Re: Derivations on l^infinity(Z)

From: Laurent Bartholdi (laurent.bartholdi_at_epfl.ch)
Date: 08/27/04 

Date: Fri, 27 Aug 2004 16:30:02 +0000 (UTC)

Well, derivations vanish on idempotents, so they vanish on
finite-support elements.
Let chi_n denote the idempotent in l^infty(Z) with value1 at n and 0
elsewhere; take any
derivation D, and any f in l^infty(Z). then
(Df)(n)=(chi_nDf)(n)=D(chi_nf)(n)=0 for all n, so Df=0, and D=0.