# Quick (probably easy) Latex Question

1. Nov 2, 2012

### latentcorpse

Hi,

I'm trying to write some equations in LaTeX. They are inside an align environment. My code is the following:

\begin{align*}
\omega_\mu{}^{ab}(e) &= \frac{1}{2} \eta^{ac} \eta^{bd} e^\nu_c e^\rho_d ( \Omega_{[\mu \nu] \rho} - \Omega_{[\nu \rho] \mu} + \Omega_{[\rho \mu] \nu})
\\ &= \frac{1}{2} e^{\nu a} e^{\rho b} ( \Omega_{[\mu \nu] \rho} - \Omega_{[\nu \rho] \mu} + \Omega_{[\rho \mu] \nu})
\intertext{now we use the result $\Omega_{[\mu \nu] \rho} = 2 \partial_{ \left[ \mu } e_{ \nu \right] }{}^a e_{a \rho}$ from eqn $(7.89)$}
\\ &=e^{\nu a} e^{\rho b} \left( \partial_{[\mu} e_{\nu]}{}^c e_{c \rho} - \partial_{[\nu} e_{\rho]}{}^c e_{c \mu} + \partial_{[\rho} e_{\mu]}{}^c e_{c \nu} \right)
\end{align*}

The problem is the last couple of lines where i split square brackets over two different subscripts. LaTeX doesn't like this and complains - a LOT!

So I guess my question boils down to how to write the LaTeX code for something like this:

q_{ [a } p_{ b] }

without getting lots of errors!

Thanks very much!

2. Nov 2, 2012

### Simon Bridge

Like this?
$$q_{[a} p_{b]}$$

3. Nov 2, 2012

### latentcorpse

Yes. Do I need a particular package to get that to work or something?

If you look at the chunk of code I posted above, I have used exactly what you've written but it gives me errors about not having properly closed the parenthesis

4. Nov 2, 2012

### Simon Bridge

Looking through your code I get:\begin{align}\omega_\mu{}^{ab}(e) &= \frac{1}{2} \eta^{ac} \eta^{bd} e^\nu_c e^\rho_d ( \Omega_{[\mu \nu] \rho} - \Omega_{[\nu \rho] \mu} + \Omega_{[\rho \mu] \nu}) \\ &= \frac{1}{2} e^{\nu a} e^{\rho b} ( \Omega_{[\mu \nu] \rho} - \Omega_{[\nu \rho] \mu} + \Omega_{[\rho \mu] \nu}) \\ &\ldots \text{ now we use the result \Omega_{[\mu \nu] \rho} = 2 \partial_{[ \mu } e_{ \nu] }{}^a e_{a \rho} from eqn (7.89)} \\ &=e^{\nu a} e^{\rho b} \left( \partial_{[\mu} e_{\nu]}{}^c e_{c \rho} - \partial_{[\nu} e_{\rho]}{}^c e_{c \mu} + \partial_{[\rho} e_{\mu]}{}^c e_{c \nu} \right)\end{align}
... I think I see what you want to do: you want the square brackets in the partial (in the intertext) to resize so they are bigger than the e in the second part... the trouble was when you used the \left [ ... \right ] inside separate curly brackets latex did not see where the other side to each was. i.e. {\left [}{\right ]} is not allowed and that's the only reason I can think of for wanting to use \left \right in that context.

$2\partial \left [_\nu e_\rho \right ]$ ... better?
Though it does kinda make it look like the nu belongs to the e.

I'm afraid you didn't. Take a closer look ;)

[note: that equ. reference should really be a link too - jic ;) ]

Last edited: Nov 2, 2012