\documentclass[DIV12,11pt]{scrartcl}

%%%%%%%%%%%%%%
% please leave this unchanged ...

\usepackage{amsthm,amssymb,amsmath}
\usepackage[noblocks]{authblk}

\renewcommand\Affilfont{\small}

\setkomafont{title}{\normalfont \LARGE \bfseries}
\setkomafont{section}{\normalfont \Large \bfseries \boldmath}
\setkomafont{subsection}{\normalfont \large \bfseries}
\setkomafont{subsubsection}{\normalfont \normalsize \bfseries}
\setkomafont{descriptionlabel}{\itshape}
\setkomafont{paragraph}{\normalfont \bfseries \boldmath}

\newtheorem{theorem}{Theorem}
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{corollary}[theorem]{Corollary}
\newtheorem{remark}[theorem]{Remark}
\newtheorem{claim}[theorem]{Claim}
\newtheorem{definition}[theorem]{Definition}
\newtheorem{proposition}[theorem]{Proposition}

\pagestyle{empty}

% ... until here
%%%%%%%%%%%%%%

%%%%%%%%%%%%%%
% below you can load other packages, define commands, ...


%%%%%%%%%%%%%%
% edit appropriately
\title{My Title}

\author[1]{Anne First}
\author[2]{Bill Second}
\author[1,2]{Christine Third}
\author[3]{David Fourth}

\affil[1]{First University}
\affil[2]{Second University}
\affil[3]{Third University}

\date{\vspace*{-2em}}

%%%%%%%%%%%%%%

\begin{document}

\maketitle

\thispagestyle{empty}

\begin{abstract}
My abstract if I want one.
\end{abstract}

\section{My First Section}

Blah, blah, blah\ldots

\end{document}
