1,721,389 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Physical constraints on the halo mass function
No full textWe analyse the effect of two relevant physical constraints on the mass multiplicity function of dark matter haloes in a Press-Schechter type algorithm. Considering the random walk of linear Gaussian density fluctuations as a function of the smoothing scale, we simultaneously (i) account for mass semi-positivity and (ii) avoid the `cloud-in-cloud' problem. It is shown that the former constraint implies a severe cut-off of low-mass objects, balanced by an increase on larger mass scales. The analysis is performed both for scale-free power spectra and for the standard cold dark matter (CDM) model. Our approach shows that the well-known `infrared' divergence of the standard Press-Schechter mass function is caused by unphysical, negative mass events which inevitably occur in a Gaussian distribution of density fluctuations
- …
