hα: An index to quantify an individual’s scientific leadership

The $$\alpha$$ α person is the dominant person in a group. We define the $$\alpha$$ α -author of a paper as the author of the paper with the highest h-index among all the coauthors, and an $$\alpha$$ α -paper of a scientist as a paper authored or coauthored by the scientist where he/she is the $$\alpha$$ α -author. For most but not all papers in the literature there is only one $$\alpha$$ α -author. We define the $$h_\alpha$$ h α index of a scientist as the number of papers in the h-core of the scientist (i.e. the set of papers that contribute to the h-index of the scientist) where this scientist is the $$\alpha$$ α -author. We also define the $$h'_\alpha$$ h α ′ index of a scientist as the number of $$\alpha$$ α -papers of this scientist that have $$\ge$$ ≥ $$h'_\alpha$$ h α ′ citations. $$h_\alpha$$ h α and $$h'_\alpha$$ h α ′ contain similar information, while $$h'_\alpha$$ h α ′ is conceptually more appealing it is harder to obtain from existing databases, hence of less current practical interest. We propose that the $$h_\alpha$$ h α and/or $$h'_\alpha$$ h α ′ indices, or other variants discussed in the paper, are useful complements to the h-index of a scientist to quantify his/her scientific achievement, that rectify an inherent drawback of the h-index, its inability to distinguish between authors with different coauthorships patterns. A high h index in conjunction with a high $$h_\alpha /h$$ h α / h ratio is a hallmark of scientific leadership.