# Taking absolute value of complex variable

I'm trying to take absolute value squared of certain objects. Say I have

y=alpha


and I know that |alpha|^2 = alpha*Conjugate[alpha].

How do I take Abs[y]^2 without assigning a numerical value to alpha in mathematica?

• Depending on the form of the output desired: Clear[alpha]; Abs[alpha]^2 // ComplexExpand[#, {alpha}] & or Abs[alpha]^2 // ComplexExpand[#, {alpha}, TargetFunctions -> Conjugate] & – Bob Hanlon Apr 8 '19 at 23:15

α = αr + I*αi;

y[alpha_] := Abs[alpha]^2