A Generalized RSK for Enumerating Linear Series on $n$-pointed Curves
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arXiv
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| Format: | Preprint |
| Veröffentlicht: |
2022
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| author | Gillespie, Maria Reimer-Berg, Andrew |
| author_facet | Gillespie, Maria Reimer-Berg, Andrew |
| contents | We give a combinatorial proof of a recent geometric result of Farkas and Lian on linear series on curves with prescribed incidence conditions. The result states that the expected number of degree-$d$ morphisms from a general genus $g$, $n$-marked curve $C$ to $\mathbb{P}^r$, sending the marked points on $C$ to specified general points in $\mathbb{P}^r$, is equal to $(r+1)^g$ for sufficiently large $d$. This computation may be rephrased as an intersection problem on Grassmannians, which has a natural combinatorial interpretation in terms of Young tableaux by the classical Littlewood-Richardson rule. We give a bijection, generalizing the well-known RSK correspondence, between the tableaux in question and the $(r+1)$-ary sequences of length $g$, and we explore our bijection's combinatorial properties.
We also apply similar methods to give a combinatorial interpretation and proof of the fact that, in the modified setting in which $r=1$ and several marked points map to the same point in $\mathbb{P}^1$, the number of morphisms is still $2^g$ for sufficiently large $d$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2201_00416 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | A Generalized RSK for Enumerating Linear Series on $n$-pointed Curves Gillespie, Maria Reimer-Berg, Andrew Combinatorics Algebraic Geometry 05E14 (Primary) 05A05, 14N10 (Secondary) We give a combinatorial proof of a recent geometric result of Farkas and Lian on linear series on curves with prescribed incidence conditions. The result states that the expected number of degree-$d$ morphisms from a general genus $g$, $n$-marked curve $C$ to $\mathbb{P}^r$, sending the marked points on $C$ to specified general points in $\mathbb{P}^r$, is equal to $(r+1)^g$ for sufficiently large $d$. This computation may be rephrased as an intersection problem on Grassmannians, which has a natural combinatorial interpretation in terms of Young tableaux by the classical Littlewood-Richardson rule. We give a bijection, generalizing the well-known RSK correspondence, between the tableaux in question and the $(r+1)$-ary sequences of length $g$, and we explore our bijection's combinatorial properties. We also apply similar methods to give a combinatorial interpretation and proof of the fact that, in the modified setting in which $r=1$ and several marked points map to the same point in $\mathbb{P}^1$, the number of morphisms is still $2^g$ for sufficiently large $d$. |
| title | A Generalized RSK for Enumerating Linear Series on $n$-pointed Curves |
| topic | Combinatorics Algebraic Geometry 05E14 (Primary) 05A05, 14N10 (Secondary) |
| url | https://arxiv.org/abs/2201.00416 |