222,919 research outputs found
Community Structure of the Physical Review Citation Network
We investigate the community structure of physics subfields in the citation
network of all Physical Review publications between 1893 and August 2007. We
focus on well-cited publications (those receiving more than 100 citations), and
apply modularity maximization to uncover major communities that correspond to
clearly-identifiable subfields of physics. While most of the links between
communities connect those with obvious intellectual overlap, there sometimes
exist unexpected connections between disparate fields due to the development of
a widely-applicable theoretical technique or by cross fertilization between
theory and experiment. We also examine communities decade by decade and also
uncover a small number of significant links between communities that are widely
separated in time.Comment: 14 pages, 7 figures, 8 tables. Version 2: various small additions in
response to referee comment
Network clustering and community detection using modulus of families of loops
Citation: Shakeri, H., Poggi-Corradini, P., Albin, N., & Scoglio, C. (2017). Network clustering and community detection using modulus of families of loops. Physical Review E, 95(1), 7. doi:10.1103/PhysRevE.95.012316We study the structure of loops in networks using the notion of modulus of loop families. We introduce an alternate measure of network clustering by quantifying the richness of families of (simple) loops. Modulus tries to minimize the expected overlap among loops by spreading the expected link usage optimally. We propose weighting networks using these expected link usages to improve classical community detection algorithms. We show that the proposed method enhances the performance of certain algorithms, such as spectral partitioning and modularity maximization heuristics, on standard benchmarks
The Extraction of Community Structures from Publication Networks to Support Ethnographic Observations of Field Differences in Scientific Communication
The scientific community of researchers in a research specialty is an
important unit of analysis for understanding the field specific shaping of
scientific communication practices. These scientific communities are, however,
a challenging unit of analysis to capture and compare because they overlap,
have fuzzy boundaries, and evolve over time. We describe a network analytic
approach that reveals the complexities of these communities through examination
of their publication networks in combination with insights from ethnographic
field studies. We suggest that the structures revealed indicate overlapping
sub- communities within a research specialty and we provide evidence that they
differ in disciplinary orientation and research practices. By mapping the
community structures of scientific fields we aim to increase confidence about
the domain of validity of ethnographic observations as well as of collaborative
patterns extracted from publication networks thereby enabling the systematic
study of field differences. The network analytic methods presented include
methods to optimize the delineation of a bibliographic data set in order to
adequately represent a research specialty, and methods to extract community
structures from this data. We demonstrate the application of these methods in a
case study of two research specialties in the physical and chemical sciences.Comment: Accepted for publication in JASIS
Using Machine Learning to Predict the Evolution of Physics Research
The advancement of science as outlined by Popper and Kuhn is largely
qualitative, but with bibliometric data it is possible and desirable to develop
a quantitative picture of scientific progress. Furthermore it is also important
to allocate finite resources to research topics that have growth potential, to
accelerate the process from scientific breakthroughs to technological
innovations. In this paper, we address this problem of quantitative knowledge
evolution by analysing the APS publication data set from 1981 to 2010. We build
the bibliographic coupling and co-citation networks, use the Louvain method to
detect topical clusters (TCs) in each year, measure the similarity of TCs in
consecutive years, and visualize the results as alluvial diagrams. Having the
predictive features describing a given TC and its known evolution in the next
year, we can train a machine learning model to predict future changes of TCs,
i.e., their continuing, dissolving, merging and splitting. We found the number
of papers from certain journals, the degree, closeness, and betweenness to be
the most predictive features. Additionally, betweenness increases significantly
for merging events, and decreases significantly for splitting events. Our
results represent a first step from a descriptive understanding of the Science
of Science (SciSci), towards one that is ultimately prescriptive.Comment: 24 pages, 10 figures, 4 tables, supplementary information is include
Intrinsically Dynamic Network Communities
Community finding algorithms for networks have recently been extended to
dynamic data. Most of these recent methods aim at exhibiting community
partitions from successive graph snapshots and thereafter connecting or
smoothing these partitions using clever time-dependent features and sampling
techniques. These approaches are nonetheless achieving longitudinal rather than
dynamic community detection. We assume that communities are fundamentally
defined by the repetition of interactions among a set of nodes over time.
According to this definition, analyzing the data by considering successive
snapshots induces a significant loss of information: we suggest that it blurs
essentially dynamic phenomena - such as communities based on repeated
inter-temporal interactions, nodes switching from a community to another across
time, or the possibility that a community survives while its members are being
integrally replaced over a longer time period. We propose a formalism which
aims at tackling this issue in the context of time-directed datasets (such as
citation networks), and present several illustrations on both empirical and
synthetic dynamic networks. We eventually introduce intrinsically dynamic
metrics to qualify temporal community structure and emphasize their possible
role as an estimator of the quality of the community detection - taking into
account the fact that various empirical contexts may call for distinct
`community' definitions and detection criteria.Comment: 27 pages, 11 figure
Clustering and Community Detection in Directed Networks: A Survey
Networks (or graphs) appear as dominant structures in diverse domains,
including sociology, biology, neuroscience and computer science. In most of the
aforementioned cases graphs are directed - in the sense that there is
directionality on the edges, making the semantics of the edges non symmetric.
An interesting feature that real networks present is the clustering or
community structure property, under which the graph topology is organized into
modules commonly called communities or clusters. The essence here is that nodes
of the same community are highly similar while on the contrary, nodes across
communities present low similarity. Revealing the underlying community
structure of directed complex networks has become a crucial and
interdisciplinary topic with a plethora of applications. Therefore, naturally
there is a recent wealth of research production in the area of mining directed
graphs - with clustering being the primary method and tool for community
detection and evaluation. The goal of this paper is to offer an in-depth review
of the methods presented so far for clustering directed networks along with the
relevant necessary methodological background and also related applications. The
survey commences by offering a concise review of the fundamental concepts and
methodological base on which graph clustering algorithms capitalize on. Then we
present the relevant work along two orthogonal classifications. The first one
is mostly concerned with the methodological principles of the clustering
algorithms, while the second one approaches the methods from the viewpoint
regarding the properties of a good cluster in a directed network. Further, we
present methods and metrics for evaluating graph clustering results,
demonstrate interesting application domains and provide promising future
research directions.Comment: 86 pages, 17 figures. Physics Reports Journal (To Appear
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