East Asian mathematical journal

The Youngnam Mathematical Society (영남수학회)
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SEMI-INVARIANT SUBMANIFOLDS OF CODIMENSION 3 IN A COMPLEX SPACE FORM WITH 𝜉-PARALLEL STRUCTURE JACOBI OPERATOR

  • U-Hang KI (The National Academy of Sciences) ;
  • Hyunjung SONG (Department of Mathematics Hankuk University of Foreign Studies)
  • Received : 2023.09.25
  • Accepted : 2023.11.29
  • Published : 2024.01.31
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Abstract

Let M be a semi-invariant submanifold of codimension 3 with almost contact metric structure (𝜙, 𝜉, 𝜂, g) in a complex space form Mn+1(c). We denote by A, K and L the second fundamental forms with respect to the unit normal vector C, D and E respectively, where C is the distinguished normal vector, and by R𝜉 = R(𝜉, ·)𝜉 the structure Jacobi operator. Suppose that the third fundamental form t satisfies dt(X, Y) = 2𝜃g(𝜙X, Y) for a scalar 𝜃(≠ 2c) and any vector fields X and Y , and at the same time R𝜉K = KR𝜉 and ∇𝜙∇𝜉𝜉R𝜉 = 0. In this paper, we prove that if it satisfies ∇𝜉R𝜉 = 0 on M, then M is a real hypersurface of type (A) in Mn(c) provided that the scalar curvature $\bar{r}$ of M holds $\bar{r}-2(n-1)c{\leq}0$.

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References

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