Is there a way to get physics to work with LuaLaTeX and unicode-math?

Question

When I try to use the \vb* macro of the physics package with LuaLaTeX and the unicode-math package, not a single OpenType math font seems to support bold characters.

\documentclass{article}
\usepackage{physics}  % Add \dv, \grad etc.
\newcommand\blurb{$\alpha \pi \lambda \vb*{\alpha\pi\lambda}$}
\usepackage[math-style=ISO,bold-style=ISO]{unicode-math}
%% Load 10 math fonts, plus two alternate/stylistic set variants
\setmathfont{Latin Modern Math}[version=LM]
\setmathfont{Stix Math}[version=Stix]
\setmathfont{XITS Math}[version=XITS]
\setmathfont{XITS Math}[StylisticSet=1,version=XITS1]
\setmathfont{Stix Two Math}[version=Stix2] % see http://stixfonts.org/
\setmathfont{Cambria Math}[version=Cambria]
\setmathfont{Asana Math}[version=Asana]
\setmathfont{Asana Math}[Alternate,version=AsanaAlt]
\setmathfont{TeX Gyre Pagella Math}[version=Pagella]
\setmathfont{TeX Gyre Termes Math}[version=Termes]
\setmathfont{TeX Gyre DejaVu Math}[version=DejaVu]
\setmathfont{Neo Euler}[version=Euler]
\setmathfont{Libertinus Math}[version=Libertinus]

\begin{document}
\renewcommand\arraystretch{1.8}
\begin{tabular}{@{}ll@{}}
Latin Modern & \mathversion{LM}      \blurb \\
Stix         & \mathversion{Stix}    \blurb \\
XITS         & \mathversion{XITS}    \blurb \\
XITS, StySet1& \mathversion{XITS1}   \blurb \\
Stix Two     & \mathversion{Stix2}   \blurb \\
Cambria      & \mathversion{Cambria} \blurb \\
Asana        & \mathversion{Asana}   \blurb \\
Asana Alt    & \mathversion{AsanaAlt}\blurb \\
Pagella      & \mathversion{Pagella} \blurb \\
Termes       & \mathversion{Termes}  \blurb \\
DejaVu       & \mathversion{DejaVu}  \blurb \\[0.5ex]
Neo Euler    & \mathversion{Euler}   \blurb \\[0.5ex]
Libertinus Math& \mathversion{Libertinus} \blurb
\end{tabular}
\end{document}

Answer 1

This is what physics does:

\DeclareDocumentCommand\vectorbold{ s m }{\IfBooleanTF{#1}{\boldsymbol{#2}}{\mathbf{#2}}} % Vector bold [star for Greek and italic Roman]
\DeclareDocumentCommand\vb{}{\vectorbold} % Shorthand for \vectorbold

It's really hard to understand the intentions of the package author.¹ According to ISO, vectors should be bold italic.² So it's quite strange that the package offers as standard the wrong notation and the right one as a variant.

Anyway, neither \boldsymbol nor \mathbf will do the right thing with unicode-math.

If you want to reproduce what physics does with pdflatex also when unicode-math is used, you could do

\documentclass{article}
\usepackage{unicode-math}
\usepackage{physics}

\RenewDocumentCommand{\vectorbold}{sm}{%
  \IfBooleanTF{#1}{\symbfit{#2}}{\symbf{#2}}%
}
\RenewCommandCopy{\vb}{\vectorbold}

\begin{document}

$v\vb*{v}\vb{v}$

$\alpha \pi \lambda \vb*{\alpha\pi\lambda}$

\end{document}

Compare with

% compile with pdflatex
\documentclass{article}
\usepackage{physics}

\begin{document}

$v\vb*{v}\vb{v}$

$\alpha \pi \lambda \vb*{\alpha\pi\lambda}$

\end{document}

The simplest strategy is to forget about physics that's buggy and has an overall weird syntax for commands, besides taking wrong decisions in several cases.

---

Footnotes

¹ \DeclareDocumentCommand is wrong here and throughout physics.sty.

² Not that I endorse the notation prescribed by ISO.

Answer 2

You wrote

When I try to use the \vb* macro of the physics package with LuaLaTeX and the unicode-math package, not a single OpenType math font seems to support bold characters.

and also commented

unicode-math is completely messing everything up

Not really. Just replace \vb*{\alpha\pi\lambda} with \symbf{\alpha\pi\lambda}.

Two additional observations:

• What's so important about using \vb*?

• I had to change \setmathfont{Neo Euler} to \setmathfont{Euler Math} to get your code to work without a hitch.

\documentclass{article}
\usepackage{physics}  % Add \dv, \grad etc.
\newcommand\blurb{$\alpha\pi\lambda\  \symbf{\alpha\pi\lambda}$}
\usepackage{unicode-math}
%% Load 10 math fonts, plus two alternate/stylistic set variants
\setmathfont{Latin Modern Math}[version=LM]
\setmathfont{Stix Math}[version=Stix]
\setmathfont{XITS Math}[version=XITS]
\setmathfont{XITS Math}[StylisticSet=1,version=XITS1]
\setmathfont{Stix Two Math}[version=Stix2]
\setmathfont{Cambria Math}[version=Cambria]
\setmathfont{Asana Math}[version=Asana]
\setmathfont{Asana Math}[Alternate,version=AsanaAlt]
\setmathfont{TeX Gyre Pagella Math}[version=Pagella]
\setmathfont{TeX Gyre Termes Math}[version=Termes]
\setmathfont{TeX Gyre DejaVu Math}[version=DejaVu]
\setmathfont{Euler Math}[version=Euler]
\setmathfont{Libertinus Math}[version=Libertinus]

\begin{document}
\begin{tabular}{ll}
Latin Modern   & \mathversion{LM}      \blurb \\
Stix           & \mathversion{Stix}    \blurb \\
XITS           & \mathversion{XITS}    \blurb \\
XITS, StySet1  & \mathversion{XITS1}   \blurb \\
Stix Two       & \mathversion{Stix2}   \blurb \\
Cambria        & \mathversion{Cambria} \blurb \\
Asana          & \mathversion{Asana}   \blurb \\
Asana Alt      & \mathversion{AsanaAlt}\blurb \\
Pagella        & \mathversion{Pagella} \blurb \\
Termes         & \mathversion{Termes}  \blurb \\
DejaVu         & \mathversion{DejaVu}  \blurb \\
Euler Math     & \mathversion{Euler}   \blurb \\
Libertinus Math& \mathversion{Libertinus} \blurb
\end{tabular}
\end{document}

Answer 3

Your issue is unrelated to luatex or the physics package, you would see the same in classic TeX.

\boldsymbol justt locally uses \boldmath to select \mathversion{bold} so this works well when you just have two math versions, normal and bold but if you define multiple math versions you need to also define multiple bold versions and arrange to switch them.

Here I just locally disable \mathversion so that \mathversion{anything} selects the bold version of the math version just selected, as this saves redefining the underlying commands.

I also just used FakeBold, although some of tehse do have a real bold math font that you coudl use, and a value of 3 is a bit excessive but makes it clear when debugging.

\documentclass{article}
\usepackage{amsmath}
\newcommand\blurb{$\alpha \pi \lambda \boldsymbol{\alpha\pi\lambda}$}
\usepackage[math-style=ISO,bold-style=ISO]{unicode-math}
%% Load 10 math fonts, plus two alternate/stylistic set variants
\setmathfont{Latin Modern Math}[version=LM]
%\setmathfont{Stix Math}[version=Stix]
\setmathfont{XITS Math}[version=XITS]
\setmathfont{XITS Math}[StylisticSet=1,version=XITS1]
\setmathfont{STIX Two Math}[version=Stix2] % see http://stixfonts.org/
%\setmathfont{Stix Two Math}[version=Stix2] % see http://stixfonts.org/
\setmathfont{Cambria Math}[version=Cambria]
\setmathfont{Asana Math}[version=Asana]
\setmathfont{Asana Math}[Alternate,version=AsanaAlt]
\setmathfont{TeX Gyre Pagella Math}[version=Pagella]
\setmathfont{TeX Gyre Termes Math}[version=Termes]
\setmathfont{TeX Gyre DejaVu Math}[version=DejaVu]
%\setmathfont{Neo Euler}[version=Euler]
\setmathfont{Euler Math}[version=Euler]
\setmathfont{Libertinus Math}[version=Libertinus]

\setmathfont{Latin Modern Math}[version=boldLM,FakeBold=3]
%\setmathfont{Stix Math}[version=Stix]
\setmathfont{XITS Math}[version=boldXITS,FakeBold=3]
\setmathfont{XITS Math}[StylisticSet=1,version=boldXITS1,FakeBold=3]
\setmathfont{STIX Two Math}[version=boldStix2,FakeBold=3] % see http://stixfonts.org/
%\setmathfont{Stix Two Math}[version=Stix2] % see http://stixfonts.org/
\setmathfont{Cambria Math}[version=boldCambria,FakeBold=3]
\setmathfont{Asana Math}[version=boldAsana,FakeBold=3]
\setmathfont{Asana Math}[Alternate,version=boldAsanaAlt,FakeBold=3]
\setmathfont{TeX Gyre Pagella Math}[version=boldPagella,FakeBold=3]
\setmathfont{TeX Gyre Termes Math}[version=boldTermes,FakeBold=3]
\setmathfont{TeX Gyre DejaVu Math}[version=boldDejaVu,FakeBold=3]
%\setmathfont{Neo Euler}[version=Euler]
\setmathfont{Euler Math}[version=boldEuler,FakeBold=3]
\setmathfont{Libertinus Math}[version=boldLibertinus,FakeBold=3]

\let\oldmathversion\mathversion
\def\bversion#1{\def\mathversion##1{\oldmathversion{bold#1}}}
\begin{document}


\renewcommand\arraystretch{1.8}
\begin{tabular}{@{}ll@{}}
Latin Modern & \mathversion{LM}\bversion{LM}      \blurb \\
%Stix         & \mathversion{Stix}\bversion{Stix}    \blurb \\
XITS         & \mathversion{XITS}\bversion{XITS}    \blurb \\
XITS, StySet1& \mathversion{XITS1}\bversion{XITS1}   \blurb \\
Stix Two     & \mathversion{Stix2}\bversion{Stix2}   \blurb \\
Cambria      & \mathversion{Cambria}\bversion{Cambria} \blurb \\
Asana        & \mathversion{Asana}\bversion{Asana}   \blurb \\
Asana Alt    & \mathversion{AsanaAlt}\bversion{AsanaAlt}\blurb \\
Pagella      & \mathversion{Pagella}\bversion{Pagella} \blurb \\
Termes       & \mathversion{Termes}\bversion{Termes}  \blurb \\
DejaVu       & \mathversion{DejaVu}\bversion{DejaVu}  \blurb \\[0.5ex]
Neo Euler    & \mathversion{Euler}\bversion{Euler}   \blurb \\[0.5ex]
Libertinus Math& \mathversion{Libertinus}\bversion{Libertinus} \blurb
\end{tabular}
\end{document}

---

In a normal document, even with unicode-math you would just use \setmathfont{...} to set up the normal version and \setmathfont[version=bold]{...} to set up bold math.

---

Also as Mico shows For these particular characters OpenType math fonts have the bold glyphs in the same font so locally redefining \boldsymbol to be \symbfit would also work.

Answer 4

The physics package uses the \boldsymbol command, I suspect because there is no bold-italic-math command in the LaTeX kernel. This sets \mathversion{bold}. You changed around the math versions but didn’t ever set that one up.

It also uses \mathbf in some places. By default, unicode-math sets \mathbf as the bold text font, for words in math mode, and makes the Unicode bold upright mathematical symbols available through \symbfup. You can override this, however, with the package option mathbf=sym. There are similar package options for \mathrm, \mathup, \mathit, \mathsf and \mathtt.

A MWE that sets up a bold math font and \mathbf:

\documentclass{article}
\usepackage{physics}  % Add \dv, \grad etc.
\newcommand\blurb{$\alpha \pi \lambda \vb*{\alpha\pi\lambda}$}
\usepackage[math-style=ISO,bold-style=ISO,mathbf=sym]{unicode-math}
\usepackage{newcomputermodern}

\setmathfont{NewCMMath-Book.otf}
\setmathfont{NewCMMath-Bold.otf}[version=bold]

\begin{document}
\blurb
\end{document}

If you genuinely need to change between different math fonts in the same document, such as between sans-serif and serif, you want to define math fonts for version=sans and possibly version=boldsans. Use the alphabets like \symsfup and \symbfit whenever you can, but it is also possible to define new commands analogous to \boldsymbol, e.g.:

%% Based on the definition of \boldsymbol from amsbsy.sty"
\makeatletter
\DeclareRobustCommand{\sanssymbol}[1]{%
  \begingroup%
  \let\@nomath\@gobble \mathversion{sans}%
  \math@atom{#1}{%
  \mathchoice%
    {\hbox{$\m@th\displaystyle#1$}}%
    {\hbox{$\m@th\textstyle#1$}}%
    {\hbox{$\m@th\scriptstyle#1$}}%
    {\hbox{$\m@th\scriptscriptstyle#1$}}}%
  \endgroup}
\makeatother

If you’re reconsidering whether you want to use physics at all, see @egreg’s answer. (I respectfully disagree with his suggestion to use low-level formatting commands in the body of your document rather than high-level semantic markup, especially if you might have to copy-and-paste an equation into a document for legacy TeX or change to your publisher’s house style.)