bio  website  dorais.org 

location  Hanover, NH  
age  
visits  member for  4 years, 8 months 
seen  13 mins ago  
stats  profile views  12,970 
I like math and a few other things...
3h

comment 
If questions are formalized as ideals of a boolean algebra, what kind of algebra of questions appears from Stone representation theorem?
This looks very similar to what is often known as "Medvedev's logic of finite problems" in the context of intermediate logics. 
1d

revised 
The (un)decidability of RobinsonArithmeticwithoutMultiplication?
Added the original axiom 1 since it has been edited in the question. 
1d

accepted  The definition of < in Robinson's Q 
1d

comment 
The definition of < in Robinson's Q
Thanks Emil! That makes a lot of sense. I guess everybody is just following the original definition. 
2d

comment 
The definition of < in Robinson's Q
@ChristianRemling: I noticed that too but according to Google books, Burgess actually suggests defining $x \lt y$ as $\exists z(z' + x = y)$. I haven't read the book though, so I'm not sure about the context. 
2d

revised 
The definition of < in Robinson's Q
typos 
2d

revised 
The definition of < in Robinson's Q
edited tags 
2d

asked  The definition of < in Robinson's Q 
Jul 21 
revised 
Mixed integer programming formulation for Ising model
edited tags 
Jul 21 
revised 
proof for unsolved problem
edited tags 
Jul 20 
comment 
Alternative definition of a category
@Bob: I recommend getting a copy of that book, it's a good read. The book is about categories and allegories. Their approach to categories (and allegories) is essentially objectfree. 
Jul 20 
comment 
Alternative definition of a category
See also Categories and Allegories by Freyd and Scedrov. 
Jul 17 
comment 
Embeddings of forcing notions  preserve properness?
An interesting counterexample to $(D4)\Rightarrow(D3)$ is due to Zapletal in On the existence of a $\sigma$closed dense subset MR2741884. Zapletal shows that it is consistent to have two dense subsets $P$ and $Q$ of some poset such that $P$ is $\sigma$closed but $Q$ has no $\sigma$closed dense subset. It's an open question whether the existence of such $P$ and $Q$ is provable in ZFC. 
Jul 16 
revised 
Is it compatible with ZF to assume that every amenable discrete group is finite?
fixed omegas 
Jul 16 
answered  Is it compatible with ZF to assume that every amenable discrete group is finite? 
Jul 16 
comment 
Is quasivariety generated by all perfect graphs finitely axiomatizable?
@AndrásSalamon: Since the $\sigma_k$ are a complete axiomatization, they prove the purported finite axiomatization. Such a proof uses only finitely many of the $\sigma_k$, which together form a complete axiomatization. 
Jul 15 
comment 
If there are two primes at an even distance $k$ is there another disjoint pair of primes also at distance $k$?
No, I was just happy you addressed that flimsy interpretation in your answer! 
Jul 15 
comment 
If there are two primes at an even distance $k$ is there another disjoint pair of primes also at distance $k$?
The question is perhaps poorly worded but as it stands now it only asks that: for every even $k$, there is not exactly one pair of primes at distance $k$ from each other. Though unusual, I find that question interesting too. 
Jul 14 
revised 
Is every set class generic over a given inner model?
for searching 
Jul 8 
comment 
Does V=L imply transitive containment over, say, Z?
Most formulations of $V = L$ make transitive containment redundant. Whether you use the Gödel $L_\alpha$, Jensen $J_\alpha$ or other hierarchies, these are transitive by design so formal statements for V = L, like $\forall x \exists \alpha (Ord(\alpha) \land x \in L_\alpha)$, immediately imply transitive containment. Transitive closure is a bit tricky but it often follows too. 