Kenmotsu pseudo-Riemannian manifolds

In this paper, we study some properties of Kenmotsu manifolds with pseudo-Riemannian metrics. We prove that this kind of manifolds satisfying certain conditions such as R(X; Y ) R = 0;R(X; Y ) S = 0 are Einstein manifolds. Also some sucient conditions for a Kenmotsu pseudo-Riemannian metric manifold to be Einstein are obtained

On Bernstein-Type Theorems in Semi-Riemannian Warped Products

Complete spacelike hypersurfaces immersed in semi-Riemannian warped products are investigated. By using a technique according to Yau (1976) and a reasonable restriction on the mean curvature of the hypersurfaces, we obtain some new Bernstein-type theorems which extend some known results proved by Camargo et al. (2011) and Colares and Lima (2012)

Nonsmoothable group actions on elliptic surfaces

Let G be a cyclic group of order 3, 5 or 7, and X=E(n) be the relatively minimal elliptic surface with rational base. In this paper, we prove that under certain conditions on n, there exists a locally linear G-action on X which is nonsmoothable with respect to infinitely many smooth structures on X. This extends the main result of our previous paper.Comment: 22 page

A CLASSIFICATION OF SOME ALMOST α-PARA-KENMOTSU MANIFOLDS

In this paper, we mainly study local structures and curvatures of the almost α-para-Kenmotsu manifolds. In particular, locally symmetric almost α-para-Kenmotsu manifolds satisfying certain nullity conditions are classified

SOME RESULTS ON (k, µ)'-ALMOST KENMOTSU MANIFOLDS

In this paper, we study the quasi-conformal curvature tensor C and projective curvature tensor P on a (k, µ)'-almost Kenmotsu manifold M^2n+1 of dimensiongreater than 3. We obtain that if M 2n+1 is non-Kenmotsu and satisfies R · C = 0 orP · P = 0, then it is locally isometric to the Riemannian product H^(n+1)(-4) × R^n