Avoid pagebreak between equation and label

Question

I have a very long equation which barely fits into one line, but the label does not and is positioned one line below. The problem is that if the equation is at the end of a page, the label is moved to the next page.

If possible, I would like to keep the equation as is (no splitting up into two lines, no decreasing the font size), but label should always be directly below the equation.

Edit to provide further information:

Trying to construct a MWE, I think I found the cause, but still no way around. The problem occurs when using the Springer svjour3 class (http://www.springeropen.com/authors/tex) in conjunction with the amsmath package. Not loading amsmath puts the label into the same line.

Unfortunately, this seems not to be an option as I need for example \DeclareMathOperator, besides amsmath is loaded by tikz anyways.

\documentclass[twocolumn]{svjour3}

\usepackage{amsmath}

\begin{document}

\title{Insert your title here}
\author{First Author}
\maketitle

\section{Section title}
\label{sec:1}
Some text. Some text. Some text. Some text. Some text. Some text.
\vspace{12cm}

\begin{equation}
a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2=c^2.
\end{equation} 

\end{document}

Answer 1

If you cramp up the horizontal spacing (to rather dangerously small values) then it fits:

\documentclass[twocolumn]{svjour3}

\usepackage{amsmath}

\begin{document}

\title{Insert your title here}
\author{First Author}
\maketitle

\section{Section title}
\label{sec:1}
Some text. Some text. Some text. Some text. Some text. Some text.
\vspace{12cm}

\begin{equation}
\medmuskip=0mu
\thickmuskip=1mu
a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2=c^2.
\end{equation} 

\end{document}

---

Alternatively if you want the same layout, but in an unbreakable unit, you can use a minipage

\noindent
\begin{minipage}{\linewidth}
\begin{equation}
a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2+a^2+b^2=c^2.
\end{equation} 
\end{minipage}