Pradip Majhi

Weakly Ricci symmetric spacetimes

The objective of the present paper is to study weakly Ricci symmetric spacetimes. Among others, we prove that a weakly Ricci symmetric spacetime obeying Einstein’s field equation without cosmological constant represents stiff matter. Moreover, it is shown that the local cosmological structure of a weakly Ricci symmetric perfect fluid spacetime can be identified as Petrov type I, D or O. Next, we prove that a dust and dark fluid weakly Ricci symmetric spacetime satisfying Einstein’s field equation without cosmological constant is vacuum. Finally, we show the non-existence of radiation era in such a spacetime.

ON A CLASSIFICATION OF PARA-SASAKIAN MANIFOLDS

We consider para-Sasakian manifolds satisfying the curvature conditions

Certain results on generalized (k,\mu)-contact manifolds

P\cdot R=0

On a Type of Contact Metric Manifolds

,

Certain Curvature Properties of Generalized Sasakian-Space-Forms

P\cdot Q=0

On invariant submanifolds of Kenmotsu manifolds

and

on a class of k-contact manifolds

Q\cdot P=0

On Kenmotsu manifolds admitting a special type of semi-symmetric non-metric

, where

\phi-

R

connection

is the Riemannian curvature tensor,