Hello !! As far as I know, and I do not know much about such aspects of Graph Theory, I would say that it makes no difference really... This polynomial is of interest for its roots (eigenvalues), which do not change when taking the opposite. By the way, the Mathematica page [1] gives an odd answer : "the characteristic polynomial is the right hand side of the following equation", which funnily is an elaborate way to say "its sign does not matter" :-D
I am adding Jason in Cc, as he is likely to be much more knowledgeable on the subject :-) Nathann [1] http://mathworld.wolfram.com/CharacteristicPolynomial.html -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
