Geometry of solutions to the c-projective metrizability equation

TL;DR

This paper explores the geometric structures arising from solutions to the c-projectively invariant metrizability equation on almost complex manifolds, revealing a stratification of the manifold and generalizing known models.

Contribution

It introduces a broader class of solutions with non-vanishing scalar curvature and analyzes their induced geometries, extending the understanding of c-projective structures.

Findings

Manifold stratification based on solution signatures

Existence of quasi-Kähler metrics with singularities at boundary strata

Generalization of Lie group orbit decompositions in complex projective space

Abstract

On an almost complex manifold, a quasi-K\"{a}hler metric, with canonical connection in the c-projective class of a given minimal complex connection, is equivalent to a non-degenerate solution of the c-projectively invariant metrizability equation. For this overdetermined equation, replacing this maximal rank condition on solutions with a nondegeneracy condition on the prolonged system yields a strictly wider class of solutions with non-vanishing (generalized) scalar curvature. We study the geometries induced by this class of solutions. For each solution, the strict point-wise signature partitions the underlying manifold into strata, in a manner that generalizes the model, a certain Lie group orbit decomposition of $\mathbb{CP}^m$. We describe the smooth nature and geometric structure of each strata component, generalizing the geometries of the embedded orbits in the model. This includes a quasi-K\"{a}hler metric on the open strata components that becomes singular at the strata boundary. The closed strata inherit almost CR-structures and can be viewed as a c-projective infinity for the given quasi-K\"{a}hler metric.