Finiteness of spectral networks and bounds on noncritical tripods for high-degree polynomial cubic differentials

Determine whether the spectral networks of polynomial cubic differentials of the form \(\varphi=P(x)\,dx^{\otimes 3}\) on \(\mathbf{P}^1\) with large degree \(d\) are finite (i.e., consist of finitely many trajectories), and, contingent on finiteness, ascertain upper bounds on the number of noncritical tripods formed by trajectories starting at intersection points that are not zeros of \(\varphi\).

Background

In the paper the authors study spectral networks associated to cubic differentials on P1\mathbf{P}^1, and obtain complete descriptions for degrees d3d\leq 3. They prove finiteness results and explicit upper bounds for critical tripods (tripods formed by three critical trajectories emanating from zeros).

However, beyond the critical case, the existence and count of tripods formed by trajectories starting at intersection points not located at zeros (noncritical tripods) depend on the global finiteness of the spectral network. The authors note that while noncritical tripods do not appear for d3d\leq 3, for larger degrees it is uncertain whether spectral networks remain finite, and consequently whether one can derive bounds on the number of such tripods.

References

Note that Corollary~\ref{cor:UpperBoundTripod} does not give any information about noncritical tripods (those that are formed by trajectories that are not starting at some zero). Such tripods do not exist for $d \leq 3$ but since it is not clear whether for large $d$ the spectral network is finite or not, it is not clear either whether we can bound the number of tripods formed by trajectories starting at arbitrary intersection points.

Spectral networks for polynomial cubic differentials  (2507.07971 - Kidwai et al., 10 Jul 2025) in Remark following Corollary \ref{cor:UpperBoundTripod}, Subsubsection 5.1.2 (Upper bounds on the number of saddle connections and critical tripods)