What is this symbol?

Question

I am reading "Sets, Numbers and Topology" by Masahiko Saito.
And the following symbol is used to denote the set of equivalence classes in the book.

What is this symbol?
$J$?
$T$?

It is an uppercase F letter, in a fancy font. You can't miss it thanks to the small horizontal bar. — , Feb 21 '19 at 13:14
First off, there is a dedicated TeX.stackexchange site. This is probably better to ask there. Second, it looks like it belongs to the mathpzc font, but I can't make it here to try it out and/or demonstrate. — Arthur, Feb 21 '19 at 13:28

score 5 · Answer 1 · answered Feb 21 '19 at 13:33

5

I belive it represents the Fourier transform. I use it frequently and am always fighting font types and editors to try to get it to render nicely.

answered Feb 21 '19 at 13:33

Paul Childs

Bernard · Accepted Answer · 2019-02-22T09:57:37.407

4

It is a calligraphic F. The closest looking I know for use with LaTeX is the dutchcal font (available on CTAN):

edited Feb 22 '19 at 09:57

answered Feb 21 '19 at 13:42

Bernard

score 1 · Answer 3 · answered Feb 21 '19 at 13:23

1

I suspect it is based on a Fraktur F, like or $\mathfrak{F}$

In MathJax, you can use \mathfrak{F}

answered Feb 21 '19 at 13:23

Henry

It is more rounded than a Fraktur. – Feb 21 '19 at 13:26
$\mathscr{F}$, or $\mathcal{F}$, or $\mathit{F}$, or one of the possibilities given here. – Dietrich Burde Feb 21 '19 at 13:32

3 Answers3