Notations M Riemannian manifold. N 0 normal neighborhood of the origin in T p M. N p normal neighbourhood of p, N p = exp N 0. s p geodesic symmetry with respect to p. f Φ d Φ f = f • Φ. X Φ d Φ X. K(S) sectional curvature of M at p along the section S. D r s set of tensor fields of type (r, s). I(M) the set of all isometries on M Definition 1 (normal neighborhood) A neighborhood N p of p in M ...

In this paper we prove several new characterizations of weakly unconditionally Cauchy series in Banach spaces and in the dual space of a normed space. For a given series ζ, we consider the spaces S(ζ), Sw(ζ) and S0(ζ) of bounded sequences of real numbers (ai)i such that the series P i aixi is convergent, weakly convergent or ∗-weakly convergent, respectively. By means of these spaces we charact...

In this paper we study weakly symmetric and special weakly Ricci symmetric Lorentzian β-Kenmotsu manifolds and obtained some interesting results. 2000 Mathematics Subject Classification: 53C10, 53C15.