Unwanted Space Between Vertical Bar and Math Operator

Question

In my preamble, I have defined a math operator by writing DeclareMathOperator{Av}{Av}. When I use the command $Av$, there is a small amount of horizontal space on each side of the operator. Usually, this spacing looks good, but not when I put it inside absolute value symbols. For example, if I write $|Av(n)|$, then there is a little vertical space between the first vertical bar and the A. Is there a way to define my operator in my preamble so that this spacing does not appear?

Davislor · Answer

The comments already gave you a couple of good solutions, lvert Av(n) rvert and defining an abs command using DeclarePairedDelimiter from mathtools.
The reason you’re having this problem is the spacing between atoms of different math classes.  A command you define with declaremathoperator has the same mathop spacing as log or sin, so if you try to bracket it with two mathord atoms, you’ll get spacing like 2 log x.  You instead want your delimiters to have mathopen and mathclose spacing, like ( and ) or [ and ], and lvert and rvert do.

Unwanted Space Between Vertical Bar and Math Operator

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