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I'd like to use \v{C} as a math operator. However, if I write $\v{C}_r(S)$ or define \DeclareMathOperator{\Cech}{\v{C}}, the \v{C} symbol does not get shown at all. What is the proper way to handle this?

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\v is a text accent, the math equivalent is named \breve – daleif Feb 1 at 13:52
@daleif No: \breve is curved. The math equivalent is \check – Frédéric Grosshans Feb 1 at 14:14
@FrédéricGrosshans my bad, had a meeting to go to, so it was a little fast – daleif Feb 1 at 14:50
up vote 14 down vote accepted

\v(C) only works outside maths mode. For inside maths mode, use \check{C}. Thus (providing you are using the amsmath or mathtools packages), create your operator using:


and you can then do $\Cech_r(S)$ to get what you want.

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For completeness, you should mention that \DeclareMathOperator requires either the amsmath or mathtools packages. – Steven B. Segletes Feb 1 at 14:05
Note that if this operator is intended for comparison between two elements, you should use \mathbin{\check{C}}. – Dorian Feb 1 at 14:08
@StevenB.Segletes fair point. I assume the OP was doing that, but for the benefit of those who come here by google, I've added that as a parenthetical comment. – Robert Brignall Feb 1 at 15:25

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