Abstract We construct projective toric surfaces whose blow-up at a general point has a non-polyhedral pseudo-effective cone.As a consequence, we prove that the pseudo-effective cone of the Grothendieck–Knudsen moduli space \overline{M}_{0,n}of stable rational curves is not polyhedral for n\geq 10.These results hold both in characteristic 0 and in characteristic 𝑝, for all primes 𝑝.Many of these toric surfaces are related to an interesting class of arithmetic threefolds that we call arithmetic elliptic pairs of infinite order.Our analysis relies on tools of arithmetic geometry and Galois representations in the spirit of the Lang–Trotter conjecture, producing toric surfaces whose blow-up at a general point has a non-polyhedral pseudo-effective cone in characteristic 0 and in characteristic 𝑝, for an infinite set of primes 𝑝 of positive density.
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On an Equivalence of Divisors on $\overline {\text {M}}_{0,n}$ from Gromov-Witten Theory and Conformal Blocks
Abstract We consider a conjecture that identifies two types of base point free divisors on$$\overline {\text {M}}_{0,n}$$ . The first arises from Gromov-Witten theory of a Grassmannian. The second comes from first Chern classes of vector bundles associated with simple Lie algebras in type A. Here we reduce this conjecture on$$\overline {\text {M}}_{0,n}$$ to the same statement forn= 4. A reinterpretation leads to a proof of the conjecture on$$\overline {\text {M}}_{0,n}$$ for a large class, and we give sufficient conditions for the non-vanishing of these divisors.
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- PAR ID:
- 10369886
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Transformation Groups
- Volume:
- 29
- Issue:
- 2
- ISSN:
- 1083-4362
- Format(s):
- Medium: X Size: p. 561-590
- Size(s):
- p. 561-590
- Sponsoring Org:
- National Science Foundation
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