\mathfrak didn't show correctly. (e.g., \mathfrak{0} in the tex file shows \mathfrak{5} in the generated pdf)

Question

Here is the text in the .tex file:

by learning multiple functions $\{f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} \}$

Here is the strange output in the pdf file:

Here are the environment used in the tex file:

\documentclass{sokendai_thesis} % https://github.com/koikezlemma/phd_thesis_template/blob/master/sokendai_thesis.cls
\begin{document}
by learning multiple functions ${f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} }$ \
$\forall{\mathfrak{k}}\in{\mathfrak{0},\cdots, \mathfrak{K}}$.
\end{document}

Does anyone know a possible reason for such strange output? Thanks!

Answer 1

If you copy the packages used in the class to the preamble and then delete any that you can delete while still showing the problem you end up with

\documentclass{article}
\usepackage{libertine} 
\usepackage[libertine]{newtxmath}
\begin{document}
by learning multiple functions ${f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} }$
$\forall{\mathfrak{k}}\in{\mathfrak{0},\cdots, \mathfrak{K}}$.
\end{document}

Simplest is to add \mathfrak back from amsfonts

\documentclass{article}
\usepackage{libertine} 
\usepackage[libertine]{newtxmath}
\let\mathfrak\relax
\usepackage{eufrak}
\begin{document}
by learning multiple functions ${f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} }$
$\forall{\mathfrak{k}}\in{\mathfrak{0},\cdots, \mathfrak{K}}$.
\end{document}

so it looks like an error in newtx

Answer 2

The AMS Fraktur font has glyphs for digits, the font newtxmath uses with the libertine option hasn't them and has blackboard bold digits instead (but not in the standard places, because \mathbb works differently than in amsfonts).

Here's the Fraktur font used by libertine:

Here's the AMS Euler Fraktur:

They're not really alike, so you may want to keep the libertine ones and just replace the digits. In order to blend with the heaviness of the libertine fonts I use the bold version.

\documentclass{sokendai_thesis} % https://github.com/koikezlemma/phd_thesis_template/blob/master/sokendai_thesis.cls
\AtBeginDocument{%
  \NewCommandCopy\TXmathfrak\mathfrak
  \RenewCommandCopy\mathfrak\ZLINmathfrak
}
\ExplSyntaxOn
\NewDocumentCommand{\ZLINmathfrak}{m}
 {
  \tl_map_function:nN { #1 } \zlin_mathfrak:n
 }
\cs_new_protected:Nn \zlin_mathfrak:n
 {
  \str_case:nnF { #1 }
   {
    {0}{__zlin_mathfrak_digit:n { 0 }}
    {1}{__zlin_mathfrak_digit:n { 1 }}
    {2}{__zlin_mathfrak_digit:n { 2 }}
    {3}{__zlin_mathfrak_digit:n { 3 }}
    {4}{__zlin_mathfrak_digit:n { 4 }}
    {5}{__zlin_mathfrak_digit:n { 5 }}
    {6}{__zlin_mathfrak_digit:n { 6 }}
    {7}{__zlin_mathfrak_digit:n { 7 }}
    {8}{__zlin_mathfrak_digit:n { 8 }}
    {9}{__zlin_mathfrak_digit:n { 9 }}
   }
   { \TXmathfrak{#1} }
 }
\cs_new_protected:Nn __zlin_mathfrak_digit:n
 {
  \text{\usefont{U}{euf}{b}{n}#1}
 }
\ExplSyntaxOff
\begin{document}
${f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} }$
$\forall{\mathfrak{k}}\in{\mathfrak{0},\cdots, \mathfrak{K}}$.
$\mathfrak{ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz}$
$\mathfrak{0123456789}$
\end{document}

Alternatively, use the AMS Euler Fraktur:

\documentclass{sokendai_thesis} % https://github.com/koikezlemma/phd_thesis_template/blob/master/sokendai_thesis.cls
\DeclareMathAlphabet{\mathfrak}{U}{euf}{m}{n}
\begin{document}
${f_\rho^{\mathfrak{0}}, f_\rho^{\mathfrak{1}}, \cdots, f_\rho^{\mathfrak{K}} }$
$\forall{\mathfrak{k}}\in{\mathfrak{0},\cdots, \mathfrak{K}}$.
$\mathfrak{ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz}$
$\mathfrak{0123456789}$
\end{document}