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A note on \(R_2\)- and \(cR_2\)-manifolds. (English) Zbl 1039.53078

Following A. Gray [Tohoku Math. J., II. Ser. 28, 601–612 (1976; Zbl 0351.53040)], an almost Hermitian manifold \((M,J,g)\) is said to be an \(R_2\)-manifold if its Riemann curvature tensor \(R\) satisfies the condition: \(R(X,Y,Z,T) = R(JX,JY,Z,T) + R(JX,Y,JZ,T) + R(JX,Y,Z,JT)\) for any vector fields \(X,Y,Z,T\) on \(M\). The authors suggests to consider the class of \(cR_2\)-manifolds as those of which the Weyl conformal curvature tensor \(W\) satisfies the condition of above. He finds necessary and sufficient conditions for a curvature type tensor to realize the above condition. He discusses certain examples of \(cR_2\)-manifolds which are not \(R_2\)-manifolds.

MSC:

53C55 Global differential geometry of Hermitian and Kählerian manifolds
53C15 General geometric structures on manifolds (almost complex, almost product structures, etc.)

Citations:

Zbl 0351.53040