Singular cardinals and strong extenders

[bibtex key=ApterCummingsHamkins2013:SingularCardinalsAndStrongExtenders]

Brent Cody asked the question whether the situation can arise that one has an elementary embedding j:VM witnessing the θ-strongness of a cardinal κ, but where θ is regular in M and singular in V.

In this article, we investigate the various circumstances in which this does and does not happen, the circumstances under which there exist a singular cardinal μ and a short (κ,μ)-extender E witnessing “κ is μ-strong”, such that μ is singular in Ult(V,E).

Large cardinals with few measures

[bibtex key=ApterCummingsHamkins2006:LargeCardinalsWithFewMeasures]

We show, assuming the consistency of one measurable cardinal, that it is consistent for there to be exactly κ+ many normal measures on the least measurable cardinal κ. This answers a question of Stewart Baldwin. The methods generalize to higher cardinals, showing that the number of λ-strong compactness or λ-supercompactness measures on Pκ(λ) can be exactly λ+, if λ>κ is a regular cardinal. We conclude with a list of open questions. Our proofs use a critical observation due to James Cummings.