bio | website | ims.nju.edu.cn/~yuliang |
---|---|---|
location | China | |
age | ||
visits | member for | 3 years, 5 months |
seen | 10 hours ago | |
stats | profile views | 784 |
A mathematical logician.
Jul 24 |
comment |
The (global) theory of Borel equivalence relations
At least the Louveau-Velickovic's result implies the $\Sigma_1$-theory of $(\mathcal{B},\leq_B)$ is decidable. |
Jul 23 |
answered | Are lightface \Delta-1-1 classes of reals describable with hyperarthmetic formulae? |
Jul 23 |
comment |
Are lightface \Delta-1-1 classes of reals describable with hyperarthmetic formulae?
This is a reformulation of the well known result due to Kleene which says that every $\Delta^1_1$ set of reals has a recursive Borel code. The details can be found either in Moschovakis book or Thm 2.7.2 in my joint book with CT. |
Jul 20 |
answered | Borel Sets in Sacks Generic Extension |
Jul 8 |
comment |
Decomposing $\mathbf{\Pi}^1_1$ sets into closed sets
Dilip had a similar idea to Paul's. I think the direct method should work. A further question is whether every Borel set can be decomposed into $\aleph_1$ many disjoint closed sets? |
Jul 8 |
accepted | Decomposing $\mathbf{\Pi}^1_1$ sets into closed sets |
Jul 2 |
awarded | Curious |
Jul 1 |
comment |
Martin-Löf randomness relative to a $\Delta^0_2$-representation of a real
If $x$ is random and $\geq_T \emptyset'$, then any low for $x$ real is $GL_1$. |
Jun 18 |
awarded | Revival |
Jun 18 |
answered | Martin-Löf randomness relative to a $\Delta^0_2$-representation of a real |
Jun 10 |
comment |
Higher recursion theory and reverse mathematics: What is to $\Pi^1_1-CA_0$ as $RCA_0$ is to $ACA_0$?
@Denis, good idea. But when you talk about induction, you need a well ordering. My vague ideal is that infinitary logic might be a right way to make this sense. |
Jun 5 |
revised |
A “suitably generic” set of Cohen reals without forcing?
added 13 characters in body |
Jun 4 |
revised |
A “suitably generic” set of Cohen reals without forcing?
added 157 characters in body |
Jun 4 |
answered | A “suitably generic” set of Cohen reals without forcing? |
May 28 |
accepted | Demuth's theorem in set theory |
May 27 |
revised |
Demuth's theorem in set theory
edited body |
May 27 |
revised |
Demuth's theorem in set theory
added 1042 characters in body |
May 26 |
comment |
Martin's cone theorem and recursion theory
I would like to add a remark that it can be shown that the base is not second order arithmetic definable. |
May 26 |
revised |
Demuth's theorem in set theory
edited title |
May 26 |
comment |
Demuth's theorem in set theory
I was just kidding. Thanks for pointing out this. |