# Notation for the exclusive choice from the set

I have the following formula:

$$\Omega \subset \mathbb{R}^d,$$

where $d=2$ or $d=3$. But I find this style of notation quite cumbersome. Is there any way, how to note, that $d$ equals to 2 or 3 exclusively and in more elegant way?

• $d\in\{2,3\}$. That's all I can think of. – drhab Apr 13 '17 at 10:11
• @eenoku Personally, I'd prefer seeing the one you mentioned. – user228113 Apr 13 '17 at 10:12

## 1 Answer

You could write $\Omega\subset\mathbb{R}^2\lor \Omega\subset\mathbb{R}^3$, or $\Omega\in\mathcal{P}\left(\mathbb{R}^2\right)\bigcup\mathcal{P}\left(\mathbb{R}^3\right)$. Here $\mathcal{P}\left(S\right)$ denotes the power set of $S$, i.e. its set of subsets. (Note $S\in\mathcal{P}\left(S\right)$. If your use of $\subset$ was meant to imply proper subsets, that second option should be amended to $\Omega\in\mathcal{P}\left(\mathbb{R}^2\right)\bigcup\mathcal{P}\left(\mathbb{R}^3\right)\backslash\left\{\mathbb{R}^2,\,\mathbb{R}^3\right\}$.)