Questions about Abs[_]

*To*: mathgroup at smc.vnet.net*Subject*: [mg55511] Questions about Abs[_]*From*: "Steeve Brechmann \(schumi\)" <steevebrechmann at yahoo.ca>*Date*: Sun, 27 Mar 2005 02:42:44 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I define, G0[r_List, r0_List]:=(Exp[I k Norm[r-r0]/(4*Pi*Norm[r-r0]))*((1+(I/(k*Norm[r-r0]))-(1/(k^2*Norm[r-r0]^2)))*IdentityMatrix[3]-(1/Norm[r-r0]^2)*(1+((3*I)/(k*Norm[r-r0]))-(3/(k^2*Norm[r-r0]^2)))*Outer[Times,r-r0,r-r0]) where r = {x,y,z} r0={x0,y0,z0} ri={x0,y0,-z0} rsn=r0+{0,0,2*n*d} rim=ri+{0,0,2*m*d} When i want to compute G0r0rim=G0[r0,rim] I find something odd... 1) Why Abs[2*z0-2*d*m] doesn't give 2*Abs[z0-m*d] ? 2) Why Abs[2*z0-2*d*m] doesn't simplify with (2*z0-2*d*m)^2 ? Note : all the variables are positive, i.e. : z0>0, d>0 and -Infinity < m_Integer < Infinity. Steeve Brechmann Physics Department, Laval University steevebrechmann at yahoo.ca

**Follow-Ups**:**Re: Questions about Abs[_]***From:*yehuda ben-shimol <bsyehuda@gmail.com>