5
$\begingroup$

What does $\mathbb{R}_{++}$ mean?

I know $\mathbb{R}_+$ means all non-negative real numbers, but I have no clue what $\mathbb{R}_{++}$ means.

  • 0
    Since HELP never came back, maybe we can close this.2016-01-31

3 Answers 3

7

It usually means the set of all positive real numbers, $\mathbb{R}_{++} = (0,\infty)$. Of course, there might be more symbols for this set.

  • 0
    But don't most math books use $\mathbb{R}^{+}$ instead?2017-04-29
5

From my Course: Probabilistic Methods in Finance, we denoted $R+, R++$ like so: $R+ =\{x\in R : x\ge0\}$ $R++ =\{x\in R : x≫0\}.$

  • 0
    What does $ x≫0 $ mean? Shouldn't it be \mathbb{R}_{++} =\{x\in \mathbb{R} : x>0\}.2017-08-14
1

Im not completely sure , but i believe it means strictly positive. Thus not the negative reals NOR zero.

Well assuming the context is real numbers that is.

I believe it is used in countries where R+ is meant to include 0. In most countries R+ does not include 0 , hence the extra symbol.

It might help to read over again to get an idea.