| Popis: |
The present paper aims to investigate $(m,\rho)$-quasi-Einstein metrices on almost co-K\"ahler manifolds $\mathcal{M}$. It is proven that if a $(\kappa,\mu)$-almost co-K\"ahler manifold with $\kappa<0$ is $(m,\rho)$-quasi-Einstein manifold, then $\mathcal{M}$ represents a $N(\kappa)$-almost co-K\"ahler manifold and the manifold is locally isomorphic to a solvable non-nilpotent Lie group. Next, we study the three dimensional case and get the above mentioned result along with the manifold $\mathcal{M}^3$ becoming an $\eta$-Einstein manifold. We also show that there does not exist $(m,\rho)$-quasi-Einstein structure on a compact $(\kappa,\mu)$-almost co-K\"ahler manifold of dimension greater than three with $\kappa<0$. Further, we prove that an almost co-K\"ahler manifold satisfying $\eta$-Einstein condition with constant coefficients reduces to a $K$-almost co-K\"ahler manifold, provided $ma_{1} \neq (2n-1)b_{1}$ and $m \neq 1$. We also characterize perfect fluid spacetime whose Lorentzian metric is equipped with $(m, \rho)$-quasi Einstein solitons and acquired that the perfect fluid spacetime has vanishing vorticity, or it represents dark energy era under certain restriction on the potential function. Finally, we construct an example of an almost co-K\"ahler manifold with $(m,\rho)$-quasi-Einstein solitons. |
