math-modespacing
I'm trying to use \cdotas a dummy for a function argument in the following expression
C(\cdot\mid\mathcal{F}_{t-1})
However, the above produces more space to the right of the dot than to the left. I'd like the spacing to be symmetrical. I've tried using {}on either side but haven't been able to get the desired result.
I didn't have the fonts so I changed the operator, but I think \mathinner does what you want here, puts some space before an ord, and doesn't stop a bin atom having bin spacing,
Top version in each of these:
\documentclass{article}
\usepackage{amsmath,amssymb}
\newcommand{\coerceSub}[3]{(\mathord{#1}{\smallfrown}\mathord{#2})_{#3}}
\begin{document}
In an operator application, the ``mathrel'' version looks better.
\begin{gather}
% OK
\mathinner{\coerceSub uv1} x \\
\mathrel{\coerceSub uv1} x \\
% Not OK: no space between operator and operand
\coerceSub uv1 x
\end{gather}
In an operator composition, the plain version looks better.
\begin{gather}
\mathinner{\coerceSub uw1} \circ c \\
% Not OK: no space between \circ and c
\mathrel{\coerceSub vw1} \circ c \\
% OK
\coerceSub vw1 \circ c
\end{gather}
\end{document}
Three suggestions:
Define a macro/command if you're using something multiple times. It promotes consistency and would make your life much easier if you decide to change things later on, even just a little bit. For example, \itemmul{<mat1>}{<mat2>}. As reference, see Consistent typography.
You can modify the spacing around a relation/operator to your liking by changing it into an ordinal symbol first, and then specifying the kerning using \mkern. Ordinals are obtained by wrapping the relation/operator in braces, like {\cdot} or using \mathord{\cdot}. Math kerning is specified in mus (or math units).
Using the above suggestions, here's a take on your spacing:
\documentclass{article}
\usepackage{amssymb}% http://ctan.org/pkg/amssymb
\newcommand{\itemmul}[2]{% \itemmul{<mat1>}{<mat2>}
\widehat{#1}\mkern1mu{\cdot}\mkern1mu\widehat{#2}% itemwise-multiplication
}
\begin{document}
\[
(\itemmul{w}{S})^{\intercal}\widetilde{H}(\itemmul{w}{S})
\]
\end{document}
Best Answer
Since you want to use the blank next either between an opening atom (the open parenthesis) and a relation atom (
\mid) or between a relation atom and a closing atom, you can define\blankto be a relation symbol:The trick is that TeX doesn't add space in cases
or