# Wick contraction help

i am trying to reproduce these contractions of peskin.But none of my code works. please help me out here.thank you.

 \documentclass{beamer}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{simpler-wick}
\begin{document}
$\wick{ \langle \c1 {p'},\c2{k'}|(\c2{\Bar{\psi}}\c3\psi)_x(\c1{\Bar{\psi}}\c4\psi)_y|\c4p,\c3k \rangle }$

$\wick[offset=2em]{ \langle 0|\c1 a_{k'}\c2 a_{p'}\c1 \Bar{\psi}_x \c3 \psi_x \c2 \Bar{\psi}_y \c4\psi_y \c4 a_p^{\dagger}\c3 a_k^{\dagger}|0 \rangle }$

$\wick[offset=2em]{ \langle \c1 {p'}, \c2 {k'}|(\c1 {\Bar{\psi}}\c4 \psi)_x(\c2 {\Bar{\psi}}\c3 \psi)_y|\c3 p,\c4 k \rangle }$

$\wick[offset=2em]{ \langle 0|\c1 a_{k'}\c2 a_{p'}\c2 \Bar{\psi}_x \c3 \psi_x \c1 \Bar{\psi}_y \c4\psi_y \c4 a_p^{\dagger}\c3 a_k^{\dagger}|0 \rangle }$
\end{document}


all these gives no result except this. i dont understand why.i tried to put a curly braces after each \c1 but no result been produced..:(

I made your code run through, mainly by adding curly brackets.

\documentclass{beamer}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{simpler-wick}
\begin{document}
$\wick{ \langle \c1{p'},\c2{k'}|(\c2{\Bar{\psi}}\c3\psi)_x(\c1{\Bar{\psi}}\c4\psi)_y|\c4p,\c3k \rangle }$

$\wick[offset=2em]{ \langle 0|\c1{a}_{k'}\c2{a}_{p'}\c1{\Bar{\psi}_x} \c3{\psi_x} \c2{\Bar{\psi}_y}\c4{\psi_y} \c4{a_p^{\dagger}}\c3{a_k^{\dagger}}|0 \rangle }$

$\wick[offset=2em]{ \langle \c1{p'}, \c2{k'}|(\c1{\Bar{\psi}}\c4{\psi})_x(\c2{\Bar{\psi}} \c3{\psi})_y|\c3{p},\c4{k}\rangle }$

$\wick[offset=2em]{ \langle 0|\c1{a}_{k'}\c2{a}_{p'}\c2{\Bar{\psi}_x} \c3{\psi_x} \c1{\Bar{\psi}_y} \c4{\psi_y} \c4{a_p^{\dagger}}\c3{a_k^{\dagger}}|0 \rangle }$
\end{document}


Do you really want to use these huge offsets?

• well.thank you sir.is there a better way? how would you prefer to do this? – jowadul kader Mar 9 '18 at 14:08
• anyway it will work fine.but if you have some ingenious way will be happy to see that.thank you a lot. – jowadul kader Mar 9 '18 at 14:11
• @jowadulkader I would mainly reduce the huge offsets. – marmot Mar 9 '18 at 14:13
• yes its clumsy.very clumsy – jowadul kader Mar 9 '18 at 15:48