boldfontsmath-modesymbols
To make Latin-letter variables bold I can use e.g. \mathbf{a}, but while putting Greek letters or symbols such as \nabla inside \mathbf doesn't cause any errors or warnings, it also doesn't do anything else.
What is the best way to make bold math symbols, in particular Greek letters and \nabla?
\boldsymbol uses \mathversion{bold}, but mathspec doesn't declare fonts for the bold math. Try this in your preamble:
\makeatletter
%\DeclareMathVersion{bold}
\fontspec{Minion Pro} %sets \zf@family to minion pro.
\SetSymbolFont{Latin:m:n}{bold}{EU1}{\zf@family}{bx}{n}
\SetSymbolFont{Latin:m:it}{bold}{EU1}{\zf@family}{bx}{it}
\SetSymbolFont{operators}{bold}{EU1}{\zf@family}{bx}{n}
\SetSymbolFont{Greek:m:n}{bold}{EU1}{\zf@family}{bx}{n}
\SetSymbolFont{Greek:m:it}{bold}{EU1}{\zf@family}{bx}{it}
\fontspec{Linux Libertine O}
\SetSymbolFont{Digits:m:n}{bold}{EU1}{\zf@family}{m}{n}
\makeatother
You have to carefully select the ranges and the symbols you need. Here's an example:
\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont[range=\mathup] {EB Garamond}
\setmathfont[range=\mathbfup]{EB Garamond}
\setmathfont[range=\mathbfit]{EB Garamond}
\setmathfont[range=\mathit] {EB Garamond}
\setmathfont[range={\partial,\nabla,\hslash}]{TG Termes Math}
\setmathfont[range=\mathit/{greek,Greek}]{Latin Modern Math}
\setmainfont{EB Garamond}
\begin{document}
\[ \int f(\alpha+x)=\sum\beta \]
Some text\dots
\begin{equation}
\begin{split}
\frac{\partial^2 \nabla}{\partial \nabla^2}&=x^2 + yimc^2=z^2 \\
&=\mathrm{x^2 + y^2 = z^2} \\
&=\mathbf{x^2 + y^2 = z^2}
\end{split}
\end{equation}
\begin{equation}
i\hbar \frac{\partial \psi }{\partial t}=\frac{\hbar c}{i}\left(\alpha _1\frac{\partial \psi }{\partial x^1}+\alpha _2\frac{\partial \Psi }{\partial x^2}+\alpha _3\frac{\partial \psi }{\partial x^3}\right)+\alpha _4mc^2\psi
\end{equation}
\end{document}
Best Answer
The AMS Short Math Guide recommends the
\boldsymboland\pmbcommands (and suggests that you use thebmpackage for the former to get a more powerful version than provided byamsmath).