In this article, we describe the structure of codimension one foliations with canonical singularities and numerically trivial canonical class on varieties with terminal singularities, extending a result of Loray, Pereira and Touzet to this context. COFECUB project Ma932/19 and the ANR project Foliage (ANR grant Nr ANR-16-CE40-0008-01).2. Notation, conventions, and used facts 2.1. Global Convention. Throughout the paper a variety is a reduced and irreducible scheme separated and of finite type over a field.Given a scheme X, we denote by X reg its smooth locus. Suppose that k = C. We will use the notions of terminal, canonical, klt, and lc singularities for pairs without further explanation or comment and simply refer to [KM98, Section 2.3] for a discussion and for their precise definitions. We refer to [KM98] and [KMM87] for standard references concerning the minimal model program.2.2. Q-factorializations and Q-factorial terminalizations.Definition 2.1. Let X be a normal complex quasi-projective variety with klt singularities. A Q-factorialization is a small birational projective morphism β : Z → X, where Z is Q-factorial with klt singularities.Fact 2.2. The existence of Q-factorializations is established in [Kol13, Corollary 1.37]. Note that we must haveDefinition 2.3. Let X be a normal complex quasi-projective variety with canonical singularities. A Q-factorial terminalization of X is a birational crepant projective morphism β : Z → X where Z is Q-factorial with terminal singularities. Fact 2.4. The existence of Q-factorial terminalizations is established in [BCHM10, Corollary 1.4.3].2.3. Projective space bundle. If E is a locally free sheaf of finite rank on a variety X, we denote by P(E ) the variety Proj X S • E , and by O P(E ) (1) its tautological line bundle.
Stability.The word stable will always mean slope-stable with respect to a given movable curve class. Ditto for semistable and polystable. We refer to [HL97, Definition 1.2.12] for their precise definitions.