In this paper, we prove the rational coefficient case of the global ACC for
foliated threefolds. Specifically, we consider any lc foliated log Calabi-Yau
triple (X,F,B) of dimension 3 whose coefficients belong to a set
Γ of rational numbers satisfying the descending chain condition, and
prove that the coefficients of B belong to a finite set depending only on
Γ.
To prove our main result, we introduce the concept of generalized foliated
quadruples, which is a mixture of foliated triples and Birkar-Zhang's
generalized pairs. With this concept, we establish a canonical bundle formula
for foliations in any dimension.
As for applications, we extend Shokurov's global index conjecture in the
classical MMP to foliated triples and prove this conjecture for threefolds with
nonzero boundaries and for surfaces. Additionally, we introduce the theory of
rational polytopes for functional divisors on foliations and prove some
miscellaneous results.Comment: 22 pages. Add a paragraph on pages 3-4. Proposition 6.4 and Lemma 7.2
strengthened. Small modification of the proof of 8.1. Reference update