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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:

$\operatorname{Re}z, \operatorname{Im}z$ ?

  • 4
    It's not "fractal". It's "fraktur". [Wikipedia](https://en.wikipedia.org/wiki/Fraktur).2012-11-10
  • 4
    This is an opinion question which is hard to answer. My own sense is that the fraktur notation is a bit older and less common nowadays.2012-11-10
  • 0
    Also, the correct "LaTeX-y" way of writing "Re" is "`\operatorname{Re}`" (or "`\DeclareMathOperator{\Re}{Re}`" in the preamble). See: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=newfunction2012-11-10
  • 7
    Because of Latex I'm actually here. I was wondering if there's a special reason why Latex defaults \Re and \Im to the Fraktur versions.2012-11-10
  • 3
    I see $\operatorname{Re}z, \operatorname{Im}z$ more often.2013-10-29
  • 0
    I think for the LaTeX history one should point to [this question](http://tex.stackexchange.com/questions/192692/why-does-amsmath-use-fraktur-for-real-and-imaginary-parts)2015-01-08
  • 1
    Actually there is a difference between how LaTeX typsets \Re and \Im and how \mathfrak{R} and \mathfrak{I} look on my computer, even though on this site they come out the same. The LaTeX defaults are curlier and fancier-looking than the mathfrak font ... I like the traditional look of those. But I would agree with the others that Re and Im are more conventional in current usages.2015-01-20
  • 3
    @GrumpyParsnip It's not an opinion question. Perhaps it's poorly defined what population to consider and how to measure, but after that's it's "just" a matter of measuring the the frequency and tell which is more common.2015-09-25
  • 1
    I am not sure I have ever seen even a single text which used $\Re$ and $\Im$.2015-10-26

2 Answers 2

10

I lean towards readability and I find $\operatorname{Re}z$ and $\operatorname{Im}z$ unambiguously clear.

  • 2
    Tastes vary, of course, but not being able to write or even recognize [fraktur](https://en.wikipedia.org/wiki/Fraktur) tends to favor readability. The fact that $\mathfrak{A}$ looks like an $U$, not an $A$, and $\mathfrak{P}$ looks like a $B$, not a $P$, has always slightly annoyed me.2015-08-24
  • 4
    Just becaue you lean one way or another doesn't make it more or less common.2015-09-25
  • 1
    @lhf I cannot believe your $\mathfrak{A}$ was actually an $A$ because it looks like a $U$, $\mathfrak{U}$ is $U$!2015-12-20
  • 0
    Oh I see it now.2015-12-20
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I prefer the fraktur notation. Firstly, it looks much more elegant. Secondly, it is unambiguous (for instance, Re is often used for Reynolds number).