The functorial determination conjecture for nef integral Cartier b-divisors

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Let C\mathcal{C} be the category of pairs (X,D)(X,D) where XX is a reduced integral noetherian excellent Q\mathbb{Q}-scheme and DD is a nef integral Cartier b-divisor on XX. A morphism (Y,D′)→(X,D)(Y,D')\to(X,D) consists of a morphism f:Y→Xf:Y\to X and an isomorphism D′≅f∗DD'\cong f^*D. Let C′\mathcal{C}' be the subcategory with the same objects and only those morphisms whose underlying morphisms of schemes are regular, and let ι:C′→C\iota:\mathcal{C}'\to\mathcal{C} be the natural inclusion.

Functorial determination conjecture. There exist a covariant functor Y:C′→CY:\mathcal{C}'\to\mathcal{C} and a natural transformation F:Y→ιF:Y\to\iota such that:

  1. For each (X,D)∈C(X,D)\in\mathcal{C}, the morphism F(X,D):Y(X,D)→XF(X,D):Y(X,D)\to X is a modification that is a determination of DD.
  2. If D∈CDiv⁡RXD\in\operatorname{CDiv}_{\mathbb{R}}X, then F(X,D)F(X,D) is an isomorphism.
  3. For each morphism f:(X′,D′)→(X,D)f:(X',D')\to(X,D) in C\mathcal{C}, the square
\xymatrix@C=50pt{ Y(X',D') \ar^{Y(f)}[r] \ar^{F(X',D')}[d] & Y(X,D) \ar^{F(X,D)}[d] \\ X' \ar^{f}[r] & X }

is cartesian in C\mathcal{C}.

The conjecture is a functorial refinement of the existence of determinations for nef Cartier b-divisors, motivated by resolution of turning points. The supplied text does not state whether it has been resolved.

References

Primary source

Kiran S. Kedlaya, “Good formal structures for flat meromorphic connections, III: Irregularity and turning loci”, arXiv:1308.5259 (2019).

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