Tropical Approach to Nagata’s Conjecture in Positive Characteristic

Nikita Kalinin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Suppose that there exists a hypersurface with the Newton polytope Δ , which passes through a given set of subvarieties. Using tropical geometry, we associate a subset of Δ to each of these subvarieties. We prove that a weighted sum of the volumes of these subsets estimates the volume of Δ from below. As a particular application of our method we consider a planar algebraic curve C which passes through generic points p1, … , pn with prescribed multiplicities m1, … , mn. Suppose that the minimal lattice width ω(Δ) of the Newton polygon Δ of the curve C is at least max (mi). Using tropical floor diagrams (a certain degeneration of p1, … , pn on a horizontal line) we prove that area(Δ)≥12∑i=1nmi2-S,whereS=12max(∑i=1nsi2|si≤mi,∑i=1nsi≤ω(Δ)).In the case m1= m2= ⋯ = m≤ ω(Δ) this estimate becomes area(Δ)≥12(n-ω(Δ)m)m2. That rewrites as d≥(n-12-12n)m for the curves of degree d. We consider an arbitrary toric surface (i.e. arbitrary Δ) and our ground field is an infinite field of any characteristic, or a finite field large enough. The latter constraint arises because it is not a priori clear what is a collection of generic points in the case of a small finite field. We construct such collections for fields big enough, and that may be also interesting for the coding theory.

Original languageEnglish
Pages (from-to)158-179
Number of pages22
JournalDiscrete and Computational Geometry
Issue number1
StatePublished - 1 Jul 2017
Externally publishedYes


  • Floor diagrams
  • Nagata’s conjecture
  • Tropical geometry
  • m-Fold point


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