Recomm. for undergrads: yes
Posted by: Agelos
on: August 4th, 2007

\begin{problem} If $G$ is a $3$-connected finite graph, is there an assignment of lengths $\ell: E(G) \to \mathb R^+$ to the edges of $G$, such that every $\ell$-geodesic cycle is \Def[peripheral]{peripheral cycle}? \end{problem}

A cycle $C$ is \emph{$\ell$-geodesic} if for every two vertices $x,y$ on $C$ there is no $x$-$y$~path in $G$ shorter, with respect to $\ell$, than both $x$-$y$~arcs on $C$.

It is not hard to prove [GS] that for every finite graph $G$ and every assignment of edge lengths $\ell: E(G) \to \mathb R^+$ the $\ell$-geodesic cycles of $G$ generate its cycle space. Thus, a positive answer to the problem would imply a new proof of Tutte's classical theorem [T] that the peripheral cycles of a $3$-connected finite graph generate its cycle space.


*[GS] Angelos Georgakopoulos, Philipp Sprüssel: \href [Geodesic topological cycles in locally finite graphs]{}. Preprint 2007.

[T] W.T. Tutte, How to draw a graph. Proc. London Math. Soc. 13 (1963), 743–768.

* indicates original appearance(s) of problem.


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