7,311 research outputs found
Directed Accelerated Growth: Application in Citation Network
In many real world networks, the number of links increases nonlinearly with
the number of nodes. Models of such accelerated growth have been considered
earlier with deterministic and stochastic number of links. Here we consider
stochastic accelerated growth in a network where links are directed. With the
number of out-going links following a power law distribution, the results are
similar to the undirected case. As the accelerated growth is enhanced, the
degree distribution becomes independent of the ``initial attractiveness'', a
parameter which plays a key role in directed networks. As an example of a
directed model with accelerated growth, the citation network is considered, in
which the distribution of the number of outgoing link has an exponential tail.
The role of accelerated growth is examined here with two different growth laws.Comment: To be published in the proceedings of Statphys Kolkata V (Physica A
The citation wake of publications detects Nobel laureates' papers
For several decades, a leading paradigm of how to quantitatively assess
scientific research has been the analysis of the aggregated citation
information in a set of scientific publications. Although the representation of
this information as a citation network has already been coined in the 1960s, it
needed the systematic indexing of scientific literature to allow for impact
metrics that actually made use of this network as a whole improving on the then
prevailing metrics that were almost exclusively based on the number of direct
citations. However, besides focusing on the assignment of credit, the paper
citation network can also be studied in terms of the proliferation of
scientific ideas. Here we introduce a simple measure based on the
shortest-paths in the paper's in-component or, simply speaking, on the shape
and size of the wake of a paper within the citation network. Applied to a
citation network containing Physical Review publications from more than a
century, our approach is able to detect seminal articles which have introduced
concepts of obvious importance to the further development of physics. We
observe a large fraction of papers co-authored by Nobel Prize laureates in
physics among the top-ranked publications.Comment: 11 pages, 3 figure
Rich-club and page-club coefficients for directed graphs
Rich-club and page-club coefficients and their null models are introduced for
directed graphs. Null models allow for a quantitative discussion of the
rich-club and page-club phenomena. These coefficients are computed for four
directed real-world networks: Arxiv High Energy Physics paper citation network,
Web network (released from Google), Citation network among US Patents, and
Email network from a EU research institution. The results show a high
correlation between rich-club and page-club ordering. For journal paper
citation network, we identify both rich-club and page-club ordering, showing
that {}"elite" papers are cited by other {}"elite" papers. Google web network
shows partial rich-club and page-club ordering up to some point and then a
narrow declining of the corresponding normalized coefficients, indicating the
lack of rich-club ordering and the lack of page-club ordering, i.e. high
in-degree (PageRank) pages purposely avoid sharing links with other high
in-degree (PageRank) pages. For UC patents citation network, we identify
page-club and rich-club ordering providing a conclusion that {}"elite" patents
are cited by other {}"elite" patents. Finally, for e-mail communication network
we show lack of both rich-club and page-club ordering. We construct an example
of synthetic network showing page-club ordering and the lack of rich-club
ordering.Comment: 18 pages, 6 figure
Early identification of important patents through network centrality
One of the most challenging problems in technological forecasting is to
identify as early as possible those technologies that have the potential to
lead to radical changes in our society. In this paper, we use the US patent
citation network (1926-2010) to test our ability to early identify a list of
historically significant patents through citation network analysis. We show
that in order to effectively uncover these patents shortly after they are
issued, we need to go beyond raw citation counts and take into account both the
citation network topology and temporal information. In particular, an
age-normalized measure of patent centrality, called rescaled PageRank, allows
us to identify the significant patents earlier than citation count and PageRank
score. In addition, we find that while high-impact patents tend to rely on
other high-impact patents in a similar way as scientific papers, the patents'
citation dynamics is significantly slower than that of papers, which makes the
early identification of significant patents more challenging than that of
significant papers.Comment: 14 page
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
Modelling Aging Characteristics in Citation Networks
Growing network models with preferential attachment dependent on both age and
degree are proposed to simulate certain features of citation network noted in
\cite{red2}. In this directed network, a new node gets attached to an older
node with the probability where the degree and age of the older
node are and respectively. Several functional forms of and
have been considered. The desirable features of the citation network can
be reproduced with and with
and and with simple modifications in the growth
scheme.Comment: 6 pages, 6 figure
Google matrix of the citation network of Physical Review
We study the statistical properties of spectrum and eigenstates of the Google
matrix of the citation network of Physical Review for the period 1893 - 2009.
The main fraction of complex eigenvalues with largest modulus is determined
numerically by different methods based on high precision computations with up
to binary digits that allows to resolve hard numerical problems for
small eigenvalues. The nearly nilpotent matrix structure allows to obtain a
semi-analytical computation of eigenvalues. We find that the spectrum is
characterized by the fractal Weyl law with a fractal dimension .
It is found that the majority of eigenvectors are located in a localized phase.
The statistical distribution of articles in the PageRank-CheiRank plane is
established providing a better understanding of information flows on the
network. The concept of ImpactRank is proposed to determine an influence domain
of a given article. We also discuss the properties of random matrix models of
Perron-Frobenius operators.Comment: 25 pages. 17 figures. Published in Phys. Rev.
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