[Tex/LaTex] \newline command is not working inside a displayed equation



$$\partial_t \bar{A_{ij}}= e^{-4\phi}(-(D_iD_j\alpha)^{TF}+\alpha(R_{ij}^{TF}-8\pi S_{ij}^{TF})+\alpha(K\bar{A_{ij}}-2\bar{A_{il}}\bar{A_j^l})
+\beta^k\partial_k\bar{A_{ij}} + \newline
\bar{A_{ik}}\partial_j \beta^k+\bar{A_{kj}}\partial_i \beta^k-{2 \over 3}\bar{A_{ij}}\partial_k \beta^k)$$

I am trying \newline to split the equation into the second line but it is not working.

Best Answer

I assume your document uses the beamer document class. If so, the formula suffers from several problems.

  • First and foremost, $$ ...$$ is designed for single-line displayed equations: One cannot have line breaks in such a construct. I suggest you use a multline* environment.

  • The formula has multiple instances of things like \bar{A_{ij}}. The \bar "accent" isn't long enough to span the entire formula. Write either \bar{A}_{ij} or, if the bar accent is supposed to span the entire subformula, \overline{A_{ij}}. In the code below, I've chosen the former option.

  • Your formula contains the subformula {2 \over 3}. One should not use the Plain-TeX \over directive in a LaTeX document. You should write either \frac{2}{3} or -- if you want a smaller term, with text-style fraction term appearance -- \tfrac{2}{3}. See the posting What is the difference between \over and \frac? for more information on this specific issue.

  • There's one group of parentheses that spans (nearly) the entirely formula. To give it a bit more visual prominence, I suggest you (a) use square brackets instead of round parentheses and (b) use \bigl and \bigr to increase their size a bit.

enter image description here

%\usepackage{amsmath} % is loaded automatically by "beamer" class

\partial_t \bar{A}_{ij}= e^{-4\phi}
+\alpha(R_{ij}^{TF}-8\pi S_{ij}^{TF})
+\bar{A}_{ik}\partial_j \beta^k
+\bar{A}_{kj}\partial_i \beta^k
-\tfrac{2}{3}\bar{A}_{ij}\partial_k \beta^k\bigr]

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