bio | website | colorado.edu/math |
---|---|---|
location | Boulder, CO | |
age | 32 | |
visits | member for | 4 years, 9 months |
seen | 2 days ago | |
stats | profile views | 559 |
I am a math instructor at the University of Colorado at Boulder. My interests have evolved from proof theory and philosophical concerns about knowledge to the upper reaches of set theory and the large cardinal hierarchy. I also occasionally dabble in combinatorics of the finite sort.
Jan 2 |
comment |
A question on rank-to-rank embeddings
I'm a little confused by the remark on Skolem functions. Do you have an example of a total Skolem function $f$ whose image $j(f)$ is partial? Is your worry that such functions won't be total in general, or do you have a specific set A and/or a formula $\varphi$ in mind? |
Jul 2 |
awarded | Curious |
Jun 11 |
comment |
Are normal ultrafilters generated by conditional closure systems?
@JDH: If I'm thinking of the correct "Solovay's lemma" that was mentioned, I think there is a nice proof at Andres Caicedo's blog. |
Jun 10 |
accepted | Stationary sets in HOD |
Jun 10 |
comment |
Stationary sets in HOD
Right. That was sloppy of me. I'll need to think about your great answer some more. In the meantime, I guess I'm trying to articulate a question about the definability (not necessarily using only ordinal parameters) of clubs and stationary sets. |
Jun 10 |
comment |
Stationary sets in HOD
@JDH. Thank you for your answer. One interesting fact that I glean from it is that stationary sets are definable, whereas there are club sets that are not not (at least from ordinal parameters). Is this correct? Since you mention the forcing which kills a stationary/co-stationary set, is this the only way to conclude that there are club sets which are not definable, or is there an easier argument to see this? |
Jun 10 |
asked | Stationary sets in HOD |
May 20 |
awarded | Fanatic |
Feb 25 |
accepted | Elementary Embeddings and Relative Constructibility |
Feb 16 |
comment |
Antichains and the Knaster Property
@Paul McKenney: Thanks for your comment. I posed the question because I had a deep misunderstanding of the concept and you alerted me to this fact. Thanks! |
Feb 16 |
revised |
Antichains and the Knaster Property
The background of the question was false and made for a confusing question. |
Feb 13 |
revised |
Ultrapowers of ultrapowers
added set theory tag |
Feb 13 |
suggested | approved edit on Ultrapowers of ultrapowers |
Feb 13 |
accepted | Antichains and the Knaster Property |
Feb 13 |
comment |
Antichains and the Knaster Property
@MohammadGolshani: Yes, thank you!. I've edited my question. |
Feb 13 |
revised |
Antichains and the Knaster Property
switched the ordering of my question to make sense |
Feb 13 |
asked | Antichains and the Knaster Property |
Feb 2 |
comment |
What is the definition of a large cardinal axiom?
@Joel and Asaf: given your comments, how would you alter any of the proposed categories? I'm certainly willing to give up the full strength of ZFC, but I'm really not familiar enough with many of its fragments and their respective strength. Is ZFC or its strengthenings simply too strong a base to use when attempting a definition of "large cardinal"? |
Feb 2 |
answered | What is the definition of a large cardinal axiom? |
Jan 24 |
comment |
What is the definition of a large cardinal axiom?
@StevenLandsburg: Couldn't it move toward a consensus? Sites like this provide a deeper and at the same time broader understanding of topics informed by experts working in the field, even if that understanding borders on what might be considered more philosophical concerns. If the only "definitions" of large cardinal are implicitly understood, so be it. But certainly we could benefit from having a single source collecting together some of these implicit "definitions", right? |