Who was Where, When? Spatiotemporal Analysis of Researcher Mobility in Nuclear Science

With the emergence and growth of digital libraries, information on collaboration among researchers has become very precise in terms of time and space. Digital libraries are increasingly used for extraction of co-authorship networks where two authors are connected by an edge if they have co-authored at least one paper. Co-authorship networks that span multiple years of research publications are 'spatially-embedded dynamic networks' because each publication has supplementary information about its publishing date and the affiliation(s) of its author(s). Spatiotemporal analysis on such dynamic coauthorship networks enables us to understand the 'mobility patterns' of researchers. For instance, for each author, it is possible to identify if he/she has relocated to another institution or to another city/country by keeping track of the affiliations listed for him/her in the papers he/she has written over time. Mobility patterns provide answers to many interesting research questions such as which countries are the key influencers for other countries, how knowledge disseminates at the global level through the relocation of researchers, how collaboration patterns change over time and space as well as many others. In this paper, we focus on these research questions and perform spatiotemporal analysis on 20-year publication data in the field of nuclear physics, collected from arXiv pre-print library. Our results suggest that the USA and Germany are the countries that are most involved in nuclear physics researcher exchanges, and additional patterns of historical, geographical proximity, and language-based effects are observed in the mobility patterns of nuclear researchers across countries.