KÄhler immersions of KÄhler-Ricci solitons into definite or indefinite complex space forms

Let (g, X) be a Kähler-Ricci soliton (KRS) on a complex manifold M. We prove that if the Kähler manifold (M, g) can be Kähler immersed into a definite or indefinite complex space form then g is Einstein. Notice that there is no topological assumptions on the manifold M and the Kähler immersion is not required to be injective. Our result extends the result obtained in Bedulli and Gori [Proc. Amer. Math. Soc. 142 (2014), pp. 1777-1781] asserting that a KRS on a compact Kähler submanifold M ⊂ CPN which is a complete intersection is Kähler-Einstein (KE).