bio | website | |
---|---|---|
location | CHINA | |
age | 27 | |
visits | member for | 2 years, 4 months |
seen | Sep 1 '12 at 9:57 | |
stats | profile views | 62 |
A graduate student.
Apr 5 |
awarded | Yearling |
Aug 29 |
awarded | Supporter |
Aug 29 |
comment |
About Sigma_1 definability
Thank you for your comment! |
Aug 29 |
comment |
About Sigma_1 definability
Thank you so much for your answer, it is very helpful for me. I have been on a travel without internet these days, so it is so late to reply your answer. |
Aug 29 |
accepted | About Sigma_1 definability |
Aug 19 |
awarded | Editor |
Aug 19 |
revised |
About Sigma_1 definability
added 7 characters in body |
Aug 19 |
asked | About Sigma_1 definability |
Aug 4 |
accepted | Definability of the direct limit |
Aug 3 |
comment |
Definability of the direct limit
I just read the remark on iterated HOD classes in your paper. For the iterated ultrapower case, the graph is definable, but this does not happen in iterated HOD case. Thanks for your helpful answer again. |
Aug 3 |
comment |
Definability of the direct limit
Thanks for your kind answer. If the entire system $<M_i|i<\omega>$ and $<j_{i,j}|i<j<\omega>$ are definable, then pick any representation of the direct limit, it is definable. But I still not well understand why the entire system is definable? $<M_i|i<\omega>$ is a sequence of classes, in general, an infinite sequence of classes need not be definable. But I have a feeling this sequence $<M_i|i<\omega>$ is similar to a sequence defined by induction, so whether "a sequence of classes defined by induction" is indeed definable? |
Aug 3 |
asked | Definability of the direct limit |
Jul 21 |
awarded | Nice Question |
Apr 7 |
comment |
A least model contains a given model and a given set
Thanks for your comments. I understand. If M is a proper class, then using closure of Godel's operations, there is a "closure" of $M\cup\{x\}$ as Jech' 13.24, which is an inner model of ZF. But if M is a set, then from the above link answer, such M[x] need not exist. |
Apr 4 |
awarded | Scholar |
Apr 4 |
accepted | A subgroup intersects every conjugacy class |
Apr 4 |
comment |
A subgroup intersects every conjugacy class
The example of upper triangular matrix is so standard, thank you for your example! |
Apr 4 |
comment |
A subgroup intersects every conjugacy class
Thank you for your answer. |
Apr 4 |
asked | A least model contains a given model and a given set |
Apr 4 |
awarded | Student |