Remove ugly space before \bigvee

Question

For example, I have the next code:

\documentclass[12pt]{article}
\usepackage[english, ukrainian]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage{amsmath}

\begin{document}
    \section{Секція 1}
    {\sffamily Диз'юктивне прозкладання булевої функція за \(k\) змінними:}
    \begin{gather}
        f(x_1,\ldots,x_k,x_{k+1},\ldots,x_n) =\bigvee_{(\sigma_1,\sigma_2,\ldots,\sigma_n)}x_1^{\sigma_1}\land x_2^{\sigma_2}\land \ldots \land x_k^{\sigma_k}\land f(\sigma_1,\sigma_2,\ldots,\sigma_k, x_{k-1},\ldots,x_n)
    \end{gather}
\end{document}

It produces But I wold like to get rid of space before (and maybe after) \bigvee permanently. I do know about \hspace{} but I would have to write that damn \hspace{\bigveespace} or some command every time I use \bigvee, so yes, that isn't what I want to do.

How could I do it?

Answer 1

You need to apply two fixes, not just one fix:

• Mandatory: Introduce a line break in the formula. I suggest you place the line break after the = symbol while employing a multline environment.
• Optional: Eliminate the whitespace on either side of \bigvee. The mathtools package, a superset of the amsmath package, provides two methods for accomplishing this. Both methods are illustrated in the following example. For the case at hand, both methods happen to produce the same outcome; this is not true in general.

\documentclass[12pt]{article}
\usepackage[english, ukrainian]{babel}
%%\usepackage[utf8]{inputenc} % that's the default nowadays
\usepackage[T1]{fontenc}

\usepackage{mathtools} % 'mathtools' is a superset of 'amsmath'

\begin{document}

%% (a) the \mathclap approach
\begin{multline}
 f(x_1,\dots,x_k,x_{k+1},\dots,x_n)  \\
 =\bigvee_{\mathclap{(\sigma_1,\sigma_2,\dots,\sigma_n)}}
   x_1^{\sigma_1}\land x_2^{\sigma_2}\land\dots\land x_k^{\sigma_k}\land 
   f(\sigma_1,\sigma_2,\dots,\sigma_k, x_{k-1},\dots,x_n)
\end{multline}

%% (b) the \smashoperator approach
\begin{multline}
 f(x_1,\dots,x_k,x_{k+1},\dots,x_n)  \\
 =\smashoperator{\bigvee_{(\sigma_1,\sigma_2,\dots,\sigma_n)}}
   x_1^{\sigma_1}\land x_2^{\sigma_2}\land\dots\land x_k^{\sigma_k}\land 
   f(\sigma_1,\sigma_2,\dots,\sigma_k, x_{k-1},\dots,x_n)
\end{multline}

\end{document}