English

Componentwise height bounds for polynomial value-set lifting

Number Theory 2026-05-14 v1 Algebraic Geometry

Abstract

Let f,gk[x]f,g \in k[x] be nonconstant polynomials over a number field kk. We count SS-integer inputs aa for which f(a)f(a) has a kk-rational preimage under gg, after removing the polynomial graph components Y=h(X)Y=h(X) with f=ghf=g\circ h. The main theorem gives componentwise height bounds. For a rational component of f(X)g(Y)=0f(X)-g(Y)=0 with one geometric point at infinity and projection degree dX(C)d_X(C) to the XX-line, the corresponding contribution has the sharp power-log order B[k:Q]/dX(C)(logB)qk,SB^{[k:\mathbb{Q}]/d_X(C)}(\log B)^{q_{k,S}}, where qk,S=rkOk,S=S1q_{k,S}=\mathrm{rk}\,\mathcal{O}_{k,S}^{\ast}=|S|-1, precisely when its XX-parametrization is SS-active. Rational components with two geometric points at infinity contribute only polylogarithmically, and all other components contribute finitely many inputs. Over Q\mathbb{Q}, square-root growth after graph removal occurs exactly from active rational components with one geometric point at infinity and dX(C)=2d_X(C)=2. We give an explicit thin exceptional set for the generic multiplicity theorem and prove that every square-root source forces gg to have an involutive affine symmetry.

Keywords

Cite

@article{arxiv.2605.12903,
  title  = {Componentwise height bounds for polynomial value-set lifting},
  author = {Henry Shin},
  journal= {arXiv preprint arXiv:2605.12903},
  year   = {2026}
}

Comments

27 pages; comments welcome