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PACS Used to Study Physics Community Network Evolution

June 25, 2010

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AIP has been developing PACS for over 40 years by dedicating significant resources. PACS has been aiding the publishing efforts, in a number of ways, of almost 180 physics journals. Now a group of researchers from Los Alamos National Laboratory and University of Maryland use the PACS assigned to published articles in APS journals to map the evolution of physics topics over the period 1985 to 2006.

Journal articles get a bunch of codes assigned as part of indexing. The first two digits of the PACS codes represent the subject areas or disciplines or scientific fields (see a full list by expanding all the + signs on this page). The authors consider two disciplines to be linked in a network if two PACS codes are assigned simultaneously in the journal articles. They are thus able to construct the following networks for 1977 (top) and 2005 (bottom) respectively. In both illustrations nodes corresponding to scientific fields, as well as node labels and their corresponding fields, are shown in the same color. The size of the nodes corresponds to the number of PACS codes contained in that community. Same-color neighboring nodes have the same label. The thickness (weight) of the edges correspond to the number of shared PACS codes between communities. The thickness of the links indicates how many papers have PACS codes corresponding to both nodes.

What the study tells us is that the physics network communities are not static. Communities regularly merge and create new groups of ideas. That is to be expected from anecdotal evidence. However the authors expect their study to help in making predictions about the future of science and thus inform efforts to guide its development.

Science network maps are increasing in popularity both because of their visual appeal and prediction making. Online citation maps following references in published articles are the old fashioned simple ones but the more complex and new studies apply statistical mechanics. One such study that generated a lot of interest recently is the click stream map of science (this article was viewed/downloaded more than 20 thousand times within the first month of publication and appeared in the same journal as the PACS study).

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