Correct way to typeset a section producing an underful box

Question

I am writing a two-column document and I have a problem with a section which produces an underfull box. What is the correct way (or some better ways) to typeset such a section so to have a beautiful output? This can be regarded as a general question as to what someone must do in such a case.

\documentclass{article}

\usepackage[top=0.7in, bottom=1.2in, left=0.8in, right=0.8in]{geometry}
\usepackage{parskip}
\setlength{\parindent}{0cm}
\usepackage{amsmath}
\usepackage{unicode-math}
\usepackage{fontspec}
\usepackage[greek,english]{babel}
\usepackage[fontsize=8pt]{scrextend}
\usepackage{multicol}

\setmainfont[Ligatures=TeX, Extension=.otf, UprightFont=*, BoldFont=*Bold, ItalicFont=*It, BoldItalicFont=*BoldIt, Mapping=tex-text]{GFSArtemisia}
\setsansfont[Mapping=tex-text]{GFSArtemisia.otf}
\setmathfont{latinmodern-math.otf}
\setmathfont[range=\varnothing]{Asana-Math.otf}
\setmathfont[range=\int]{latinmodern-math.otf}

\begin{document}

\selectlanguage{greek}

\begin{multicols*}{2}

\section{ΑΝΤΙΣΤΡΟΦΟΣ ΜΕΤΑΣΧΗΜΑΤΙΣΜΟΣ Ζ}

\end{multicols*}

\end{document}

Answer 1

As Sean mentioned in comment, it would look much nicer if set flushed to the left (ragged right). Here are two examples. One with \raggedright and one with \RaggedRight from ragged2e The second one allows hyphenation.

% arara: lualatex

\documentclass{article}
\usepackage[top=0.7in, bottom=1.2in, left=0.8in, right=0.8in]{geometry}
\setlength{\parindent}{0cm}
\usepackage{fontspec}
\usepackage[greek,english]{babel} % load after fontspec
\setmainfont[Ligatures=TeX, Extension=.otf, UprightFont=*, BoldFont=*Bold, ItalicFont=*It, BoldItalicFont=*BoldIt, Mapping=tex-text]{GFSArtemisia}
\usepackage[fontsize=8pt]{scrextend}
\usepackage{multicol}
\usepackage{ragged2e} % for \RaggedRight
\usepackage{titlesec}
\titleformat{\section}
%{\normalfont\Large\bfseries\raggedright}{\thesection}{1em}{} % chose the one you like
{\normalfont\Large\bfseries\RaggedRight}{\thesection}{1em}{}
\usepackage{blindtext} % only for demo
\usepackage{microtype} % always recommended

\begin{document}
    \selectlanguage{greek}  
    \begin{multicols*}{2}
        \section{ΑΝΤΙΣΤΡΟΦΟΣ ΜΕΤΑΣΧΗΜΑΤΙΣΜΟΣ Ζ}
        \Blindtext
    \end{multicols*}
\end{document}

\raggedright:

\RaggedRight:

---

As mentioned by egreg, you may use \usepackage{sectsty}\allsectionsfont{\RaggedRight} instead. This will be the shortest way, in case you do not want to change other properties of your section command.

Answer 2

Since you are using scrextend package, why not use scrartcl directly?

With the KOMA-Script features, this is a one liner \addtokomafont{disposition}{\raggedright}.

Here's a full example (I also removed the parskip package, since that's an option of the scr packages, too). Also note that the optional argument in \setmainfont is after the name of the font \setmainfont{<font>}[<config>].

\documentclass[fontsize=8pt,parskip=half]{scrartcl}

\usepackage[top=0.7in, bottom=1.2in, left=0.8in, right=0.8in]{geometry}
\usepackage{amsmath}
\usepackage{unicode-math}
\usepackage{fontspec}
\usepackage[greek,english]{babel}
\usepackage{multicol}

\setmainfont{Latin Modern Roman}[Ligatures=TeX]
\setmathfont{Latin Modern Math}

\addtokomafont{disposition}{\raggedright}

\begin{document}

\selectlanguage{greek}

\begin{multicols*}{2}

\section{ΑΝΤΙΣΤΡΟΦΟΣ ΜΕΤΑΣΧΗΜΑΤΙΣΜΟΣ Ζ}

\end{multicols*}

\end{document}