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What is missing in canonical models for proper normal algebraic surfaces?

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Smooth surfaces have finitely generated canonical rings and projective canonical models. For normal surfaces, however, the graded ring of multicanonical sections is possibly nonnoetherian, such that the corresponding homogeneous spectrum is noncompact. I construct a canonical compactification by adding finitely many non-ℚ-Gorenstein points at infinity, provided that each Weil divisor is numerically equivalent to a ℚ-Cartier divisor. Similar results hold for arbitrary Weil divisors instead of the canonical class.

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Correspondence to S. Schröer.

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Schröer, S. What is missing in canonical models for proper normal algebraic surfaces?. Abh.Math.Semin.Univ.Hambg. 71, 257–268 (2001).

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  • Irreducible Component
  • Rational Singularity
  • Algebraic Surface
  • Canonical Model
  • Cartier Divisor