Deformations and Einstein metrics I
This essay is about how to construct a new Einstein metric by an old one. Given an Einstein metric $\alpha$ and its Killing $1$-form $\beta$, donote $b:=\|\beta\|_{\alpha}$, we aim to determined the deformation factors $e^{\rho(b^2)}$ and $\kappa(b^2)$ such that $e^{\rho(b^2)}\sqrt{\alpha^2-\kappa(b^2)\beta^2}$ becomes an Einstein metric. In face, it will depends critically on the peculiarities of the Killing $1$-form. As the first article in this series, we assume $\beta$ satisfies two curcial conditions (5.3) and (5.4), which are simple, natural and occursing only on even-dimensional manifolds. In this essay, we just need to regard the metric as a quadratic form. Any other additional structure on manifolds, such as topological structure, complex structure, etc., are not used.