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The Ample Cone of the Kontsevich Moduli Space

Published online by Cambridge University Press:  20 November 2018

Izzet Coskun
Affiliation:
Department of Mathematics, Statistics and Computer Science, University of Illinois at Chicago, Chicago, IL 69607, [email protected]
Joe Harris
Affiliation:
Department of Mathematics, Stony Brook University, Stony Brook, NY 11794, [email protected]
Jason Starr
Affiliation:
Department of Mathematics, Harvard University, Cambridge, MA 02138, [email protected]
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Abstract

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We produce ample (resp. NEF, eventually free) divisors in the Kontsevich space ${{\overline{\mathcal{M}}}_{\text{0,}n}}\left( {{\mathbb{P}}^{r}},d \right)$ of $n$-pointed, genus 0, stable maps to ${{\mathbb{P}}^{r}}$, given such divisors in ${{\overline{\mathcal{M}}}_{\text{0,}n+d}}$ We prove that this produces all ample (resp. NEF, eventually free) divisors in ${{\overline{\mathcal{M}}}_{\text{0,}n}}\left( {{\mathbb{P}}^{r}},\,d \right)$ As a consequence, we construct a contraction of the boundary $\,\,\mathop{\bigcup }_{k=1}^{\left\lfloor {d}/{2}\; \right\rfloor }\,{{\Delta }_{k,d-k}}$ in ${{\overline{\mathcal{M}}}_{\text{0,}0}}\left( {{\mathbb{P}}^{r}},d \right)$ analogous to a contraction of the boundary $\mathop{\bigcup }_{k=3}^{\left\lfloor {n}/{2}\; \right\rfloor }\,{{\widetilde{\Delta }}_{k,n-k}}$ in ${{\overline{\mathcal{M}}}_{\text{0,}n}}$ first constructed by Keel and McKernan.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2009

References

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