After installing the markdown editor with LaTex
https://github.com/thibaultduponchelle/q2a-markdown-editor-latex
writing math worked nicely, until I tried to use the
\begin{array}
\end{array}
environment , for example as in this question:
Looking at $5D$ Kaluza-Klein theory, the Kaluza-Klein metric is given by
$$
g_{mn} = \left(
\begin{array}{cc}
g_{\mu\nu} & g_{\mu 5} \\
g_{5\nu} & g_{55} \\
\end{array}
\right)
$$
where $g_{\mu\nu}$ corresponds to the ordinary four dimensional metric and $g_{\mu 5}$ is the ordinary four dimensional Maxwell gauge field, $g_{55}$ is the dilaton field.
As there is one dilaton for one extra dimension, I naively would expect that the zero mass states of closed string theory, which can be written as
$$
\sum\limits_{I.J} R_{I.J} a_1^{I\dagger} \bar{a}_1^{I\dagger} ¦p^{+},\vec{p}_T \rangle
$$
and the square matrix $R_{I.J}$ can be separated into a symmetric traceless part corresponding to the graviton field, an antisymmetric part corresponding to a generalized Maxwell gauge field, and the trace which corresponds to the dilaton field.
Why is there only one dilaton field given by the trace of $R_{I.J}$, instead of $22$ dilaton fields corresponding to $22$ extra dimensions of closed string theory which has critical dimension $D = 26$? For example, why are there not $22$ dilaton fields needed to parameterize the shape of the 22 extra dimensions if they are compactified?
Bug:
In the preview, all of the math compiles apart from the fact that the array is displayed as a single column instead of a 2x2 matrix.
When posting the question, all of the maths get scrampled up.
Howver, looking at the edit history by applying this plug-in
http://www.question2answer.org/qa/17583/edit-history-plugin-improvements-bugs
all the maths works including the matrix.
What can be done about this bug?
