36,110 research outputs found
Microscopic evolution of social networks
We present a detailed study of network evolution by analyzing four large online social networks with full temporal information about node and edge arrivals. For the first time at such a large scale, we study individual node arrival and edge creation processes that collectively lead to macroscopic properties of networks. Using a methodology based on the maximum-likelihood principle, we investigate a wide variety of network formation strategies, and show that edge locality plays a critical role in evolution of networks. Our findings supplement earlier network models based on the inherently non-local preferential attachment. Based on our observations, we develop a complete model of network evolution, where nodes arrive at a prespecified rate and select their lifetimes. Each node then independently initiates edges according to a “gap” process, selecting a destination for each edge according to a simple triangle-closing model free of any parameters. We show analytically that the combination of the gap distribution with the node lifetime leads to a power law out-degree distribution that accurately reflects the true network in all four cases. Finally, we give model parameter settings that allow automatic evolution and generation of realistic synthetic networks of arbitrary scale
Evolution of the digital society reveals balance between viral and mass media influence
Online social networks (OSNs) enable researchers to study the social universe
at a previously unattainable scale. The worldwide impact and the necessity to
sustain their rapid growth emphasize the importance to unravel the laws
governing their evolution. We present a quantitative two-parameter model which
reproduces the entire topological evolution of a quasi-isolated OSN with
unprecedented precision from the birth of the network. This allows us to
precisely gauge the fundamental macroscopic and microscopic mechanisms
involved. Our findings suggest that the coupling between the real pre-existing
underlying social structure, a viral spreading mechanism, and mass media
influence govern the evolution of OSNs. The empirical validation of our model,
on a macroscopic scale, reveals that virality is four to five times stronger
than mass media influence and, on a microscopic scale, individuals have a
higher subscription probability if invited by weaker social contacts, in
agreement with the "strength of weak ties" paradigm
Statistical Laws in Urban Mobility from microscopic GPS data in the area of Florence
The application of Statistical Physics to social systems is mainly related to
the search for macroscopic laws, that can be derived from experimental data
averaged in time or space,assuming the system in a steady state. One of the
major goals would be to find a connection between the statistical laws to the
microscopic properties: for example to understand the nature of the microscopic
interactions or to point out the existence of interaction networks. The
probability theory suggests the existence of few classes of stationary
distributions in the thermodynamics limit, so that the question is if a
statistical physics approach could be able to enroll the complex nature of the
social systems. We have analyzed a large GPS data base for single vehicle
mobility in the Florence urban area, obtaining statistical laws for path
lengths, for activity downtimes and for activity degrees. We show also that
simple generic assumptions on the microscopic behavior could explain the
existence of stationary macroscopic laws, with an universal function describing
the distribution. Our conclusion is that understanding the system complexity
requires dynamical data-base for the microscopic evolution, that allow to solve
both small space and time scales in order to study the transients.Comment: 17 pages, 14 figures .jpg, use imsart.cl
Modeling phase changes of road networks
Adopting an agent-based approach, this paper explores the topological evolution of road networks from a microscopic perspective. We assume a decentralized decision-making mechanism where roads are built by self-interested land parcel owners. By building roads, parcel owners hope to increase their parcelsÕ accessibility and economic value. The simulation model is performed on a grid-like land use layer with a downtown in the center, whose structure is similar to the early form of many Midwestern and Western (US) cities. The topological attributes for the networks are evaluated by multiple centrality measures such as degree centrality, closeness centrality, and betweenness centrality. Our findings disclose that the growth of road network experiences an evolutionary process where tree-like structure first emerges around the centered parcel before the network pushes outward to the periphery. In addition, road network topology undergoes obvious phase changes as the economic values of parcels vary. The results demonstrate that even without a centralized authority, road networks have the property of self-organization and evolution; furthermore, the rise-and-fall of places in terms of their economic/social values may considerably impact road network topology.road network, land parcel, network evolution, network growth, phase change
Analysis of group evolution prediction in complex networks
In the world, in which acceptance and the identification with social
communities are highly desired, the ability to predict evolution of groups over
time appears to be a vital but very complex research problem. Therefore, we
propose a new, adaptable, generic and mutli-stage method for Group Evolution
Prediction (GEP) in complex networks, that facilitates reasoning about the
future states of the recently discovered groups. The precise GEP modularity
enabled us to carry out extensive and versatile empirical studies on many
real-world complex / social networks to analyze the impact of numerous setups
and parameters like time window type and size, group detection method,
evolution chain length, prediction models, etc. Additionally, many new
predictive features reflecting the group state at a given time have been
identified and tested. Some other research problems like enriching learning
evolution chains with external data have been analyzed as well
How people make friends in social networking sites - A microscopic perspective
We study the detailed growth of a social networking site with full temporal
information by examining the creation process of each friendship relation that
can collectively lead to the macroscopic properties of the network. We first
study the reciprocal behavior of users, and find that link requests are quickly
responded to and that the distribution of reciprocation intervals decays in an
exponential form. The degrees of inviters/accepters are slightly negatively
correlative with reciprocation time. In addition, the temporal feature of the
online community shows that the distributions of intervals of user behaviors,
such as sending or accepting link requests, follow a power law with a universal
exponent, and peaks emerge for intervals of an integral day. We finally study
the preferential selection and linking phenomena of the social networking site
and find that, for the former, a linear preference holds for preferential
sending and reception, and for the latter, a linear preference also holds for
preferential acceptance, creation, and attachment. Based on the linearly
preferential linking, we put forward an analyzable network model which can
reproduce the degree distribution of the network. The research framework
presented in the paper could provide a potential insight into how the
micro-motives of users lead to the global structure of online social networks.Comment: 10 pages, 12 figures, 2 table
- …