The resultant conjecture for self maps of the projective line over function fields

Let KK be a function field over a field kk, and let φ\varphi be a self map of degree dd of PK1\mathbb{P}^1_K. Let R(φ)R(\varphi) be the minimal resultant and let fcr(φ)\mathfrak{f}_{cr}(\varphi) be the critical conductor. Let pp be the characteristic of kk, and let ee be the inseparability degree of the canonical map induced by φ\varphi from Spec(K)\operatorname{Spec}(K) to the moduli space Md\mathcal{M}_d. Resultant conjecture for a function field. There exist a constant C(K)C(K) and an integer s(d)s(d) such that

deg(R(φ))pes(d)(C(K)+deg(fcr(φ))).\operatorname{deg}(R(\varphi))\leqslant p^e s(d)(C(K)+\operatorname{deg}(\mathfrak{f}_{cr}(\varphi)) ).

The conjecture concerns boundedness of the minimal resultant in terms of the critical conductor, motivated by analogous boundedness results for elliptic curves and their Lattès maps. The source gives no resolution status.

Sources & referencesView supporting material

Primary source

Lucien Szpiro, Michael Tepper and Phillip Williams, “Resultant and conductor of geometrically semi-stable self maps of the projective line over a number field or function field”, arXiv:1010.5030 (2012).

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