A Note on Generalized Recurrent Riemannian Manifold
A Note on Rakić Duality Principle for Osserman Manifolds
A note on smooth toral reductions of spheres.
A note on the volume of -Einstein manifolds with skew-torsion
We study the volume of compact Riemannian manifolds which are Einstein with respect to a metric connection with (parallel) skew-torsion. We provide a result for the sign of the first variation of the volume in terms of the corresponding scalar curvature. This generalizes a result of M. Ville [Vil] related with the first variation of the volume on a compact Einstein manifold.
A note on -conformally flat contact manifolds.
A property of Wallach's flag manifolds
In this note we study the Ledger conditions on the families of flag manifold , , constructed by N. R. Wallach in (Wallach, N. R., Compact homogeneous Riemannian manifols with strictly positive curvature, Ann. of Math. 96 (1972), 276–293.). In both cases, we conclude that every member of the both families of Riemannian flag manifolds is a D’Atri space if and only if it is naturally reductive. Therefore, we finish the study of made by D’Atri and Nickerson in (D’Atri, J. E., Nickerson, H. K., Geodesic...
A remark on four-dimensional almost Kähler-Einstein manifolds with negative scalar curvature.
A short note on -biharmonic hypersurfaces
In the present paper we give some properties of -biharmonic hypersurfaces in real space forms. By using the -biharmonic equation for a hypersurface of a Riemannian manifold, we characterize the -biharmonicity of constant mean curvature and totally umbilical hypersurfaces in a Riemannian manifold and, in particular, in a real space form. As an example, we consider -biharmonic vertical cylinders in .
A spectral estimate for the Dirac operator on Riemannian flows
We give a new upper bound for the smallest eigenvalues of the Dirac operator on a Riemannian flow carrying transversal Killing spinors. We derive an estimate on both Sasakian and 3-dimensional manifolds, and partially classify those satisfying the limiting case. Finally, we compare our estimate with a lower bound in terms of a natural tensor depending on the eigenspinor.
A Study on -recurrence -curvature tensor in -contact metric manifolds
In this paper we study -recurrence -curvature tensor in-contact metric manifolds.
Abelian analytic torsion and symplectic volume
This article studies the abelian analytic torsion on a closed, oriented, Sasakian three-manifold and identifies this quantity as a specific multiple of the natural unit symplectic volume form on the moduli space of flat abelian connections. This identification computes the analytic torsion explicitly in terms of Seifert data.
Affin manifolds with nilpotent holonomy.
Almost contact metric 3-submersions.
Almost hyper-Hermitian structures in bundle spaces over manifolds with almost contact -structure
We consider almost hyper-Hermitian structures on principal fibre bundles with one-dimensional fiber over manifolds with almost contact 3-structure and study relations between the respective structures on the total space and the base. This construction suggests the definition of a new class of almost contact 3-structure, which we called trans-Sasakian, closely connected with locally conformal quaternionic Kähler manifolds. Finally we give a family of examples of hypercomplex manifolds which are not...
Almost-Bieberbach groups with prime order holonomy
The main issue of this paper is an attempt to find a decomposition theorem for infra-nilmanifolds in the same spirit as a result of A. Vasquez for flat Riemannian manifolds. That is: we look for infra-nilmanifolds with prime order holonomy which can be obtained as a fiber space with a non-trivial nilmanifold as fiber and an infra-nilmanifold as its base. In this perspective, we prove the following algebraic result: if E is an almost-Bieberbach group with prime order holonomy,...
A-manifolds on a principal torus bundle over an almost Hodge A-manifold base
An A-manifold is a manifold whose Ricci tensor is cyclic-parallel, equivalently it satisfies ∇XXRic(X,X) = 0. This condition generalizes the Einstein condition. We construct new examples of A-manifolds on r-torus bundles over a base which is a product of almost Hodge A-manifolds
An example of Lie group with Sasakian structure of constant -sectional curvature.
An explicit classification of 3-dimensional Riemannian spaces satisfying
An improved Chen-Ricci inequality for special slant submanifolds in Kenmotsu space forms
B. Y. Chen [Arch. Math. (Basel) 74 (2000), 154-160] proved a geometrical inequality for Lagrangian submanifolds in complex space forms in terms of the Ricci curvature and the squared mean curvature. Recently, this Chen-Ricci inequality was improved in [Int. Electron. J. Geom. 2 (2009), 39-45]. On the other hand, K. Arslan et al. [Int. J. Math. Math. Sci. 29 (2002), 719-726] established a Chen-Ricci inequality for submanifolds, in particular in contact slant submanifolds, in Kenmotsu...
An integral formula for non-Codazzi tensors