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Let $X$ be a normal variety and $D \subset X$ be a prime divisor which is also normal. It is well-known that we can take a resolution $f: W \to X$ of $X$ such that $$\DeclareMathOperator{\Supp}{\operatorname{Supp}} \DeclareMathOperator{\Exc}{\operatorname{Exc}} \Supp(\Exc(f)) \cup \tilde D $$ has simple normal crossings (here $\Exc(f)$ is the exceptional locus $f$ and $\tilde D$ is the strict transform of $D$).

My question: can we take $f$ such that the induced morphism $f_D: \tilde D \to D$ is also a log resolution (i.e. $\Supp(\Exc(f_D))$ has simple normal crossings)?

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  • $\begingroup$ You are right, this needs more love, but I think it's still possible. Cheers, $\endgroup$ Commented Jul 20, 2021 at 3:13
  • $\begingroup$ If $D$ is a Cartier divisor, then $Sing(X)\cap D\subseteq Sing(D)$, so it is at least of codimension 2 in $D$, in which case that equality is true if you restrict to strict resolutions (i.e., only blow up centers inside $Sing(X,D)$). $\endgroup$ Commented Jul 20, 2021 at 3:21
  • $\begingroup$ Thank you! It makes sense to me when $D$ is Cariter. $\endgroup$
    – Li Yutong
    Commented Jul 20, 2021 at 4:03

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