# Equation goes into the right column

I have this document:

\documentclass[a4paper,11pt, twocolumn]{article}
\begin{document}
...

\begin{aligned} f(\boldsymbol{y}|\boldsymbol{\alpha},\boldsymbol{\beta})&=\binom{m}{\boldsymbol{y}}\prod_{i=1}^{k-1}\frac{\Gamma(\alpha_i+y_i)}{\Gamma(\alpha_i)} \frac{\Gamma(\beta_i+\sum_{j=i}^ky_j)}{\Gamma(\beta_i)} \\ &\qquad{} \times \frac{\Gamma(\alpha_i+\beta_i)}{\Gamma(\alpha_i+\beta_i+\sum_{j=i}^ky_j)} \end{aligned}

\end{document}

The fact is that this equation goes into the right column even if I divide it into two lines... How can I solve this problem?

... or using a simple align, and replacing | with \mid,

\documentclass[a4paper,11pt,twocolumn]{article}
\usepackage{amsmath,bm}
\begin{document}
\hrule % just to indicate width of column
\begin{align}
f(\bm{y}&\mid\bm{\alpha},\bm{\beta})= \notag\\
&\binom{m}{\bm{y}} \prod_{i=1}^{k-1}
\frac{\Gamma(\alpha_i+y_i)}{\Gamma(\alpha_i)}
\frac{\Gamma(\beta_i+\sum_{j=i}^ky_j)}{\Gamma(\beta_i)} \notag\\
\frac{\Gamma(\alpha_i+\beta_i)}{\Gamma(\alpha_i+\beta_i+\sum_{j=i}^ky_j)}
\end{align}
\end{document}
• +1. I would replace the math-old | character with the math-rel macro \mid, though, – Mico May 10 at 16:01
• Done. :-) (changed | to \mid, and \boldsymbol to \bm) – Mico May 10 at 16:19
• Thank you very much... it seems to me that they have just changed the characters on the site: I now see these differents. They are similar to Calibri font. – Sebastiano May 10 at 16:30
• Good eye! See We are switching to system fonts on May 10, 2021 for the full announcement. – Mico May 10 at 16:32
• @Mico I have not see the link....and the advice...:-))) My eyes are very very tired...and I am here for relax. – Sebastiano May 10 at 16:33

I suggest using the multline environment instead:

\documentclass[a4paper,11pt, twocolumn]{article}
\usepackage{amsmath}

\begin{document}

\begin{multline}
f(\boldsymbol{y}\mid\boldsymbol{\alpha},\boldsymbol{\beta}) = \\
\binom{m}{\boldsymbol{y}}\prod_{i=1}^{k-1}\frac{\Gamma(\alpha_i+y_i)}{\Gamma(\alpha_i)} \frac{\Gamma(\beta_i+\sum_{j=i}^ky_j)}{\Gamma(\beta_i)} \\
\times \frac{\Gamma(\alpha_i+\beta_i)}{\Gamma(\alpha_i+\beta_i+\sum_{j=i}^ky_j)}
\end{multline}

\end{document}

• Same comment about \mid that has already been mentioned. – barbara beeton May 10 at 18:31
• @barbarabeeton: Yes, I had noticed that, but I thought it was not the main point here. I'll fix it anyway. – Bernard May 10 at 18:43