$dim(R / fR) = dim(R) -1$ if $f$ Regular

36 Views Asked by At

Let $R$ be Noetherian ring and $f \in R \backslash R^*$. According to Krull's principal ideal theorem we get for the Krull dimension $dim(R / fR) \le dim(R) -1$.

Why do we have an equality $dim(R / fR) = dim(R) -1$ if $f$ is a regular element?