Comoving suppression mechanism and cosmological constant problem

In this paper, we assume that the observer is fixed in a comoving frame of reference with $g_{00}=\frac{\lambda}{\Lambda}$, where $\lambda$ and $\Lambda$ denote the comoving parameter and the cosmological constant, respectively. By using the {\it comoving suppression mechanism} and {\it Mach's principle} (the latter of which is used to determine the comoving parameter $\lambda$), we calculate the vacuum energy density of quantum fluctuation field in the above-mentioned comoving frame of reference. It is shown that in such a comoving frame of reference, the cosmological constant will greatly decrease by many orders of magnitude (if Mach's principle is applied to this calculation, then it will be shown that $\Lambda$ is reduced by about 120 orders of magnitude). Additionally, we briefly discuss the related topics such as the varying observed speed of light ($\frac{{\rm d}c}{{\rm d}t}={\mathcal O}(10^{-9}{\rm m/s}^{2})$) and the mystery of anomalous acceleration ($\sim 10^{-9}{\rm m/s}^{2}$) acquired by the Pioneer 10/11, Galileo and Ulysses spacecrafts.