samedi 11 octobre 2014

Rearranging Double Summations

OK, another maths question -



This is the double sum I have:



sum_(n = 1 to infinity) n^-s sum_(n = 1 to infinity) lamda (n) mu (n) n^-s



Where lamda (n) is the Liouville function and mu (n) is the Mobius function



lamda (n) defined as lamda (1) = 1 and if n = p1^a1 . p2^a2. p3^a3... then lamda (n) = (-1)^(a1 +a2 + a3...)



and mu (n) defined as mu(1) = 1 and mu(n) = (-1)^k if a1, a2, a3.... = 1 and mu(n) = 0 otherwise. (Where n = p1^a1 . p2^a2. p3^a3...)



Anyway, this is then rearranged to give:



sum_(n = 1 to infinity) [sum (d, the divisors of n) lamda (d) mu(d) ] n^-s



This function is said to be completely multiplicative, so as to allow rearrangement, but I can't follow why one would lead to the other. Any ideas on this - or any good online resources - I've searched but not found anything so far.



Many thanks! :)




Aucun commentaire:

Enregistrer un commentaire