The functorial determination conjecture for nef integral Cartier b-divisors

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:YXf:Y\to X and an isomorphism DfDD'\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:CC\iota:\mathcal{C}'\to\mathcal{C} be the natural inclusion.

Functorial determination conjecture. There exist a covariant functor Y:CCY:\mathcal{C}'\to\mathcal{C} and a natural transformation F:YιF: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 DCDivRXD\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.

Sources & referencesView supporting material

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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