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Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/196340
Degree and birationality of multi-graded rational maps
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We give formulas and effective sharp bounds for the degree of multi-graded rational maps and provide some effective and computable criteria for birationality in terms of their algebraic and geometric properties. We also extend the Jacobian dual criterion to the multi-graded setting. Our approach is based on the study of blow-up algebras, including syzygies, of the ideal generated by the defining polynomials of the rational map. A key ingredient is a new algebra that we call the saturated special fiber ring, which turns out to be a fundamental tool to analyze the degree of a rational map. We also provide a very effective birationality criterion and a complete description of the equations of the associated Rees algebra of a particular class of plane rational maps.
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BUSÉ, Laurent, CID RUIZ, Yairon and D'ANDREA, Carlos. Degree and birationality of multi-graded rational maps. Proceedings of the London Mathematical Society. 2020. Vol. 121, num. 4, pags. 743-787. ISSN 0024-6115. [consulted: 18 of June of 2026]. Available at: https://hdl.handle.net/2445/196340