bio  website  mathstat.dal.ca/… 

location  Halifax, Canada  
age  31  
visits  member for  4 years, 7 months 
seen  yesterday  
stats  profile views  2,570 
math.LO/math.CT, currently at the Institute for Advanced Study, Princeton, lately of Dalhousie University, Nova Scotia, and Carnegie Mellon University, Pittsburgh.
2d

comment 
Rediscovery of lost mathematics
@hobbs: it reminds me nicely of Lewis Carroll’s long but charming Phantasmagoria, which also uses a mixed pattern of 4foot and 3foot lines, in that case in 5line stanzas (4 / 3 / 4 / 4 / 3). 
Jul 2 
awarded  Curious 
Jun 30 
comment 
What is semantics of “type”? Do “types” of “type theory” semantically differ from “set” of set theory?
@YemonChoi: thanks, fixed! 
Jun 30 
comment 
What is semantics of “type”? Do “types” of “type theory” semantically differ from “set” of set theory?
I think this question would be bettersuited to math.stackexchange.com — it’s a fairly introductory question on the subject. If you reask it there, and ping me by replying to this comment, I’ll answer it there. Very roughly, though: the types of computer science correspond not so much to the type theories of Russell, Quine, etc., but more to the type theories of Curry, Church, etc — e.g. the simplytyped lambdacalculus — and there is lots of mathematical work on these systems and their semantics. 
May 9 
comment 
Does Grothendieck have any pseudonymous paper?
@quid: it is certainly sensationalist, but in what way is it vague? The criterion for answers seems quite clear: publicly available work that does not carry Grothendieck's name, but which there's some reason to believe that Grothendieck may have written. 
May 2 
comment 
Submitting a companion paper with detailed proofs ?
@TimothyChow: while I don't disagree with your points in general, the length restriction in JAMS seems to be no longer current  looking at recent issues, most have at least one paper of $\geq$ 60pp, and there are even a few around the hundredpage mark. 
Apr 29 
answered  Generalizing indexed coproduct from $\mathrm{Set}$ to other monoidal categories 
Apr 29 
comment 
Generalizing indexed coproduct from $\mathrm{Set}$ to other monoidal categories
@BrentYorgey: you say in the first comment that you don't want to use the "pick some ordering of J, then use this to take the Jiterated monoidal product" approach, because you're working in a constructive setting. However, what definition of "finite" are you using for J? In such settings there are several options for this? If you assume that J is cardinalfinite, then you can use the indexedmonoidalproduct approach without difficulty. In fact, I may expand this into an answer. 
Apr 20 
comment 
Have axioms / axiom schemata of this flavour been proposed or otherwise considered?
@user18921: I guess it’s that I find your classification rather uncompelling — particularly the suggestion that “more complicated sets from less” axioms tend to satisfy uniqueness properties, while “bigger from smaller” tend not to. 
Apr 20 
comment 
Have axioms / axiom schemata of this flavour been proposed or otherwise considered?
You set up uniqueness as part of the distinction, but in the examples you give of type (2) (Union and Powerset), the sets asserted are unique; and one of your examples for (1), Replacement, is often given in a equivalent form (Collection) which does not satisfy uniqueness. 
Apr 19 
comment 
For which Millennium Problems does undecidable > true?
@ChristianRemling: “The truth of a conjecture can’t make a set $\Pi^0_1$ if it wasn't so to start with.” Sure, but the $\Pi^0_1$ness of a set can be implied by (or even equivalent to) some conjecture. A proof of the conjecture can’t change whether the set is $\Pi^0_1$, but it can tell us whether or not it is. 
Apr 7 
revised 
Why is a braided left autonomous category also right autonomous?
expanded answer, attempted to fix latex, added disclaimer for unfixed parts. 
Apr 7 
answered  Why is a braided left autonomous category also right autonomous? 
Mar 28 
revised 
On the Complement of a subgroup
fixed link (and grammar) 
Mar 10 
reviewed  Approve suggested edit on selfdual representations 
Mar 8 
comment 
Intuitive crutches for higher dimensional thinking
@KConrad: your joke reminds me of a musical version I witnessed. Most musicians have at some point learned to play triplets against duplets — one of your hands plays 2 evenly spaced notes per beat, the other hand plays 3. 3against4 is also not uncommon, and in ≥C20th music, higher divisions also occur. At this particular dinner, one pianist marvelled that another could play a perfectly even 13against14 rhythm; a composer present was surprised at the surprise. “But it’s easy, isn’t it? You just set up one hand playing 13, and the other playing 14, and then you put them together!” 
Mar 8 
awarded  Notable Question 
Feb 25 
comment 
Historical quotation search: Equations/formulae in (Latin?) prose, before modern symbolic notation
@PietroMajer: that’s fascinating! Can you suggest any good sources for seeing the intermediate stages? Or, even better, any articles about this transition? 
Feb 25 
accepted  Historical quotation search: Equations/formulae in (Latin?) prose, before modern symbolic notation 
Feb 24 
revised 
Historical quotation search: Equations/formulae in (Latin?) prose, before modern symbolic notation
added link to this question at the HoM Area 51 proposal 