# How to remove Conjugate when it appears in a real-valued expression? [duplicate]

I evaluated

Refine[
Conjugate[
(-4 I kp^3 v^3 - 4 γ21 γ31 γ41 + 4 kp^2 v^2 (γ21 + γ31 + γ41 - 3 I δp))
// Expand],
(γ21 | γ31 | γ41 | kp | δp | v) ∈ Reals] // FullSimplify


and got

(* 4 (-γ21 γ31 γ41 + kp^2 v^2 (γ21 + γ31 + γ41) +
I Conjugate[kp]^2 Conjugate[v]^2 (Conjugate[kp v] + 3 Conjugate[δp])) *)


How can I remove Conjugate from my result?

• FullSimplify[ Refine[Conjugate[(-4 I kp^3 v^3 - 4 \[Gamma]21 \[Gamma]31 \[Gamma]41 + 4 kp^2 v^2 (\[Gamma]21 + \[Gamma]31 + \[Gamma]41 - 3 I \[Delta]p)) // Expand]], (\[Gamma]21 | \[Gamma]31 | \[Gamma]41 | kp | \[Delta]p | v) \[Element] Reals]
– ciao
Aug 27, 2015 at 23:33
• Since I had to copy @ciao's code above and paste it into a notebook to notice the difference, I'll just write it out explicitly: ciao is suggesting that the right placement for those domain assumptions is as an option to FullSimplify, and not within Refine (which works perfectly). This Q&A exchange must have won some prize for terseness ;-) Aug 28, 2015 at 0:28
• There is always /. Conjugate -> Identity. Use at your own risk. Aug 28, 2015 at 0:33
• Actually, this is what ComplexExpand is for: Conjugate[(-4 I kp^3 v^3-4 \[Gamma]21 \[Gamma]31 \[Gamma]41+4 kp^2 v^2 (\[Gamma]21+\[Gamma]31+\[Gamma]41-3 I \[Delta]p))//Expand]//ComplexExpand//FullSimplify
– Jens
Aug 28, 2015 at 1:05
• FullSimplify[Conjugate[-4 I kp^3 v^3 - 4 γ21 γ31 γ41 + 4 kp^2 v^2 (γ21 + γ31 + γ41 - 3 I δp)], (γ21 | γ31 | γ41 | kp | δp | v) ∈ Reals] also works well in this case, and does not require Refine or Expand. Aug 28, 2015 at 1:08