geometry-topology / Birational geometry, Kodaira dimension of smooth families

Popa's logarithmic additivity conjecture for log-smooth families

Theorem 1.1: under Popa's hypotheses (reduced SNC EE, DD, support inclusion, stratum smoothness over VV), κ(X,KX+E)≤κ(Y,KY+D)+κ(F,KF+EF)\kappa(X,K_X+E)\le\kappa(Y,K_Y+D)+\kappa(F,K_F+E_F), and if either term on the right is −∞-\infty every H0(X,m(KX+E))H^0(X,m(K_X+E)) vanishes; no abundance or good-model hypothesis. With the family's logarithmic subadditivity this gives equality, Corollary 1.2. Either divisor may be zero, which covers additivity for smooth projective morphisms; the paper itself claims only Conjecture 3.9. Not covered: families that are not log-smooth over the open base.

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geometry-topologySep 26, 2026Significance 35/100Registry: unreviewed

Popa's logarithmic additivity conjecture for log-smooth families

Prior state unknown→proved

Theorem 1.1: under Popa's hypotheses (reduced SNC EE, DD, support inclusion, stratum smoothness over VV), κ(X,KX+E)≤κ(Y,KY+D)+κ(F,KF+EF)\kappa(X,K_X+E)\le\kappa(Y,K_Y+D)+\kappa(F,K_F+E_F), and if either term on the right is −∞-\infty every H0(X,m(KX+E))H^0(X,m(K_X+E)) vanishes; no abundance or good-model hypothesis. With the family's logarithmic subadditivity this gives equality, Corollary 1.2. Either divisor may be zero, which covers additivity for s…

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Theorem 1.1: under Popa's hypotheses (reduced SNC EE, DD, support inclusion, stratum smoothness over VV), κ(X,KX+E)≤κ(Y,KY+D)+κ(F,KF+EF)\kappa(X,K_X+E)\le\kappa(Y,K_Y+D)+\kappa(F,K_F+E_F), and if either term on the right is −∞-\infty every H0(X,m(KX+E))H^0(X,m(K_X+E)) vanishes; no abundance or good-model hypothesis. With the family's logarithmic subadditivity this gives equality, Corollary 1.2. Either divisor may be zero, which covers additivity for smooth projective morphisms; the paper itself claims only Conjecture 3.9. Not covered: families that are not log-smooth over the open base.

Theorem 1.1: under Popa's hypotheses (reduced SNC EE, DD, support inclusion, stratum smoothness over VV), κ(X,KX+E)≤κ(Y,KY+D)+κ(F,KF+EF)\kappa(X,K_X+E)\le\kappa(Y,K_Y+D)+\kappa(F,K_F+E_F), and if either term on the right is −∞-\infty every H0(X,m(KX+E))H^0(X,m(K_X+E)) vanishes; no abundance or good-model hypothesis. With the family's logarithmic subadditivity this gives equality, Corollary 1.2. Either divisor may be zero, which covers additivity for smooth projective morphisms; the paper itself claims only Conjecture 3.9. Not covered: families that are not log-smooth over the open base.

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Popa's logarithmic additivity conjecture for log-smooth families — Mathematical Frontier Network