TITLE: What's more common? Re / Im or Fraktur-R / Fraktur-I for real / imaginary part?
QUESTION [27 upvotes]: Title says it all. What's more common? Is there one to prefere (maybe due to some norm)?
This:
$\operatorname{\mathfrak{R}} z, \operatorname{\mathfrak{I}} z$
or that:
$\operatorname{Re}z, \operatorname{Im}z$ ?

REPLY [6 votes]: I prefer the fraktur notation. Firstly, it looks much more elegant. Secondly, it is unambiguous (for instance, Re is often used for Reynolds number).