Combining two fonts with LuaLaTeX

Question

I would like to use Concrete fonts as the math font (the same font use for math in the package ccfonts or concmath) for one document while using GFS Neohellenic for blackboard letters (because the ccfonts package doesn't implement blackboard letters for this font family) and I would like to set Times New Roman as text font only. I already asked a question on how to get blackboard letters for the ccfonts package here : How do I select a blackboard bold font for Concrete math?. The following MWE was given to me to achieve what I wanted :

\documentclass{article}
\usepackage[math-style=ISO]{unicode-math}
\usepackage[paperwidth=10cm]{geometry} % Format a MWE for TeX.SX
\setmainfont{CMU Concrete}[
  Ligatures=Common,
  UprightFont=cmunorm.otf,
  BoldFont=cmunobx.otf,
  ItalicFont=cmunoti.otf,
  BoldItalicFont=cmunobi.otf ]
\setmathfont{GFS Neohellenic Math}[Scale=MatchLowercase]
\setmathfont{cmunoti.otf}[range=it]
\setmathfont{cmunorm.otf}[range=up]
\begin{document}
\noindent%
Let ( (x,y) \in \mathbb{R} \times \mathbb{R} )
such that ( \sqrt{x^2 + y^2} \leq \varepsilon ).
\end{document}

I never used LuaLaTeX and I don't understand how to mix Times New Roman and Concrete font in the same document. So here is my question :

How can I mix Concrete font as math font, Times New Roman as main font et GFS Neohellenic for blackboard letters in the same document using LuaLaTeX ?

I would like a MWE or links to ressources that explain how to mix fonts in LuaLaTeX.

Answer 1

A reference comparison of some TeX Gyre Math fonts, so just an illustration, not an answer.

Blue is the neohellenic bb.

MWE

\documentclass{article}
\usepackage{xcolor}
\usepackage[math-style=ISO]{unicode-math}
\setmainfont{Times New Roman}
\setmathfont{TeX Gyre Bonum Math}
\newcommand\blueneoh{\setmathfont{GFS Neohellenic Math}[Scale=MatchLowercase,range=bb,Colour=blue]}
\newcommand\testtext[1]{#1\par\setmathfont{#1}\blueneoh\noindent%
Let $ (x,y) \in \symbb{R} \times \symbb{R} $
such that $ \sqrt{x^2 + y^2} \leq \varepsilon $.\par\bigskip}
\begin{document}
\testtext{TeX Gyre Bonum Math}
\testtext{TeX Gyre DejaVu Math}
\testtext{TeX Gyre Pagella Math}
\testtext{TeX Gyre Schola Math}
\testtext{TeX Gyre Termes Math}
\testtext{latinmodern-math}
\end{document}

Answer 2

Your request

"How can I mix Concrete font as math font, Times New Roman as main font et GFS Neohellenic for blackboard letters in the same document using LuaLaTeX?"

is not quite clear for me: Concrete fonts are text fonts usually associated with the AMS Euler fonts for maths.

One the other hand, Ulrik Vieth has issued (long ago, 1999) the concmath package which borrows the math letters (upright and italics) from the Concrete text fonts, unfortunately that is all metafont, not meant to be used with LuaTeX. I am not aware of any Concrete Math (Opentype) font usable with LuaTeX.

If you can accept Euler (upright) maths, you could try something like this:

\documentclass{article}
\usepackage[math-style=upright]{unicode-math}
\setmainfont{Times New Roman}
\setmathfont{Neo Euler}              % No math italics
\setmathfont{GFS Neohellenic Math}[Scale=MatchUppercase,range=bb]
\begin{document}
Let $(x,y) \in \symbb{R} \times \symbb{R}$
such that $\sqrt{x^2 + y^2} \leq \varepsilon$.
\end{document}

which outputs as:

Update 16th January 2022: the new (experimental) concmath-otf package available on CTAN and in the latest TeXLive provides a Concrete-Math OpenType font usable with LuaTeX and XeTeX engines.

is the output of

\documentclass{article}
\usepackage{unicode-math}
\setmainfont{Times New Roman}
\setmathfont{Concrete-Math.otf}
\begin{document}
Let $(x,y) \in \symbb{R} \times \symbb{R}$
such that $\sqrt{x^2 + y^2} \leq \varepsilon$.
\end{document}

Answer 3

Change the \setmainfont command to \setmainfont{Times New Roman}. That sets the text font.