Bandyopadhyay, Dacorogna, Matveev and Troyanov Math. Z. 305 (2023), p. 25 conjectured that a closed manifold admitting a flat, non-negative definite metric of constant rank m m should be finitely covered by a fiber bundle over the m m -torus. We give a counter-example to this statement and we discuss the link between this problem and the study of transversely flat Riemannian foliations.
Brice Flamencourt (Fri,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: