\(C\)-projective transformations and holonomy groups of normal almost contact manifolds (Q1916327)

In [J. Math. Soc. Japan 9, 195-227 (1957; Zbl 0080.37401); resp. Tôhoku Math. J., II. Ser. 9, 273-297 (1957; Zbl 0090.38604)], \textit{S. Ishihara} studied the relation between the holonomy group of a real (resp. complex) manifold endowed with an affine connection on one side and the projective (resp. \(H\)-projective) transformations preserving the Ricci tensor on the other side. Let \(M\) be a normal almost contact manifold. By using \(C\)-projective transformations on \(M\) introduced in [\textit{P. Matzeu} and \textit{V. Oproiu}, Rend. Semin. Mat., Torino 45, No. 2, 41-58 (1987; Zbl 0669.53030)], the present paper studies \(C\)-projective transformations preserving the Ricci tensor which imply some properties of the holonomy groups of special torsion-free connections of \(M\). Some examples are constructed, and the particular cases when \(M\) is either Sasakian or cosymplectic are also considered.