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What does $\mathbb{R}^ {\times}$ mean? I cannot seem to find it anywhere.

James Woodward
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    The multiplicative group of the reals (so $\mathbb R-{0}$ under multiplication). – lulu Feb 22 '18 at 15:14
  • I have seen this notation for the set of elements having a multiplicative inverse. For the real numbers, these are all except $0$, so my guess is all real numbers, zero excluded. – Student Feb 22 '18 at 15:15
  • Interestingly $\mathbb R^+$ does not stand for the additive group of reals. – Umberto P. Feb 22 '18 at 16:30

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It is the set of the inversible elements of $\mathbb{R}$ considered as a ring. It is then $\mathbb{R}\setminus \{0\}$.

Netchaiev
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