10,849 research outputs found
Phase behavior of weakly polydisperse sticky hard spheres: Perturbation theory for the Percus-Yevick solution
We study the effects of size polydispersity on the gas-liquid phase behaviour
of mixtures of sticky hard spheres. To achieve this, the system of coupled
quadratic equations for the contact values of the partial cavity functions of
the Percus-Yevick solution is solved within a perturbation expansion in the
polydispersity, i.e. the normalized width of the size distribution. This allows
us to make predictions for various thermodynamic quantities which can be tested
against numerical simulations and experiments. In particular, we determine the
leading-order effects of size polydispersity on the cloud curve delimiting the
region of two-phase coexistence and on the associated shadow curve; we also
study the extent of size fractionation between the coexisting phases. Different
choices for the size-dependence of the adhesion strengths are examined
carefully; the Asakura-Oosawa model of a mixture of polydisperse colloids and
small polymers is studied as a specific example.Comment: 43 pages, 12 figures, and 1 tabl
The Emergence of Norms via Contextual Agreements in Open Societies
This paper explores the emergence of norms in agents' societies when agents
play multiple -even incompatible- roles in their social contexts
simultaneously, and have limited interaction ranges. Specifically, this article
proposes two reinforcement learning methods for agents to compute agreements on
strategies for using common resources to perform joint tasks. The computation
of norms by considering agents' playing multiple roles in their social contexts
has not been studied before. To make the problem even more realistic for open
societies, we do not assume that agents share knowledge on their common
resources. So, they have to compute semantic agreements towards performing
their joint actions. %The paper reports on an empirical study of whether and
how efficiently societies of agents converge to norms, exploring the proposed
social learning processes w.r.t. different society sizes, and the ways agents
are connected. The results reported are very encouraging, regarding the speed
of the learning process as well as the convergence rate, even in quite complex
settings
Two-dimensional ranking of Wikipedia articles
The Library of Babel, described by Jorge Luis Borges, stores an enormous
amount of information. The Library exists {\it ab aeterno}. Wikipedia, a free
online encyclopaedia, becomes a modern analogue of such a Library. Information
retrieval and ranking of Wikipedia articles become the challenge of modern
society. While PageRank highlights very well known nodes with many ingoing
links, CheiRank highlights very communicative nodes with many outgoing links.
In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we
analyze the properties of two-dimensional ranking of all Wikipedia English
articles and show that it gives their reliable classification with rich and
nontrivial features. Detailed studies are done for countries, universities,
personalities, physicists, chess players, Dow-Jones companies and other
categories.Comment: RevTex 9 pages, data, discussion added, more data at
http://www.quantware.ups-tlse.fr/QWLIB/2drankwikipedia
Coevolution of religious and political authority in Austronesian societies
Authority, an institutionalized form of social power, is one of the defining features of the large-scale societies that evolved during the Holocene. Religious and political authority have deep histories in human societies and are clearly interdependent, but the nature of their relationship and its evolution over time is contested. We purpose-built an ethnographic dataset of 97 Austronesian societies and used phylogenetic methods to address two long-standing questions about the evolution of religious and political authority: first, how these two institutions have coevolved, and second, whether religious and political authority have tended to become more or less differentiated. We found evidence for mutual interdependence between religious and political authority but no evidence for or against a long-term pattern of differentiation or unification in systems of religious and political authority. Our results provide insight into how political and religious authority have worked synergistically over millennia during the evolution of large-scale societies
Cooperation and Contagion in Web-Based, Networked Public Goods Experiments
A longstanding idea in the literature on human cooperation is that
cooperation should be reinforced when conditional cooperators are more likely
to interact. In the context of social networks, this idea implies that
cooperation should fare better in highly clustered networks such as cliques
than in networks with low clustering such as random networks. To test this
hypothesis, we conducted a series of web-based experiments, in which 24
individuals played a local public goods game arranged on one of five network
topologies that varied between disconnected cliques and a random regular graph.
In contrast with previous theoretical work, we found that network topology had
no significant effect on average contributions. This result implies either that
individuals are not conditional cooperators, or else that cooperation does not
benefit from positive reinforcement between connected neighbors. We then tested
both of these possibilities in two subsequent series of experiments in which
artificial seed players were introduced, making either full or zero
contributions. First, we found that although players did generally behave like
conditional cooperators, they were as likely to decrease their contributions in
response to low contributing neighbors as they were to increase their
contributions in response to high contributing neighbors. Second, we found that
positive effects of cooperation were contagious only to direct neighbors in the
network. In total we report on 113 human subjects experiments, highlighting the
speed, flexibility, and cost-effectiveness of web-based experiments over those
conducted in physical labs
What Should EDA Fund? Developing a Model for Pre-Assessment of Economic Development Investments
This paper describes the completion of a comprehensive study of regionalism that was conducted by a joint team of economists and economic development specialists for the Economic Development Administration (EDA). The project consisted of two main activities: an examination of the factors associated with economic development success and the creation of a practical interactive tool for EDA project assessment and comparison. Findings from surveys, interviews, and project case studies are discussed in terms of their support for a positive relationship between successful economic development efforts and factors such as leadership and private investment. Also, the authors discuss the creation of a quantitative assessment model utilizing well-known approaches such as economic impact multipliers and cluster theory. The primary contribution of this work to the existing body of EDA-focused research and evaluation literature is introducing a means of using standardized scores, also known as z-scores, to compare and assess economic development projects across both industries and regions
Mapping dynamical systems onto complex networks
A procedure to characterize chaotic dynamical systems with concepts of
complex networks is pursued, in which a dynamical system is mapped onto a
network. The nodes represent the regions of space visited by the system, while
edges represent the transitions between these regions. Parameters used to
quantify the properties of complex networks, including those related to higher
order neighborhoods, are used in the analysis. The methodology is tested for
the logistic map, focusing the onset of chaos and chaotic regimes. It is found
that the corresponding networks show distinct features, which are associated to
the particular type of dynamics that have generated them.Comment: 13 pages, 8 eps files in 5 figure
Modelling colloids with Baxter's adhesive hard sphere model
The structure of the Baxter adhesive hard sphere fluid is examined using
computer simulation. The radial distribution function (which exhibits unusual
discontinuities due to the particle adhesion) and static structure factor are
calculated with high accuracy over a range of conditions and compared with the
predictions of Percus--Yevick theory. We comment on rigidity in percolating
clusters and discuss the role of the model in the context of experiments on
colloidal systems with short-range attractive forces.Comment: 14 pages, 7 figures. (For proceedings of "Structural arrest in
colloidal systems with short-range attractive forces", Messina, December
2003
- …