报告题目：Why Are There Six Degrees of Separation in a Social Network?

报告人：Prof. Stefano Boccaletti (欧洲科学院院士)

邀请人：夏昊翔 教授

报告会主持人：李先能 教授

报告时间及地点：2024年10月28日 14:30-16:00 必发9988集团B305

报告内容：

A wealth of evidence shows that real-world networks are endowed with the small-world property, i.e., that the maximal distance between any two of their nodes scales logarithmically rather than linearly with their size. In addition, most social networks are organized so that no individual is more than six connections apart from any other, an empirical regularity known as the six degrees of separation. Why social networks have this ultrasmall-world organization, whereby the graph’s diameter is independent of the network size over several orders of magnitude, is still unknown. We show that the “six degrees of separation” is the property featured by the equilibrium state of any network where individuals weigh between their aspiration to improve their centrality and the costs incurred in forming and maintaining connections. We show, moreover, that the emergence of such a regularity is compatible with all other features, such as clustering and scale-freeness, that normally characterize the structure of social networks. Thus, our results show how simple evolutionary rules of the kind traditionally associated with human cooperation and altruism can also account for the emergence of one of the most intriguing attributes of social networks.

报告人介绍：

Stefano Boccaletti教授，欧洲科学院院士，意大利国家科学院复杂系统研究所主任、终身高级研究员，入选欧盟“玛丽·居里”学者人才计划。Stefano Boccaleti于1995年在佛罗伦萨大学获得物理学博士学位，并于2015年在马德里胡安·卡洛斯国王大学获得荣誉博士学位。他在2007-2011年和2014-2018年期间担任意大利驻以色列大使馆的科学专员。他的主要科学兴趣是（1）传播媒体中的模式形成和竞争（2）混沌的控制和同步（3）复杂网络的结构和动力学。他从2013年起担任Chaos Solitons & Fractals（IF=7.8）杂志的主编。2016年当选欧洲科学院院士；2024年当选美国物理学会会士。Boccalett教授在同行评审的国际期刊上发表了352篇论文，被引用超过40000次（谷歌学术）。他的h因子是75，他的i-10指数是239。单篇论文最高引用近13300次。研究成果多次被Nature News, LiveScience, ScienceDaily, Phys.Org, Complexity Digest等科学媒体报道和转载。

Stefano Boccaletti received the PhD in Physics at the University of Florence on 1995, and a PhD honoris causa at the University Rey Juan Carlos of Madrid on 2015.

He was Scientific Attache’ of the Italian Embassy in Israel during the years 2007-2011 and 2014-2018.

He is currently Director of Research at the Institute of Complex Systems of the Italian CNR, in Florence.

His major scientific interests are i) pattern formation and competition in extended media, ii) control and synchronization of chaos, and iii) the structure and dynamics of complex networks.

He is Editor in Chief of the Journal “Chaos, Solitons and Fractals” (Elsevier) from 2013, member of the Academia Europaea since 2016, and Fellow of the American Physical Society from 2024.

He was elected member of the Florence City Council from 1995 to 1999.

Boccaletti has published 352 papers in peer-reviewed international Journals, which received more than 40,000 citations (Google Scholar). His h factor is 75 and his i-10 index is 239.

With more than 13,300 citations, the monograph ¨Complex Networks: Structure and Dynamics¨, published by Boccaletti in Physics Reports on 2006 converted into the most quoted paper ever appeared in the Annals of that Journal.