MEASURING THE SIMILARITY OF SPECTRA OF MOLECULAR GRAPHS

Three measures of the similarity of the spectra of molecular graphs ar e considered. Two of them are previously known: the ''almost-isospectr ality measure'', aim, and the ''angle of isomerization'', ais. We now introduce a third such quantity-the ''vectorial isospectrality measure '', vim. The previous definitions of aim and ais are modified so as to make them applicable to arbitrary pairs of molecular graphs with equa l number of vertices. We establish relations between aim, ais & vim, a nd point out some of their other properties.