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Tagged with ordinal-analysis reference-request
2 questions
11
votes
1
answer
500
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What system suffices to show the strength of PRA is $\omega^\omega$?
Russell O'Connor wrote in 2009 (link):
PRA has consistency strength equivalent to the well-foundness of $\omega^\omega$, which can be stated again as the termination of some other program on all ...
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6
votes
1
answer
474
views
Existence of well-ordering of epsilon_0 in weak theories
In a discussion on a youtube video on the hydra game I jokingly mentioned how everyone was assuming that $\varepsilon_0$ was well-ordered. This lead to a bit of disagreement (in a nice way!) about the ...
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