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

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

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closed as unclear what you're asking by GEdgar, MJD, Giuseppe Negro, Harish Chandra Rajpoot, Silvia Ghinassi Feb 1 at 0:32

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.If this question can be reworded to fit the rules in the help center, please edit the question.

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I don't think it is standard notation. Where have you seen it? – Henning Makholm Sep 2 '12 at 20:24
    
I would say: Look in the previous pages of that book. – GEdgar Sep 2 '12 at 21:01
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Maybe it's a programming language... :-) – Asaf Karagila Sep 2 '12 at 21:46
    
Since HELP never came back, maybe we can close this. – GEdgar Jan 31 at 17:53

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

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Right, because $\mathbb{R}_{+}$ is ambiguous, as some authors use it for $[0,\infty)$ and some for $(0,\infty)$. – cyberSingularity Sep 2 '12 at 21:43
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I have seen it used this way fairly often. – Michael Greinecker Sep 2 '12 at 21:45
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--in economics books. – Michael Greinecker Sep 2 '12 at 21:54

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

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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.

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