Equations going outside margin. Springer LNCS format

Question

The equation, I am using is going outside the margin in Springer LNCS format. The MWE is shown below.

\documentclass[runningheads]{llncs}
\usepackage{amsmath,amssymb}
\usepackage{mathtools, nccmath}
\begin{document}
        \begin{align}
        L_{B_{1} A_{1}} L_{B_{0} A_{0}}\left(\left|I_{1}\right\rangle\right) & =L_{B_{1} A_{1}} L_{B_{0} A_{0}}\left(\frac{1}{2^{m}} \sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}\left|P_{b a}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle\right)\\
        & =\frac{1}{2^{m}}\left(\underset{b a \neq B_{0} A_{0}, B_{1} A_{1}}{\displaystyle\sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}}\left|P_{ba}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle+U_{B A}\left(\left|P_{B_{0} A_{0}}\right|\right)\left|B_{0} A_{0}\right\rangle+U_{B A}\left(\left|P_{B_{1} A_{1}}\right\rangle\right)\left|B_{1} A_{1}\right\rangle\right) \\
        & =\frac{1}{2^{m}}
        \left(\begin{array}{rl}
            \underset{b a \neq B_{0} A_{0}, B_{1} A_{1}}{\displaystyle\sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}}\left|P_{b a}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle &+\left|p_{B_{0} A_{0}}^{2} p_{B_{0} A_{0}}^{3^{\prime}} \cdots p_{B_{0} A_{0}}^{0^{\prime}} p_{B_{0} A_{0}}^{1^{\prime}}\right\rangle\left|B_{0} A_{0}\right\rangle \\
            &+\left|p_{B_{1} A_{1}}^{2^{\prime}} p_{B_{1} A_{1}}^{3^{\prime}} \cdots p_{B_{1} A_{1}}^{0^{\prime}} p_{B_{1} A_{1}}^{1^{\prime}}\right\rangle\left|B_{1} A_{1}\right\rangle
        \end{array}\right)
    \end{align}
\end{document}

Let the imaginary yellow line is the boarder. You can see that the equation crosses this margin. Whenever I am trying, it is showing errors. Somebody please help me to correct it.

Does this answer your question? How can I split an equation over two (or more) lines — KersouMan, Sep 03 '21 at 06:38
You could also look at the answers to this question or this question — KersouMan, Sep 03 '21 at 06:44
unrelated but no need to use 2^{\prime} as 2' produces identical output. — David Carlisle, Sep 03 '21 at 07:42

score 1 · Accepted Answer · answered Sep 03 '21 at 09:15

I propose to use the fleqn environment, since you load nccmath, and aligned environments. Note you don't have to load amsmath, since both amsmath and nccmath load it.

\documentclass[runningheads]{llncs}
\usepackage{amssymb}
\usepackage{nccmath, mathtools}
\begin{document}
\begin{fleqn}
        \begin{align}
        & L_{B_{1} A_{1}} L_{B_{0} A_{0}}\left(\left|I_{1}\right\rangle\right) =L_{B_{1} A_{1}} L_{B_{0} A_{0}}\left(\frac{1}{2^{m}} \sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}\left|P_{b a}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle\right)\
        & =\frac{1}{2^{m}}\Biggl(\underset{b a \neq B_{0} A_{0}, B_{1} A_{1}}{\displaystyle\sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}}\left|P_{ba}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle \begin{aligned}[t] & +U_{B A}\left(\left|P_{B_{0} A_{0}}\right|\right)\left|B_{0} A_{0}\right\rangle\
         & +U_{B A}\left(\left|P_{B_{1} A_{1}}\right\rangle\right)\left|B_{1} A_{1}\right\rangle\Biggr)
        \end{aligned}\
        & =\frac{1}{2^{m}}
        \Biggl( \underset{b a \neq B_{0} A_{0}, B_{1} A_{1}}{\sum_{b=0}^{2^{m}-1} \sum_{a=0}^{2^{m}-1}}\hspace*{-0.5em}\left|P_{b a}\right\rangle\left|b^{\prime}\right\rangle\left|a^{\prime}\right\rangle
        \begin{aligned}[t] &+\left|p_{B_{0} A_{0}}^{2} p_{B_{0} A_{0}}^{3^{\prime}} \cdots p_{B_{0} A_{0}}^{0^{\prime}} p_{B_{0} A_{0}}^{1^{\prime}}\right\rangle\left|B_{0} A_{0}\right\rangle \
            &+\left|p_{B_{1} A_{1}}^{2^{\prime}} p_{B_{1} A_{1}}^{3^{\prime}} \cdots p_{B_{1} A_{1}}^{0^{\prime}} p_{B_{1} A_{1}}^{1^{\prime}}\right\rangle\left|B_{1} A_{1}\right\rangle\Biggr)
        \end{aligned}
    \end{align}
\end{fleqn}
\end{document}

Equations going outside margin. Springer LNCS format

1 Answers1