According to a theorem due to Kenneth Kunen, under ZFC, there is no ordinal and non-trivial elementary embedding $j:V_{\lambda+2}\to V_{\lambda+2}$. His proof relied on the Axiom of Choice (AC), and no proof from ZF alone has been discovered. is the assertion, introduced by W. Hugh Woodin, that is an ordinal and there is an elementary embedding with critical point . And asserts that holds for some . The axiom is one of the strongest large cardinals not known to be inconsistent with AC. It is usually studied assuming ZFC in the full universe (in which case must be a limit ordinal), but we assume only ZF. We prove, assuming ZF + + “ is an even ordinal”, that there is a proper class transitive inner model containing and satisfying ZF + + “there is an elementary embedding ”; in fact we will have $k\subseteq jjI_{0,\lambda}M$. This result was first proved by the author under the added assumption that exists; Gabe Goldberg noticed that this extra assumption was unnecessary. If also is a limit ordinal and -DC holds in , then the model will also satisfy -DC. We show that ZFC + “ is even” + implies exists for every , but if consistent, this theory does not imply exists.

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