphasizes two features: one is that the connected nodes in a network should be located in the same community, while the other is “local selection” inspired by the mechanisms of efficient message delivery underlying the small‐world phenomenon. The results of community detection for some classic networks, such as Ucinet and Pajek networks, indicate that our algorithm achieves better community structure than other methodologies based on modularity optimization, such as the algorithms based on betweenness analysis, simulated annealing, or Tasgin and Bingol's genetic algorithm. © 2009 Wiley Periodicals, Inc. Complexity, 2010     

WiMAX无线城域网的应用研究

在WiMAX技术和IEEE 802.16标准的基础上,研究了WiMAX无线城域网的应用;给出WiMAX无线城域网的应用领域以及具体应用设想.研究结果表明,WiMAX无线城域网的应用前景广阔.     

网格中一种小世界网络的分布式构造方法

如何有效地进行资源定位是影响网格和对等网性能的重要因素,已有的一些资源查找算法引入了小世界原理来提高定位效率和降低网络负载,但没有较好解决小世界网络的构造问题.在Kleinberg小世界模型的基础上,提出了一个小世界网络的构造方法SSWCP(Scalable Small World Construction Protocol),并给出了该方法的数学分析和实现.该方法是分布式的,不必拥有全局知识,每个结点只需维护局部视图,即可使资源定位具有小世界特征所带来的优化的时间复杂度.分析和实验结果表明,该方法具有良好的扩展性,可以提高资源查找的效率.     

SCM: Secure and accountable TLS certificate management

In classical public‐key infrastructure (PKI), the certificate authorities (CAs) are fully trusted, and the security of the PKI relies on the trustworthiness of the CAs. However, recent failures and compromises of CAs showed that if a CA is corrupted, fake certificates may be issued, and the security of clients will be at risk. As emerging solutions, blockchain‐ and log‐based PKI proposals potentially solved the shortcomings of the PKI, in particular, eliminating the weakest link security and providing a rapid remedy to CAs' problems. Nevertheless, log‐based PKIs are still exposed to split‐world attacks if the attacker is capable of presenting two distinct signed versions of the log to the targeted victim(s), while the blockchain‐based PKIs have scaling and high‐cost issues to be overcome. To address these problems, this paper presents a secure and accountable transport layer security (TLS) certificate management (SCM), which is a next‐generation PKI framework. It combines the two emerging architectures, introducing novel mechanisms, and makes CAs and log servers accountable to domain owners. In SCM, CA‐signed domain certificates are stored in log servers, while the management of CAs and log servers is handed over to a group of domain owners, which is conducted on the blockchain platform. Different from existing blockchain‐based PKI proposals, SCM decreases the storage cost of blockchain from several hundreds of GB to only hundreds of megabytes. Finally, we analyze the security and performance of SCM and compare SCM with previous blockchain‐ and log‐based PKI schemes.     

Job search website for illiterate users of Pakistan

Illiteracy is a major hurdle in socio-economic development of Pakistan. Research in the Information and Communication Technology (ICT) can help in tackling this issue by developing solutions tailored for illiterate population. The work presented within this paper proposes a job search website for illiterate population of KPK province of Pakistan. The designed website does not require any human assistance while searching a job. Moreover, the website uses culturally relevant graphical and audio content. The usability of the website is tested according to the ISO-9241-11 specification. Furthermore, we have studied the effect of the participants’ characteristics, i.e., their age, computer and mobile usage experience on the usability of the website. The results show that the participants found the website usable. Specifically, they could search suitable jobs with a minimal number of clicks and in less time as compared to the usual task completion rates reported throughout the literature. None of the participants’ characteristics were found to be affecting the usability of the website. These results suggest a promising potential of ICT solutions for providing services to illiterate population of Pakistan.     

凝聚态物理学中的基本概念

本文首先根据物质世界的层次化来说明凝聚态物理学在当今物理学中所处的地位,并阐述了复杂与简单的辨证关系,来说明为何这一学科至今仍然富有生命力;进而对这一学科的范围进行了讨论,强调了位形空间和动量空间中都存在多种类型的凝聚现象,而相应的凝聚体构成了这一学科的研究对象;还探讨了处理凝聚态理论问题的量子物理与经典物理方法有效领域的界限与分野;最终对此学科的发展历史进行回顾,并追溯和剖析了其概念全系的演变,     

Beltrami—McKeon—Schubert Realizations of osp(1|4) Algebra and Possible Supersymmetric Kinematics

The possible supersymmetric kinematics are presented by the contraction method in different limits from Beltrami—McKeon—Schubert realizations of osp(1|4). The connections among the superalgebras are established. The comparison with the superalgebras contracted from Beltrami—Ivanov—Sorini realization is made.