The logarithmic additivity conjecture for algebraic fiber spaces

Let f ⁣:XYf\colon X\to Y be an algebraic fiber space between smooth projective varieties. Let EE be a simple normal crossing divisor on XX and DD a simple normal crossing divisor on YY such that

Supp(fD)E.\operatorname{Supp}(f^*D)\subseteq E.

Assume that ff is log-smooth over V=YDV=Y\smallsetminus D, meaning that every stratum of (X,E)(X,E), including XX, is smooth over VV via ff. Let FF be a general fiber over a point of VV, and write EFE_F for the induced divisor on FF. The logarithmic additivity conjecture. One should have

κ(X,KX+E)=κ(Y,KY+D)+κ(F,KF+EF).\kappa(X,K_X+E)=\kappa(Y,K_Y+D)+\kappa(F,K_F+E_F).

This is the logarithmic extension of the strongest projective additivity conjecture and includes weaker standard cases by specialization. It is known when the base is of log general type, while the general log-smooth case remains open.

Sources & referencesView supporting material

Primary source

Mihnea Popa, “Conjectures on the Kodaira dimension”, arXiv:2111.10900 (2022).

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