# How do I delete the spacing for the equation below?

How do I delete the spacing between $$\lambda_{A}$$ and the parenthesis in the equation below?

$$\lambda_{A}\left(\bigcup\limits_{i=s}^{t} S_i\right)$$

• You could try putting \! between the two. – Gerry Myerson Jun 1 '20 at 3:50
• I really don't see a problem in the formatting you display in your question. – amWhy Jun 1 '20 at 16:07

The best way to do it is to use \mathop to make $$\rm\LaTeX$$ think that this is an operator:

$$\mathop{\lambda_A}\left(\bigcup_{i=s}^t S_i\right)\\\lambda_A\left(\bigcup_{i=s}^tS_i\right)$$

(There are also \mathbin and \mathrel for binary operators and relations respectively.)

As @GerryMyerson mentions in the comments, you can use the negative space command \!. You can even apply multiple of them if one doesn't have enough effect; the equations below have 0 up to 3 \! instances.

$$\lambda_{A}\left(\bigcup\limits_{i=s}^{t} S_i\right)$$ $$\lambda_{A}\!\left(\bigcup\limits_{i=s}^{t} S_i\right)$$ $$\lambda_{A}\!\!\left(\bigcup\limits_{i=s}^{t} S_i\right)$$ $$\lambda_{A}\!\!\!\left(\bigcup\limits_{i=s}^{t} S_i\right)$$

It's even possible to apply so many negative spaces that $$\lambda_A$$ ends up at the right side of the equation:

$$\lambda_{A}\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\left(\bigcup\limits_{i=s}^{t} S_i\right)$$

(but of course there is a much easier way to do so).