[FOM] Historical notation question
neilt at mercutio.cohums.ohio-state.edu
Wed Feb 25 12:30:04 EST 2004
On Wed, 25 Feb 2004 praatika at mappi.helsinki.fi wrote:
> Brian Postow was asking about the origin of the notation \Sigma_i and \Pi_i
> for the different levels of the arithmetic hierarchy.
> I don't think that Hirst and Sambin really managed to reply this question.
> I can't really confirm this now but I am pretty confident that this
> notation, *for the levels of the arithmetical hierarchy*, is due to John
> Addison (from the late 1950s).
If it wasn't Addison in the late 1950s, then it might have been Azriel
Levy, `A hierarchy of formulas in set theory.' Memoirs of the American
Mathematical Society, 57. American Mathematical Society, 1965 .
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