  The goal of the study is to determine the underlying processes leading to the
observed collaborator distribution in modern scientific fields, with special
attention to non-power law behavior. Nanoscience is used as a case study of a
modern interdisciplinary field, and its coauthorship network for 2000-04 period
is constructed from NanoBank database. We find three collaboration modes that
correspond to three distinct ranges in the distribution of collaborators: (1)
for authors with fewer than 20 collaborators (the majority) preferential
attachment does not hold and they form a log-normal "hook" instead of a power
law, (2) authors with more than 20 collaborators benefit from preferential
attachment and form a power law tail, and (3) authors with between 250 and 800
collaborators are more frequent than expected because of the hyperauthorship
practices in certain subfields.
