[Tex/LaTex] Like \ell but for j

fontsmath-mode

I'm in a slightly annoying situation where I've used the letter j as an index, but now also want to use a lower case j for something else. Ideally I wouldn't want to do that, but changing either would require changing loads of other notation throughout the document. So I want to find a letter that's (a) clearly a lower case j, but (b) looks different from the usual math mode j.

I tried using \mathcal{j}, provided by the dutchcal package. With the (mandatory) style file I'm using it looks like this:

enter image description here

The two j's do look different, but it's a bit subtle and doesn't really give the impression that they're different characters with different meanings.

I also tried just using a unicode 𝒿, but that rendered as "??" with the style file I'm using.

I'm hoping to find a lower case j more in the style of \ell, with its very deliberate loop that makes it look quite distinct from a normal italic l:

enter image description here

Does such a glyph exist in any standard package that can be used with pdflatex?

Edit: I actually found a more satisfactory answer here using the Stix fonts, so I'm not sure if I should delete this question now. With that answer I get this:

enter image description here

It looks stylistically a bit weird due to the slope being even greater than the italic j. (Honestly, I don't like the way it looks in my document at all.) But at least it's very clear that the two j's are different.

Best Answer

The boondoxo calligraphics seem to fit the bill.

\documentclass{article}
\usepackage{amsmath}
\usepackage[cal=boondoxo]{mathalpha}

\newcommand\jay{\mathcal{j}}

\begin{document}
\[ \jay ( i \to j ) \]
\end{document}

Boondoxo font sample

You edited your answer to mention that you had found the STIX fonts. This has a similar style, but I personally prefer this less-slanted version.

You could also load this alphabet as \usepackage[scr=boondoxo]{mathalpha} and use it as \mathscr{j}, leaving \mathcal untouched.

While you ask about PDFTeX-compatible packages, anyone using unicode-math can get a very similar \mathscr alphabet with the command

\setmathfont{STIX Two Math}[
  range={scr,bfscr},
  Scale=MatchUppercase,
  StylisticSet=1 ]

If you need to use three different mathematical script alphabets in the same paper, yet you must use a legacy engine that limits you to sixteen 8-bit math alphabets, you might adapt the relevant commands from BOONDOX-uprscr.sty and uboondoxuprscr.fd and reconsider some of your choices in life.

\documentclass{article}
\usepackage{amsmath}

\DeclareFontFamily{U}{boondoxuprscr}{\skewchar \font =45}
\DeclareFontShape{U}{boondoxuprscr}{m}{n}{
    <-> BOONDOXUprScr-Regular}{}
\DeclareFontShape{U}{boondoxuprscr}{b}{n}{
    <-> BOONDOXUprScr-Bold}{}

\DeclareMathAlphabet{\mathboondoxo}{U}{boondoxuprscr}{m}{n}
\SetMathAlphabet{\mathboondoxo}{bold}{U}{boondoxuprscr}{b}{n}

\newcommand\jay{\mathboondoxo{j}}

\begin{document}
\[ \jay ( i \to j ) \]
\end{document}

You can also get this one symbol without using up one of your limited math alphabets.

\documentclass{article}
\usepackage{amsmath}

\DeclareFontFamily{U}{boondoxuprscr}{\skewchar \font =45}
\DeclareFontShape{U}{boondoxuprscr}{m}{n}{
    <-> BOONDOXUprScr-Regular}{}
\DeclareFontShape{U}{boondoxuprscr}{b}{n}{
    <-> BOONDOXUprScr-Bold}{}

\newcommand\jay{\text{\fontencoding{U}\fontfamily{boondoxuprscr}\fontshape{n}\selectfont j}}

\begin{document}
\[ \jay ( i \to j ) \]
\end{document}

This implementation does not support \boldsymbol{\jay}, but will use the bold version if the surrounding text is bold. It assumes you will be setting \bfseries\boldmath at the same time. To always use the medium weight, add \fontseries{m} before \selectfont.

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