Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session V33: Focus Session: Social Networks |
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Sponsoring Units: GSNP Chair: Alessandro Vespignani, Indiana University Room: Baltimore Convention Center 336 |
Thursday, March 16, 2006 11:15AM - 11:51AM |
V33.00001: Social Balance on Networks: The Dynamics of Friendship and Hatred Invited Speaker: We study the evolution of social networks that contain both friendly and unfriendly pairwise links between individual nodes. The network is endowed with dynamics in which the sense of a link in an imbalanced triad---a triangular loop with 1 or 3 unfriendly links---is reversed to make the triad balanced. Thus an imbalanced triad is analogous to a frustrated plaquette in a random magnet, while a balanced triad fulfills the adage: ``a friend of my friend is my friend; an enemy of my friend is my enemy; a friend of my enemy is my enemy; an enemy of my enemy is my friend.'' With this frustration-reducing dynamics, an infinite network undergoes a dynamic phase transition from a steady state to ``paradise''---all links are friendly---as the propensity for friendly links to be created in an update event passes through 1/2. On the other hand, a finite network always falls into a socially-balanced absorbing state where no imbalanced triads remain. A prominent example of the achievement of social balance is the evolution of pacts and treaties between various European countries during the late 1800's and early 1900's. Here social balance gave rise to the two major alliances that comprised the protagonists of World War I. [Preview Abstract] |
Thursday, March 16, 2006 11:51AM - 12:03PM |
V33.00002: Lamb-lion Problem on Networks and Its Applications Sungmin Lee, Soon-Hyung Yook, Yup Kim We numerically study the dynamic properties of diffusing lamb
captured by diffusing lion on the complex networks. We find
that the survival probability $S(t)$ of a lamb decays
exponentially on the complex networks including scale-free
networks whose degree distribution follows $P(k) \sim k^{-
\gamma}$. We also find that the average life time $ |
Thursday, March 16, 2006 12:03PM - 12:15PM |
V33.00003: Preferential attachment in the growth of social networks: the case of Wikipedia Guido Caldarelli, Andrea Capocci, Vito Servedio, Luciana Buriol, Debora Donato, Stefano Leonardi Here we present experimental data and a model in order to describe the evolution of a socio-technological system. The case of study presented is that of the online free encyclopedia Wikipedia, for which we have the complete series of pages addition during time. The varioius entries and the hyperlinks between them can be described as a graph. We find scale-invariant behaviour in the distribution of the degree and a topology similar to that of the World Wide Web. By using the information on dynamics we are able to model and reproduce the features of this system. We also find that regardless the fact that any user has the possibility of global reshape, still Wikipedia has a growth described by local rules as that of the preferential attachment. [Preview Abstract] |
Thursday, March 16, 2006 12:15PM - 12:27PM |
V33.00004: Social inertia in collaboration networks Jose J. Ramasco, Steven A. Morris This work is a study of the properties of collaboration networks employing the formalism of weighted graphs to represent their one-mode projection. The weight of the edges is directly the number of times that a partnership has been repeated. This representation allows us to define the concept of {\it social inertia} that measures thetendency of authors to keep on collaborating with previouspartners. We use a collection of empirical datasets to analyze several aspects of the social inertia: 1) its probability distribution, 2) its correlation with other properties, and 3) the correlations of the inertia between neighbors in the network. We also contrast these empirical results with the predictions of a recently proposed theoretical model for the growth of collaboration networks. [Preview Abstract] |
Thursday, March 16, 2006 12:27PM - 12:39PM |
V33.00005: Efficiently achieving consensus in scientific collaboration networks R. Dean Malmgren, Sam Seaver, Roger Guimera, Daniel Diermeier, Julio Ottino, Luis Amaral \noindent Recent work by Guimer\'a et al.~[1] indicates that successful collaborative networks are developed from a balance of new and old blood. To first approximation, the efficiency of these collaborative networks to reach consensus on a problem depends on (i) the difficulty of the problem and (ii) the fraction of time each individual spends working on his own versus interacting with his peers. We mimic problem difficulty by the likelihood that an individual obtains the correct answer, and we model social interactions by the majority rule, which is efficient even in the presence of noise [2]. We then study the asynchronous dynamics of small-world [3] and collaborative networks [1] to quantify the efficiency of empirical collaborative networks to achieve consensus. Finally, we examine how altering the balance of new and old blood affects the efficiency of collaborative networks to reach consensus. ~ ~ \noindent [1] R. Guimer\'a, B. Uzzi, J. Spiro, and L. A. N. Amaral. \emph{Science} \textbf{308}, 697--702 (2005). ~ \noindent [2] A. A. Moreira, A. Mathur, D. Diermeier, and L. A. N. Amaral. \emph{PNAS} \textbf{101}(33), 12085--12090 (2004). ~ \noindent [3] D. J. Watts and S. H. Strogatz. \emph{Nature} \textbf{393}, 440--442 (1998). [Preview Abstract] |
Thursday, March 16, 2006 12:39PM - 12:51PM |
V33.00006: A Network Analysis of Committees in the United States House of Representatives Mason Porter Network theory provides a powerful tool for the representation and analysis of complex systems of interacting agents. Here we investigate the networks of committee and subcommittee assignments in the United States House of Representatives from the 101st--108th Congresses, with committees connected according to ``interlocks'' or common membership. We examine the House's community structure using several algorithms and reveal strong links between different committees as well as the intrinsic hierarchical structure within the House as a whole. We show additionally that structural changes, including a tighter community structure, resulted from the 1994 elections, in which the Republican party earned majority status in the House for the first time in more than forty years. In this work, we combine our network theory approach with analysis of roll call votes using singular value decomposition and successfully uncover political and organizational correlations between committees in the House without the need to incorporate other political information. This is joint work with A.J. Friend, Peter Mucha, Mark Newman, and Casey Warmbrand. [Preview Abstract] |
Thursday, March 16, 2006 12:51PM - 1:03PM |
V33.00007: DIMES -- New Results from Wide-area Internet Topology Mapping Shlomo Havlin, Shai Carmi, Eran Shir, Yuval Shavitt, Scott Kirkpartrick DIMES is a distributed agent-based Internet mapping effort which at present has attracted thousands of volunteers running clients world-wide. Despite the ``law of diminishing returns'' seen when when adding agents in past mapping attempts, we find that significant amounts of new information can be found in the long tails of our measurement process. We use the k-pruning method to decompose the network into nodes with distinct roles. The analysis suggests a new picture of the AS-level Internet structure, which distinguishes a relatively large, redundantly connected core of nearly 100 ASes and two components that flow data in and out from this core. One component is fractally interconnected through peer links; the second makes direct connections to the core only. We plan to use this picture as a framework for measuring and extrapolating changes in the Internet's physical structure. Our analysis may also be relevant for estimating the function of nodes in the ``scale free'' graphs extracted from other naturally-occurring processes. [Preview Abstract] |
Thursday, March 16, 2006 1:03PM - 1:15PM |
V33.00008: Modeling search-dominated Web growth Santo Fortunato, Alessandro Flammini, Filippo Menczer, Alessandro Vespignani Our present understanding of the Web growth, beyond the large number of existing models, is very much based on the paradigm of preferential attachment, that reflects a surf-dominated Web. In fact nowadays most of the traffic on the Web goes through and is driven by search engines. This profoundly affects the dynamics behind Web growth, potentially leading to a monopolistic scenario where few nodes attract a large share of traffic and links. We propose a minimalistic model to describe the evolution of the Web based on the interaction between users and search engines. The model reproduces several characterizing properties of the topology and traffic on the Web, and explains apparently counterintuitive empirical evidences. S. Fortunato, A. Flammini, F. Menczer and A. Vespignani, School of Informatics, Indiana University ``The egalitarian effect of search engines'', http://arxiv.org/abs/cs.CY/0511005 [Preview Abstract] |
Thursday, March 16, 2006 1:15PM - 1:27PM |
V33.00009: Evidence of accelerated growth by edge copying and unfairness in the evolution of the AS level of the Internet Bruno Gon\c{c}alves, Jose Mendes It is well known that the Internet on the Autonomous System level is in constant evolution and growth. In this paper we show that for the freely available data for the period between Nov, $97$ to March, $01$ is compatible with a edge-copying model with a probability $p=0.58$. We also demonstrate that the Internet is intrinsically unfair since the nodes with higher connectivities remain the same throughout its history. [Preview Abstract] |
Thursday, March 16, 2006 1:27PM - 1:39PM |
V33.00010: Vulnerability of complex networks: Effect of traffic and geography Marc Barthelemy, Luca Dall'Asta, Alain Barrat, Alessandro Vespignani Real-world networks present different levels of complexity: the topology, the weights and the spatial properties are often non-trivial and very different from simple random assumptions. In order to understand the vulnerability to malicious attacks of such networks one has therefore to consider not only topological quantities but also weights and space. We will present results on the paradigmatic example of the airport network which is a weighted heterogeneous network with complex traffic and spatial structures. We define different measures of damage and show that different attack strategies lead to different conclusions about the vulnerability of the network. In particular, we show that strategies need to be adapted depending on the type of damage and on the geographical region considered. [Preview Abstract] |
Thursday, March 16, 2006 1:39PM - 1:51PM |
V33.00011: Network theory model of the United States Patent citation network Jan Tobochnik, Peter Erdi, Katherine Strandburg, Gabor Csardi, Laszlo Zalanyi We report results of a network theory approach to the study of the United States patent system. We model the patent citation network as a discrete time, discrete space stochastic dynamic system. From data on more than two million patents and their citations, we extract an attractiveness function, $A(k,l)$, which determines the likelihood that a patent will be cited. A(k,l) is approximately separable into a product of a function $A_k(k)$ and a function $A_l(l)$, where $k$ is the number of citations already received (in-degree) and $l$ is the age measured in patent number units. $A_l(l)$ displays a peak at low $l$ and a long power law tail, suggesting that some patented technologies have very long-term effects. $A_k(k)$ exhibits super-linear preferential attachment. The preferential attachment exponent has been increasing since 1991, suggesting that patent citations are increasingly concentrated on a relatively small number of patents. The overall average probability that a new patent will be cited by a given patent has increased slightly during the same period. [Preview Abstract] |
Thursday, March 16, 2006 1:51PM - 2:03PM |
V33.00012: The social cost of partisanship Sam Seaver, Robert Malmgren, Andre Moreira, Daniel Diermeier, Luis Amaral Implementing policies that bring an overall social benefit can be quite difficult due to the myriad of ways in which different individuals and groups may be impacted, and the variety of targets, beliefs and agendas the policy-makers themselves may have. Examples include the implementation of measures with the objective of reducing carbon dioxide emissions and the implementation of guidelines for conducting stem cell research. Here, we use an agent-based modeling approach to investigate the effects of conservatism and partisanship on the efficiency with which large populations reach consensus on the ``correct'' decision. Remarkably, we find that conservative agents do not destroy the groups' ability to reach consensus. In fact, conservatives enable the system to maintain high efficiency, even in the presence of large levels of noise. In contrast, we find that even a small number of partisans results in low efficiency, especially for large levels of noise. We conclude that while conservatism improves social outcomes, partisanship can have significant social costs. [Preview Abstract] |
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