English

The valuative tree is the projective limit of Eggers-Wall trees

Algebraic Geometry 2019-10-03 v1

Abstract

Consider a germ CC of reduced curve on a smooth germ SS of complex analytic surface. Assume that CC contains a smooth branch LL. Using the Newton-Puiseux series of CC relative to any coordinate system (x,y)(x,y) on SS such that LL is the yy-axis, one may define the {\em Eggers-Wall tree} ΘL(C)\Theta_L(C) of CC relative to LL. Its ends are labeled by the branches of CC and it is endowed with three natural functions measuring the characteristic exponents of the previous Newton-Puiseux series, their denominators and contact orders. The main objective of this paper is to embed canonically ΘL(C)\Theta_L(C) into Favre and Jonsson's valuative tree P(V)\mathbb{P}(\mathcal{V}) of real-valued semivaluations of SS up to scalar multiplication, and to show that this embedding identifies the three natural functions on ΘL(C)\Theta_L(C) as pullbacks of other naturally defined functions on P(V)\mathbb{P}(\mathcal{V}). As a consequence, we prove an inversion theorem generalizing the well-known Abhyankar-Zariski inversion theorem concerning one branch: if LL' is a second smooth branch of CC, then the valuative embeddings of the Eggers-Wall trees ΘL(C)\Theta_{L'}(C) and ΘL(C)\Theta_L(C) identify them canonically, their associated triples of functions being easily expressible in terms of each other. We prove also that the space P(V)\mathbb{P}(\mathcal{V}) is the projective limit of Eggers-Wall trees over all choices of curves CC. As a supplementary result, we explain how to pass from ΘL(C)\Theta_L(C) to an associated splice diagram.

Keywords

Cite

@article{arxiv.1807.02841,
  title  = {The valuative tree is the projective limit of Eggers-Wall trees},
  author = {Evelia R. García Barroso and Pedro D. González Pérez and Patrick Popescu-Pampu},
  journal= {arXiv preprint arXiv:1807.02841},
  year   = {2019}
}

Comments

45 pages, 20 figures