Existence of complements conjecture for log canonical pairs

Let dd be a positive integer, let Γ[0,1]\Gamma\subset[0,1] be a DCC set, and let (X/Zz,B)(X/Z\ni z,B) be an R\mathbb{R}-complementary pair of dimension dd whose boundary coefficients lie in Γ\Gamma. An nn-complement (X/Zz,B+)(X/Z\ni z,B^+) means that (X/Zz,B+)(X/Z\ni z,B^+) is log canonical,

nB+(n+1){B}+nB,nB^+\geq \lfloor(n+1)\{B\}\rfloor+n\lfloor B\rfloor,

and

n(KX+B+)0n(K_X+B^+)\sim 0

over a neighborhood of zz.

Existence of Complements Conjecture. There exists a positive integer nn, depending only on dd and Γ\Gamma, such that every such pair (X/Zz,B)(X/Z\ni z,B) has an nn-complement (X/Zz,B+)(X/Z\ni z,B^+). Moreover, if the closure of Γ\Gamma belongs to [0,1]Q[0,1]\cap\mathbb Q, then B+B^+ can be chosen so that B+BB^+\geq B.

Uniform complements are a key input for canonical bundle formulas and boundedness arguments. The conjecture is known in dimensions at most three, while the general case remains open.

Sources & referencesView supporting material

Primary source

Guodu Chen, Jingjun Han and Wenfei Liu, “On the Iitaka volumes of log canonical surfaces and threefolds”, arXiv:2407.07391 (2024).

Additional references

3 papers in this index state this conjecture (2020–2024). The statement above is taken from the most recent of them; the others are arXiv:2301.04813, arXiv:2002.02246.

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.