10

I'm looking for a specific symbol for typesetting my lecture notes in logic and set theory.

The character is used to define a new set from two existing sets alpha and beta (which are ordinals): Formula

In the above image, the \bot character is not what I want: instead of one vertical line I would like two parallel ones. Detexify found \coprod and \amalg (upside down product signs), which are close, but ideally the symbol that I'm looking for should be sans-serif.

In other words, I would like a symbol that is to \bot what \vDash is to \vdash. Unfortunately, I do not know the name of the operation that this symbol is representing, so meaning-based googling is ruled out.

Could anybody possibly help me out? I greatly appreciate your answers.

Community
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DCopperfield
  • 203
  • 1
    Look for \newcommand\independent in the list of symbols. On the other hand, it seems \amalg to me. – egreg Mar 07 '14 at 23:43
  • Very helpful thank you, the independent tip enabled me to find a solution (if you post that as an answer I can mark this question closed, or alternatively I can post the answer myself). Although I appreciate that you are probably sick of newbies posting questions asking for specific symbols in this forum, none of the tips listed in your link would have helped me to find the answer, as I seemingly encountered this symbol out of its usual context, and detexify didn't turn anything up. – DCopperfield Mar 07 '14 at 23:54

3 Answers3

10

In the Comprehensive List (texdoc symbols) one can find something near to what you want, looking for \independent. Here's a modified version:

\documentclass{article}

\makeatletter
\DeclareRobustCommand{\varamalg}{%
  \mathbin{\mathpalette\var@malg\perp}%
}

\newcommand\var@malg[2]{%
  \rlap{$\m@th#1#2$}\mkern6mu{#1#2}%
}
\makeatother

\begin{document}
\[
\alpha\varamalg\beta=\alpha\times\{0\}\cup\beta\times\{1\}
\]
\end{document}

enter image description here

Adjust \mkern6mu to suit.

egreg
  • 1,121,712
  • I'm a bit of a newbie; what's the reason behind using the @ symbol in your \newcommand def instead of a? – Jules Mar 08 '14 at 16:08
  • @user2615799 A different name must be used for the auxiliary macro; changing an a into @ is traditional. Observe that \makeatletter before the code was necessary. – egreg Mar 08 '14 at 16:23
9

I'm not sure of the exact aspect of what you require, but would not \upmodelsor \upVdashbelow be what you want? According to the name of the first symbol, it should be of use in model theory. These come from mdsymbol (math symbols for Myriad Pro), and the same exist in MnSymbol (mat symbols for Minion Pro).

enter image description here

Bernard
  • 271,350
7

Yet another solution (adjust -8mu to your needs)

\documentclass{article}
\usepackage{amsmath}

\newcommand{\dbot}{\mathbin{\text{$\bot\mkern-8mu\bot$}}}

\begin{document}

\[
\alpha\dbot\beta=\alpha\times\{0\}\cup\beta\times\{1\}
\]

\[
 A \dbot B_{A \dbot B_{A \dbot B}}
\]

\end{document}

enter image description here

karlkoeller
  • 124,410