热科学和能源工程系

以色列物理学会前任主席,Bar-Ilan大学物理系教授、我校名誉教授学术报告通知

发布者:webmaster  时间:2010-09-30  浏览次数:70

日期:2003年3月27日 16:48:00
Shlomo Havlin教授的学术报告时间和地点安排如下:
1. 3月10日下午2:30-5:00,办公楼第一会议室,作题为: 《Novel Percolation Theory in
Complex Networks: Application to Internet, Protein Networks and Social Networks(新的
复杂网络逾渗理论在因特网、蛋白质及社会网络中的应用) 》的学术报告。
ABSTRACT:
It is found that many networks in the world such as telephone, flight, communication, social and
Internet networks do not behave like regular networks where each node is connected via links to a
typical number of nodes. Instead, in such networks, which are called, scale free networks, there is
no characteristic number of links per node, but a very broad distribution of links exists. It is shown
that many physical properties become anomalous on such networks. In particular, we study,
using percolation theory, the stability of of such networks under both random breakdown of nodes
and intentional attack on the highest connected nodes. We focus on scale free networks, such as
the Internet, and show that it is resilient to random breakdown [1], but very sensitive to
intentional attack [2]. We also describe the behavior of the network near the percolation phase
transition and show that the critical exponents are influenced by the scale free nature of the
network.
References:
[1] Resilience of the Internet to random breakdown
R. Cohen, K. Erez, D. ben-Avraham and S. Havlin
Phys. Rev. Lett. 85, 4626 (2000)
[2] Breakdown of the Internet under intentional attack
R. Cohen, K. Erez, D. ben-Avraham and S. Havlin
Phys. Rev. Lett. 86, 3682 (2001)

2. 3月11日下午3:00-5:00,力学一楼五层十三系会议室(504),作题为:
《Scaling Approach to the Question of Global Warming (利用标度律方法研究全球变暖问
题)》的学术报告。
ABSTRACT:
We test the scaling performance of seven leading global climate models by using detrended
fluctuation analysis. We analyse temperature records of six representative sites around the globe
simulated by the models, for two different scenarios: (i) with greenhouse gas forcing only and (ii)
with greenhouse gas plus aerosol forcing. We find that the simulated records for both scenarios
fail to reproduce the universal scaling behavior of the observed records, and display wide
performance differences. The deviations from the scaling behavior are more pronounced in the
first scenario, where also the trends are clearly overestimated. Since the models underestimate the
long-range persistence of the atmosphere and overestimate the trends, our analysis suggests that
the anticipated global warming is also overestimated by the models.