Stein degree of proper morphisms

Fuente: arXiv
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Main Author: Birkar, Caucher
Format: Preprint
Published: 2026
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author Birkar, Caucher
author_facet Birkar, Caucher
contents The notion of degree begins in field theory as the dimension of a field extension. In algebraic geometry, this idea reappears as the degree of a finite morphism, defined using the induced extension of function fields. For proper morphisms that are not necessarily finite, Stein factorization isolates the finite part of the map and leads to the notion of Stein degree. This invariant is especially useful in birational geometry, where it interacts naturally with singularities of pairs and the study of log Calabi-Yau fibrations. In this article we give an expository introduction to these ideas, discuss motivating examples, and explain a boundedness problem for Stein degree arising in recent work of the author and collaborators.
format Preprint
id arxiv_https___arxiv_org_abs_2603_23939
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Stein degree of proper morphisms
Birkar, Caucher
Algebraic Geometry
The notion of degree begins in field theory as the dimension of a field extension. In algebraic geometry, this idea reappears as the degree of a finite morphism, defined using the induced extension of function fields. For proper morphisms that are not necessarily finite, Stein factorization isolates the finite part of the map and leads to the notion of Stein degree. This invariant is especially useful in birational geometry, where it interacts naturally with singularities of pairs and the study of log Calabi-Yau fibrations. In this article we give an expository introduction to these ideas, discuss motivating examples, and explain a boundedness problem for Stein degree arising in recent work of the author and collaborators.
title Stein degree of proper morphisms
topic Algebraic Geometry
url https://arxiv.org/abs/2603.23939