Abstract
Let M be a compact almost coKähler manifold. If the metric g of M is a Ricci soliton and the potential vector field is pointwise collinear with the Reeb vector field, then we prove that M is Ricci-flat and coKähler and the soliton g is steady. This generalizes a Goldberg-like conjecture for coKähler manifolds obtained by Cappelletti-Montano and Pastore, namely any compact Einstein K-almost coKähler manifold is coKähler. Without the assumption of compactness, Ricci solitons with the potential vector fields pointwise collinear with the Reeb vector fields on K-almost coKähler manifolds are also studied. Moreover, we prove that there exist no gradient Ricci solitons on proper \({(\kappa, \mu)}\)-almost coKähler manifolds.
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Wang, Y. A Generalization of the Goldberg Conjecture for CoKähler Manifolds. Mediterr. J. Math. 13, 2679–2690 (2016). https://doi.org/10.1007/s00009-015-0646-8
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DOI: https://doi.org/10.1007/s00009-015-0646-8