Let G be a simple undirected graph.
I found some examples of connected graphs G with line graphs containing no hamilton cycle, but none of them was $2$-connected.
- Are there $2$-connected graphs with a line graph containing no hamilton-cycle ?
- If yes, what is the smallest ? (Due to my search, it should have more than $7$ vertices)
Here is a counterexample on (incidentally) 8 vertices. I guess this can be generalized.
The idea is to only look for $2$-connected non-hamiltonian graphs since the line graph of a hamiltonian graph is always hamiltonian.
A natural question now is whether one can find a different kind of such graphs (not Theta graphs)