# For Hom and H*(X,Z) — which fonts? [closed]

This is a question about style, I am debating whether the math operator \Hom should be just

\DeclareMathOperator{\Hom}{Hom}


or if it should be some variant like

\DeclareMathOperator{\Hom}{\mathnormal{Hom}}


The reason I'm even considering this is because I'm using the eulervm package. Also, when I write something like cohomology $H^*(X,Z)$, I do not use \text{H} but leave eulervm's mathematical font.

What do you think? Does the question make sense?

Here is a minimal example with the two choices.

\documentclass{amsart}
\usepackage{eulervm}
\begin{document}
$\operatorname{Hom}(A,B) = 0$
$\mathnormal{Hom}(A,B) = 0$
$H^2(X,Z) = 0$
$\operatorname{H}^2(X,Z) = 0$
\end{document}


## closed as off-topic by cfr, Gonzalo Medina, Svend Tveskæg, Masroor, MicoFeb 4 '15 at 4:11

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question does not fall within the scope of TeX, LaTeX or related typesetting systems as defined in the help center." – cfr, Svend Tveskæg
If this question can be reworded to fit the rules in the help center, please edit the question.

• Some of this is just style choice but I'd use \DeclareMathOperator{\Hom}{Hom} for Hom and $H$ for H. Don't use \text for math (just use it for embedded bits of sentence) you could use \mathrm{H} but I think just using the math italic H is more usual. Note DeclareMathOperator gives \Hom the correct spacing not just the correct font, so is better than \mathrm}{Hom} (it is \mathop{\mathrm{Hom}} ) – David Carlisle Jan 30 '15 at 17:38
• @DavidCarlisle: I agree 100% when one does not use eulervm (I also changed \text to \operatorname, which is what I had originally intended, thanks). But with it, the fonts are drastically different, that's why I'm not so sure. – user125763 Jan 30 '15 at 17:41
• That's a stylistic decision that you can postpone until the end, provided you define macros for Hom and H. – egreg Jan 30 '15 at 17:42
• IMHO it should be \DeclareMathOperator\Hom{Hom} and \newcommand*\HH{\mathrm{H}}, but it's a stylistic question rather than a TeXnical one -- I'm not sure if it's on-topic here... – yo' Jan 30 '15 at 17:44
• I'm voting to close this question as off-topic because it's about an stylistic option (open to opinin-based answers) and not a really TeXnical issue. – Gonzalo Medina Feb 4 '15 at 3:05

Both “Hom” and ”H” are similar to “log”, so they should be typeset in the text font (upright). However it's not a sin to have different opinions.

The most important thing is that you use macro definitions:

\DeclareMathOperator{\Hom}{Hom}% preferred
%\DeclareMathOperator{\Hom}{\mathnormal{Hom}}% with Euler type
\DeclareMathOperator{\HH}{H}% preferred
%\DeclareMathOperator{\HH}{\mathnormal{H}}% with Euler type


Not \H, because it's already reserved.

In the body of the document you'll use only \Hom and \HH. This way, you can delay the choice to the last moment.

Tightening the space in “Hom” in Euler type is not a choice: look at the following picture to see why.

Here's the source for the image

\documentclass{amsart}
\usepackage{eulervm}
\begin{document}

\newcommand{\test}[1]{$H\mkern-#1mu o\mkern-#1mu m$\par}

\test{0}\test{0.2}\test{0.4}\test{0.6}\test{0.8}\test{1}

\end{document}

• why is tightening the space not an option? – user125763 Jan 30 '15 at 19:20
• @user125763 Did you try? – egreg Jan 30 '15 at 20:30
• I don't know how – user125763 Jan 30 '15 at 20:31
• uhm, I guess it's a little improvement but not by much. Can I ask how you did it? – user125763 Jan 30 '15 at 21:31

The purpose of this answer is only to disagree with egreg that Hn(X) should be typeset with an upright H. He claims that H is similar to log, and thus should be typeset similarly.

I believe instead that Hn is a functor F just like C(X), πn(X), Ωk(X). All of these are written in italics, just like any other mathematical object, and Hn(X) should be no different.

• I think I agree. But if all functors should be typeset the same, then one would try and make the case that Hom is also a functor, hence it should be typeset (in case your rebuttal involves the sheaf Hom: I usually put an underline to denote that). – user125763 Jan 31 '15 at 12:54