In earlier work, the second author showed that a closed subset of a polynomial functor can always be defined by finitely many polynomial equations. In follow-up work on GL∞-varieties, Bik–Draisma–Eggermont–Snowden showed, among other things, that in characteristic zero every such closed subset is the image of a morphism whose domain is the product of a finite-dimensional affine variety and a polynomial functor. In this paper, we show that both results can be made algorithmic: there exists an algorithm implicitise that takes as input a morphism into a polynomial functor and outputs finitely many equations defining the closure of the image; and an algorithm parameterise that takes as input a finite set of equations defining a closed subset of a polynomial functor and outputs a morphism whose image is that closed subset.
Implicitisation and Parameterisation in Polynomial Functors / Blatter, Andreas; Draisma, Jan; Ventura, Emanuele. - In: FOUNDATIONS OF COMPUTATIONAL MATHEMATICS. - ISSN 1615-3383. - (2023). [10.1007/s10208-023-09619-6]
Implicitisation and Parameterisation in Polynomial Functors
VENTURA, EMANUELE
2023
Abstract
In earlier work, the second author showed that a closed subset of a polynomial functor can always be defined by finitely many polynomial equations. In follow-up work on GL∞-varieties, Bik–Draisma–Eggermont–Snowden showed, among other things, that in characteristic zero every such closed subset is the image of a morphism whose domain is the product of a finite-dimensional affine variety and a polynomial functor. In this paper, we show that both results can be made algorithmic: there exists an algorithm implicitise that takes as input a morphism into a polynomial functor and outputs finitely many equations defining the closure of the image; and an algorithm parameterise that takes as input a finite set of equations defining a closed subset of a polynomial functor and outputs a morphism whose image is that closed subset.File | Dimensione | Formato | |
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https://hdl.handle.net/11583/2982769