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Tim Campion
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Recall that a cardinal $\kappa$ is $(\lambda,\infty)$-almost-strongly-compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\mu$ -- weakly inaccessible with the tree property

  • $\kappa$ -- a $(\mu^+,\infty)$-strongly-compact cardinal

  • every regular $\nu \in [\mu, \kappa)$ -- has the tree property.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

If $\kappa$ can be taken to be $(\mu,\infty)$-strongly-compact, that might be good enough for what I need. Also it should suffice for only the successor cardinals in $(\mu,\kappa)$ to have the tree property.

I apologize for the repeated changes to the question.

Recall that a cardinal $\kappa$ is $(\lambda,\infty)$-almost-strongly-compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\mu$ -- weakly inaccessible with the tree property

  • $\kappa$ -- a $(\mu^+,\infty)$-strongly-compact cardinal

  • every regular $\nu \in [\mu, \kappa)$ -- has the tree property.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

If $\kappa$ can be taken to be $(\mu,\infty)$-strongly-compact, that might be good enough for what I need.

I apologize for the repeated changes to the question.

Recall that a cardinal $\kappa$ is $(\lambda,\infty)$-almost-strongly-compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\mu$ -- weakly inaccessible with the tree property

  • $\kappa$ -- a $(\mu^+,\infty)$-strongly-compact cardinal

  • every regular $\nu \in [\mu, \kappa)$ -- has the tree property.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

If $\kappa$ can be taken to be $(\mu,\infty)$-strongly-compact, that might be good enough for what I need. Also it should suffice for only the successor cardinals in $(\mu,\kappa)$ to have the tree property.

I apologize for the repeated changes to the question.

added 223 characters in body; edited title
Source Link
Tim Campion
  • 64k
  • 13
  • 143
  • 384

Can an almost strongly compact cardinalthere be the successor of a successor cardinalsegment of regular cardinals with the tree property capped by an almost-strongly-compact?

Recall that a cardinal $\kappa$ is almost strongly compact$(\lambda,\infty)$-almost-strongly-compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter for any $\lambda < \kappa$. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\nu$$\mu$ -- weakly inaccessible with the tree property

  • $\nu^+$$\kappa$ - also has the tree property- a $(\mu^+,\infty)$-strongly-compact cardinal

  • $\nu^{++}$ every regular $\nu \in [\mu, \kappa)$ - almost strongly compact- has the tree property.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

If $\kappa$ can be taken to be $(\mu,\infty)$-strongly-compact, that might be good enough for allwhat I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is noneed. But I'm having trouble tracking down even that information

I apologize for the repeated changes to the question.

Can an almost strongly compact cardinal be the successor of a successor cardinal with the tree property?

Recall that a cardinal $\kappa$ is almost strongly compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter for any $\lambda < \kappa$. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\nu$ - weakly inaccessible with the tree property

  • $\nu^+$ - also has the tree property

  • $\nu^{++}$ - almost strongly compact

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

Can there be a segment of regular cardinals with the tree property capped by an almost-strongly-compact?

Recall that a cardinal $\kappa$ is $(\lambda,\infty)$-almost-strongly-compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\mu$ -- weakly inaccessible with the tree property

  • $\kappa$ -- a $(\mu^+,\infty)$-strongly-compact cardinal

  • every regular $\nu \in [\mu, \kappa)$ -- has the tree property.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

If $\kappa$ can be taken to be $(\mu,\infty)$-strongly-compact, that might be good enough for what I need.

I apologize for the repeated changes to the question.

added 30 characters in body; edited title
Source Link
Tim Campion
  • 64k
  • 13
  • 143
  • 384

Can an almost strongly compact cardinal be the successor of a successor cardinal with the tree property?

Recall that a cardinal $\kappa$ is almost strongly compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter for any $\lambda < \kappa$. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can there be a cardinal $\mu$ with the tree property such that $\mu^+$ is almost strongly compactfollowing constellation occur? Ideally $\mu$ would be at least weakly inaccessible.

  • $\nu$ - weakly inaccessible with the tree property

  • $\nu^+$ - also has the tree property

  • $\nu^{++}$ - almost strongly compact

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

Can an almost strongly compact cardinal be the successor of a cardinal with the tree property?

Recall that a cardinal $\kappa$ is almost strongly compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter for any $\lambda < \kappa$. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can there be a cardinal $\mu$ with the tree property such that $\mu^+$ is almost strongly compact? Ideally $\mu$ would be at least weakly inaccessible.

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

Can an almost strongly compact cardinal be the successor of a successor cardinal with the tree property?

Recall that a cardinal $\kappa$ is almost strongly compact if every $\kappa$-complete filter can be refined to a $\lambda$-complete ultrafilter for any $\lambda < \kappa$. A cardinal $\mu$ has the tree property if every $\mu$-sized tree with $\mu$-small levels has a branch of length $\mu$. (If in addition $\mu$ is inaccessible then $\mu$ is weakly compact.)

Question: Can the following constellation occur?

  • $\nu$ - weakly inaccessible with the tree property

  • $\nu^+$ - also has the tree property

  • $\nu^{++}$ - almost strongly compact

I suspect this would be too good to be true. But I don't know much -- for all I know, maybe almost strong compactness implies inaccessibility, in which case of course the answer is no. But I'm having trouble tracking down even that information.

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Tim Campion
  • 64k
  • 13
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  • 384
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Source Link
Tim Campion
  • 64k
  • 13
  • 143
  • 384
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