Several authors use a circled perpendicular sign to indicate orthogonal direct sums.
What is the appropriate way to implement this, so you can use it like \oplus and \bigoplus ?
[Tex/LaTex] Orthogonal direct sum
symbols
Related Solutions
To negate the \perp (perpendicular) symbol, the command \not\perp provides a simple solution, but this negated symbol doesn't look that great IMHO:
If you load the mathabx package, you get the command \notperp which looks pretty good, as does now the output of \not\perp. The same effect can be achieved if you load either the MnSymbol package or the fdsymbol package and use the command \notperp (same name used by both packages). Notice, though, that even if you load the MnSymbol of the fdsymbol package, the output of \not\perp still looks pretty bad, i.e., as bad as if you hadn't loaded any extra package at all.
Addendum: Following a request by the OP, here's an MWE that shows how to load the mathabx package and generate the symbol using the package's \notperp macro, as well as with \not\perp"
\documentclass{article}
\usepackage{mathabx}
\begin{document}
$a \notperp b$, $c \not\perp d$
\end{document}
Next, here's an MWE that shows the use of the MnSymbol package to generate these symbols:
\documentclass{article}
\usepackage{MnSymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}
Finally, with the use of the fdsymbol package and its \nperp macro:
\documentclass{article}
\usepackage{fdsymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}
Happy TeXing!
Ah well it all depends.
In the default setup as commented in the linked question they are the same symbol but with different mathclass (so different spacing) \bot is a mathord (like an ordinary letter) and \perp is a relation (like <). Relations get more space either side if used between two symbols but in M^{\perp} the mathlist that forms the superscript only has one atom, so there is no additional spacing applied. That means that M^\bot and M^\perp produce identical output.
You could argue that \bot was better as it is naturally a symbol and a relation is not intended here.
Or you could argue that \perp is better as bot refers to a logical notion of bottom/false whereas perp refers to perpendicular which is somehow semantically related to orthogonal.
Or you could argue that they make identical output so it makes no difference and you can use either.
Best Answer
To summarize the comments, here are the options currently available.
The
mathabxprovides\obotand\bigobot. These symbols look likeIf you don't want to include all the
mathabxsymbols (they overwrite many Computer Modern symbols), then you can use the following setup (taken from Importing a Single Symbol From a Different Font):Unicode additionally defines ⦹ U+29B9 (circled perpendicular), but doesn't provide a big counterpart. The symbol can be used with the
unicode-mathpackage and LuaLaTeX or XeLaTeX. As of summer 2012 only the XITS and Cambria math fonts include the symbol. In XITS Math it looks likeThe corresponding TeX code is
The Unicode also has
\obot, looking similar to the example above, but doesn't provide\bigobot. You could try to fake the large symbols with something like{\text{\Large$\operp$}}\limits_{i∈I} V_i, but the scaling will make the symbol heavier:The STIX fonts LaTeX package is available, but not yet in TeX Live (as of this writing). After installing it you can use (with normal pdfLaTeX)
to get an output similar to the above.
If you only want the
\operpsymbol from STIX, you can set it up yourself:In general have a look at How to look up a symbol or identify a math symbol or character? to see how you can find a specific symbol.