atom sizes 

about 50% of atoms contain just one prefix
largest atom contains over 2200 prefixes
size distribution is close to Weibull curve or power fn
address space size distribution more Kantor-like
ramified atom
several paths to same prefix branch or loop at an AS
maps to graph with positive outdegree/cycl.# 

reducing the number of atoms
focal point
AS present in all paths of atom, at same relative position
crown point
AS with largest number of following ASes among focal points
crown atom
atom whose system of AS paths has been truncated at crown point