bio | website | mathstat.dal.ca/… |
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location | Stockholm, Sweden | |
age | 31 | |
visits | member for | 4 years, 9 months |
seen | yesterday | |
stats | profile views | 2,613 |
math.LO/math.CT, currently postdoc at Stockholm University. Previously Institute for Advanced Study, Princeton, lately of Dalhousie University, Nova Scotia, and Carnegie Mellon University, Pittsburgh.
Jul 29 |
comment |
Do direct limits (filtered colimits) commute with pullbacks, in C*-algebras?
Both at math.se and here, the title was rather unclear, which I think is why there’s been some misunderstanding and negative reactions in comments (including thinking that the question was more trivial than it is). I’ve edited the title to give the actual question a bit more clearly; hopefully I’ve understood OP’s intentions correctly. |
Jul 29 |
revised |
Do direct limits (filtered colimits) commute with pullbacks, in C*-algebras?
Clarified title to give question more specifically |
Jul 25 |
comment |
Why do Lie algebras pop up, from a categorical point of view?
“The category of Lie algebras is equivalent to a certain category of cocommutative Hopf algebras” — do you know a good reference that works this out or states it more precisely? Or at least some specific term which readers can google for more details? |
Jul 21 |
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 4-foot and 3-foot lines, in that case in 5-line stanzas (4 / 3 / 4 / 4 / 3). |
Jul 2 |
awarded | Curious |
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@TimothyChow: while I don't disagree with your points in general, the length restriction in JAMS seems to be no longer current --- looking at recent issues, most have at least one paper of $\geq$ 60pp, and there are even a few around the hundred-page mark.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 J-iterated 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 cardinal-finite, then you can use the indexed-monoidal-product 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 un-compelling — 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 self-dual 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. 3-against-4 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 13-against-14 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 |