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I'd like to write a majuscule delta-like symbol in LaTeX but I can't find it's syntax anywhere. You can see the symbol on equation (12) of the following paper:

"Two-Frame Motion Estimation Based on Polynomial Expansion".

enter image description here

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5 Answers 5

32

Note that the document uses Springer's LNCS style. In this style, all Greek letters are in italics, and vectors are denoted by boldface.

Most likely the bold italic Delta is produced in this particular case by something similar to this:

\documentclass{llncs}
\begin{document}
$\vec{\Delta}$
\end{document}

The result is:

llncs

Note that if you used the article class, the same code would produce a normal Delta with an arrow:

article

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That is just $\Delta$ which is different from $\delta$. LateX symbols are case-sensitive. See any of the LaTeX cheat sheets as e.g. this one a U Colorado.

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  • Thanks for the cheat sheet, but it is not a regular delta. Is as if it was in italic. Please check the paper to see what I'm talking about.
    – Renan
    May 23, 2011 at 2:37
  • Same symbol, different font. May 23, 2011 at 2:50
  • 3
    @Renan: What if you typeset it in italics, e.g. \mathit{\Delta}? May 23, 2011 at 17:01
  • 1
    The cheat sheet link is dead. Redirects to the homepage.
    – HSchmale
    Sep 21, 2015 at 17:41
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If one really wants a bold italic Delta, the way to go is

\usepackage{bm}
\newcommand{\bfitDelta}{\bm{\mathit{\Delta}}}

Of course, one could write every time \bm{\mathit{\Delta}}.

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  • Note that \mbfitDelta is what existing packages use.
    – Davislor
    May 20, 2023 at 19:43
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There are several such symbols in Unicode, and hence unicode-math. The Laplacian operator ∆ (U+2206) is \increment. This is semantically a math operator instead of a Greek letter. It provides △ as either the binary operator \bigtriangleup or the letter-like symbol \triangle, and ▵ as \vartriangle. There are also the letters Δ (\mupDelta or \symup\Delta), 𝛥 (\mitDelta or \symit\Delta), 𝚫 (\mbfDelta or \symbfup\Delta) and 𝜟 (\mbfitDelta or \symbfit\Delta). \Delta might mean either the upright or slanted letter. Finally, there are the sans-serif math letters 𝞓 (\mbfitsansDelta or \symbfsfup\Delta) and 𝝙 (\mbfsansdelta or \symbfsfit\Delta) for tensors.

You appear to want to use slanted capital Greek letters by default, including for the Δ symbol. You can acoomplish that with the following:

\documentclass{article}
% To fit into the width at TeX.SX:
\usepackage[paperwidth=10cm]{geometry}
\usepackage[math-style=ISO]{unicode-math}

\begin{document}
Scalar \( \Delta t \), vector \( \symbf{\Delta x} \),
Laplacian \( \increment f(p) \).
\end{document}

Font sample

You might instead prefer to use upright Delta symbols even though Greek letters such as Γ are slanted in ISO style:

\documentclass{article}
% To fit into the width at TeX.SX:
\usepackage[paperwidth=10cm]{geometry}
\usepackage[math-style=ISO]{unicode-math}

\begin{document}
Scalar \( \symup\Delta t \), vector \( \symbfup\Delta\symbf{x} \),
Laplacian \( \increment \Gamma(p) \).
\end{document}

Font sample

Although \symbf works only on the letters and not the operators, unicode-math supports \boldmath if you load a math font that has a bold weight (currently XITS Math, Libertinus Math and Minion Math). You can also \setmathfont[version=bold]{XITS Math Bold}. The \boldsymbol\increment (from amsbsy.sty) will work.

If you want a bold slanted Δ symbol for your bold slanted vector symbols in PDFTeX, I recommend the isomath package.

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This looks very much like \Updelta (\usepackage{ upgreek })

UpDelta vs standard Delta

As you can see here, when compared with the standard Delta, the Updelta has an italic look to it.

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    Why \Updelta? It is pretty obvious that the Delta in the question is italic. Jun 16, 2016 at 8:35
  • @HenriMenke I think that someone visiting this question may be interested in other alternatives, and as you can see from the above comparison the Updelta symbol certainly looks more like the italic delta than the standard delta symbol.
    – JStrahl
    Jun 21, 2016 at 11:56
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    Even though it might be useful, it does not answer the question and according to site policy an answer has to address the question. Also we do not want to clutter the answer section with might-be-useful posts. Neither does the symbol reproduce the one in the question, nor is it italic (see this picture). Jun 21, 2016 at 13:29

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