\documentclass[a4paper,12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{amssymb, mathrsfs, amsmath, amsthm, color, enumerate} 

% environment for problem:
\theoremstyle{definition}
\newtheorem{problem}{Problem}


% environment for comments:
\newenvironment{comments}{\noindent\textit{Comments.}}{\medskip}

% environment for references:
\newenvironment{references}{
	\noindent\textit{References:}
	\begingroup
		\renewcommand{\section}[2]{}
		\begin{thebibliography}{1}
}{
		\end{thebibliography}
	\endgroup
}

% command for communicator:
\newcommand{\communicator}[1]{\noindent\textit{Communicated by} #1.\medskip}



\begin{document}

\title{Template for open problems (OPSO 2021 and 2022)}

\author{Jochen Gl\"uck, Rainer Nagel, Ivan Remizov (eds.)}

\maketitle 


\begin{center}
	Please submit your open problem(s) to Jochen Glück: \\
	
	jochen.glueck@alumni.uni-ulm.de
\end{center}


%----------------------------------------------------------------------------------------
% SAMPLE PROBLEM from a different field
% (the problems submitted should be from semigroup theory, of course):

\begin{problem}[Invariant subspace problem]
	Let $H$ be a separable Hilbert space over $\mathbb{C}$ 
	and let $T: H \to H$ be a bounded linear operator.
	
	Is there always a closed subspace $\{0\} \subsetneq V \subsetneq H$ 
	which is invariant under $T$ (in the sense that $TV \subseteq V$)?
\end{problem}

\begin{comments}
	If the communicator of the problem is not the same person who originally posed the problem,
	please mention the original author of the problem here.
	
	Comments on the history and context of the problem.
	Connections to other problems and/or fields, 
	comments on potential applications and further remarks 
	which explain the relevance of the problem.
	
	For instance: 
	If $H$ is replaced with a general Banach space, 
	the answer to the problem is negative; 
	this was shown by Enflo in 1976 \cite{InvariantSubspaceProblemEnflo1976}.
\end{comments}

\begin{references}
	\bibitem{InvariantSubspaceProblemEnflo1976}
	Per Enflo.
	\newblock {On the invariant subspace problem in Banach spaces.}
	\newblock {\em S\'emin. Maurey-Schwartz 1975-1976, Espaces Lp, 
	Appl. radonif., G\'eom. Espaces de Banach, Expos\'e XIV-XV}, 6 p., 1976.
\end{references}

% Please enter your name here:
\communicator{John Doe} 
% Here, "communicator" refers to the person he communicates the problem to us, 
% not to the person who first formulated the problem.
% If there is a specific person who is known to have first formulated the problem 
% and who does not coincide with the communicator, please acknowledge them 
% within the problem-environment or within the comments-environment.


%----------------------------------------------------------------------------------------
% ANOTHER SAMPLE PROBLEM, this time without a title:

\begin{problem}
	This is an example of a problem without a title. 
	If you would like to include a title, please include it in square brackets 
	right at the beginning of the problem environment (as in Problem~1).
	
	Setting, notation, and other things that are required to understand the problem.
	Please feel free to insert as much background as necessary (within the problem environment).
	Of course, you may also use references within the problem statement, 
	for instance like this \cite{ReferenceLabel01}.
	
	Statement of the problem.
\end{problem}

\begin{comments}
	If the communicator of the problem is not the same person who originally posed the problem,
	mentioned the original author of the problem here.
	
	Comments about the history of the problem, about related results, 
	about the relevance and context of the problem, 
	about related results and partial results that are already known, and so on.
	
	References to the literature, 
	such as \cite{ReferenceLabel01} and \cite[Theorem~2.1]{ReferenceLabel01} 
	can also be used here.
\end{comments}

\begin{references}
	% Please use a new references-environment for each problem in the file
	
    \bibitem{ReferenceLabel01}
	Author 1 and Author 2.
	\newblock {On very interesting problems.}
	\newblock \emph{Journal of examples and counterexamples}, 145(5), 144--156, 1998.
	
	\bibitem{ReferenceLabel02}
	Author.
	\newblock {On even more interesting problems.}
	\newblock \emph{Rejecta Mathematica}, 144(4), 133--157, 2001.
\end{references}

% Please enter your name here:
\communicator{John Doe} 
% Here, "communicator" refers to the person he communicates the problem to us, 
% not to the person who first formulated the problem.
% If there is a specific person who is known to have first formulated the problem 
% and who does not coincide with the communicator, please acknowledge them 
% within the problem-environment or within the comments-environment.


\end{document}
