arXiv subjects

Frederic Bruno Campana

Publications and source records attributed to Frederic Bruno Campana.

3 recordsLinked to original sources

arXiv2026

Bogomolov decomposition and compact K{ä}hler manifolds of algebraic dimension zero

We prove conditionally that compact K\''ahler manifolds of algebraic dimension zero are (essentially) isogeneous to products of Kummer and `simple' ones, the latter being conjecturally bimeromorphically symplectic. `Simple' means: its general point is not contained in a nontrivial subvariety. We also prove that four-dimensional `strictly simple' manifolds are either étale quotients of tori or holomorphically symplectic. `Strictly simple' means: its only subvarieties are points and itself.

math.AG↗

arXiv2023

Kodaira additivity, birational isotriviality and specialness

We show, using [14], that a smooth projective fibration f : X $\rightarrow$ Y between connected complex quasi-projective manifolds satisfies the equality $κ$(X) = $κ$(X y) + $κ$(Y) of Logarithmic Kodaira dimensions if its fibres X y admit a good minimal model. Without the last assumption, this was conjectured in [11]. Several cases are established in [13], which inspired the present text. Although the present results overlap with those of [13] in the projective case, the approach here is different, based on the r{ô}le played by birationally isotrivial fibrations, special manifolds and the core map of Y introduced and constructed in [3].

math.AG↗

arXiv2023

Numerical and kodaira dimensions of cotangent bundles

We conjecture the equality of the numerical and Kodaira dimensions $ν_1^*(X)$ and $κ_1^*(X)$ for the cotangent bundle of compact Kähler manifolds $X$, generalising the classical case of the canonical bundle. We show or reduce it to the classical case of the canonical bundle for some peculiar manifolds: among them, the rationally connected ones, or resolutions of varieties with klt singularities and trivial first Chern class, in which case we show that $ν_1^*(X)=κ_1^*(X)=q'(X)-dim(X)$, where $q'(X)$ is the maximal irregularity of a finite étale cover of $X$. The proof rests on the Beauville-Bogomolov decomposition, and a direct computation for smooth models of quotients $A/G$ of complex tori by finite groups. We conjecture that these equalities hold true, much more generally, when $X$ is `special'. The invariant $κ_1^*$ was already introduced and studied by Fumio Sakai in [43], the particular case of the preceding conjecture when $κ_1^*(X)=-dim(X)$ was introduced and studied in [29].

math.AG↗