# partial lines above and below an equation in a multicols-environment

First of all I am a bit surprised to find a greater distance above the equation than below it. But that is not my question, just a remark.

My main point is that I want to have a horizontal line at the bottom of the upper left column and likewise a horizontal line at the top of the lower right column, i.e. directly above the equation on the left side and below the equation on the right side.

I saw this in the Physical Review Letters and I thought whether this is possible (with reasonable effort) with LaTeX. Do you have any idea how to realize it?

I am sorry but I can't upload a graph on this computer, but I will try it later, if required.

\documentclass{scrartcl}
\usepackage{multicol}
\usepackage{blindtext}
\begin{document}
\begin{multicols}{2}
\blindtext
\end{multicols}

$$E = m c^2$$

\begin{multicols}{2}
\blindtext
\end{multicols}
\end{document}

• If you start a paragraph with display math (by leaving a blank line above it, or ending or starting multicols above it, tex will always do the wrong thing. – David Carlisle Aug 15 '16 at 13:31
• Ack. I do not have problems with inserting something like \vspace{-\baselineskip} to correct the distance. – Jürgen Aug 15 '16 at 13:38
• @Jürgen But you shouldn't need to insert such commands of you play nicely with latex. – samcarter_is_at_topanswers.xyz Aug 15 '16 at 14:04
• PRL uses journals.aps.org/revtex, maybe just have a look how they do it? – samcarter_is_at_topanswers.xyz Aug 15 '16 at 14:06
• Well, sounds like a pretty good idea. I had a look at the 7500+ lines of revtex4-1.cls and must admit that I have not the faintest clue where this miracle might be. Even a look into the docs does not really help me. Sigh! – Jürgen Aug 15 '16 at 14:25

There is an automatic \par before and after the multicol, so the blank lines have no effect. Note: \multicolsep is the space added before and after multicol.

\documentclass{scrartcl}
\usepackage{multicol}
\usepackage{blindtext}

\newcommand{\abovedisplayline}{\vspace{-\multicolsep}\noindent
\rlap{\rule[.6\baselineskip]{\dimexpr 0.5\textwidth-0.5\columnsep}{.5pt}}}

\newcommand{\belowdisplayline}{\hspace{\textwidth}%
\llap{\rule{\dimexpr 0.5\textwidth-0.5\columnsep}{.5pt}}%
\vspace{-0.2\baselineskip}\par\vspace{-\multicolsep}}

\begin{document}
\begin{multicols}{2}
\blindtext
\global\columnwidth=\columnwidth
\end{multicols}

\abovedisplayline
$$E = m c^2$$
\belowdisplayline

\begin{multicols}{2}
\blindtext
\end{multicols}
\end{document}


Modified solution to match tikz version.

\newcommand{\abovedisplayline}{\vspace{-\multicolsep}\noindent
\rlap{\rule[.6\baselineskip]{0.5\textwidth}{.7pt}\smash{\rule[.6\baselineskip]{.7pt}{.5\baselineskip}}}}

\newcommand{\belowdisplayline}{\hspace{\textwidth}%
\llap{\smash{\rule[\dimexpr 0.7pt-.5\baselineskip]{0.7pt}{.5\baselineskip}}%
\rule{0.5\textwidth}{.7pt}}%
\vspace{-0.2\baselineskip}\par\vspace{-\multicolsep}}

• Oh, this easy? Thanks a lot for your help. – Jürgen Aug 16 '16 at 6:25

Just to close this topic.

I modified John's answer (thanks!) to my taste and it finally looks like this:

Admittedly it is a bit over the top to use tikz at this point, but I am using it a lot in the rest of the text and I am far more fluent with it than with other measures.

\documentclass{scrartcl}
\usepackage{multicol}
\usepackage{blindtext}
\usepackage{tikz}

\newcommand{\abovedisplayline}{\vspace{-\multicolsep}\noindent
\rlap{\raisebox{.6\baselineskip}{\tikz{\begin{pgfinterruptboundingbox}\draw[line width=0.7pt] (0,0) -| (0.5\textwidth,6pt);\end{pgfinterruptboundingbox}}}}}

\newcommand{\belowdisplayline}{\hspace{\textwidth}%
\llap{\tikz{\begin{pgfinterruptboundingbox}\draw[line width=0.7pt] (-0.5\textwidth,-6pt) |- (0,0);\end{pgfinterruptboundingbox}}}%
\vspace{-0.2\baselineskip}\par\vspace{-\multicolsep}}

\begin{document}
\begin{multicols}{2}
\blindtext
\global\columnwidth=\columnwidth
\end{multicols}

\abovedisplayline
$$E = m c^2$$
\belowdisplayline

\begin{multicols}{2}
\blindtext
\end{multicols}
\end{docum