Simis' Cremona-map criterion for normal Rees algebras

Let S=K[t1,,ts]S=K[t_1,\ldots,t_s], let I=(tv1,,tvs)I=(t^{v_1},\ldots,t^{v_s}), and let F=(tv1,,tvs)F=(t^{v_1},\ldots,t^{v_s}) define the associated rational monomial map

F ⁣:Ps1\dasharrowPs1.F\colon \mathbb{P}^{s-1}\dasharrow\mathbb{P}^{s-1}.

A Cremona map is a rational map admitting an inverse rational map with source Ps1\mathbb{P}^{s-1}.

Simis' reformulation. The map FF is a Cremona map if and only if the Rees algebra S[Iz]S[Iz] is normal.

This is explicitly given as a reformulation of Simis' doubly stochastic conjecture; the supplied text provides supporting results but no resolution.

Sources & referencesView supporting material

Primary source

Maria Vaz Pinto and Rafael H. Villarreal, “Graph rings and ideals: Wolmer Vasconcelos' contributions”, arXiv:2305.06270 (2025).

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