I'm trying to define a bra-ket command so that I can easily build things like:

\langle e^+ | \gamma^\mu | e^-\rangle

At the moment I have this:

\langle #1 \| \gamma^{#2} \| #3 \rangle

but, when I have \brak(e^+, \mu, e^-) in an equation I get:


Any ideas?

  • 1
    There is the braket package which might save you some trouble – clemens Jun 14 '13 at 10:35
  • 1
    you could also use the physics-package which has \bra{} and \ket{} commands (and other useful stuff). – Peater de Xel Jun 14 '13 at 10:44

You should use


There're 3 different arguments, you can't separate them by commas.

  • Ah great - my head was still in c++ mode! – JMzance Jun 14 '13 at 10:42

Just to show a version with build in scaling:

#1 \delimsize\vert #2 \delimsize\vert #3}

\brak[\Big]{e^+}{\sum_i \mu_i }{e^-}


enter image description here

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