bio  website  math.berkeley.edu/~theojf 

location  Berkeley  
age  29  
visits  member for  4 years, 11 months 
seen  7 hours ago  
stats  profile views  13,998 
I am a recent graduate from UC Berkeley. Starting Fall 2013, I am a Boas Assistant Professor at Northwestern University. My research is broadly centered on quantum field theory — my interests include category theory, representation theory, homological algebra, algebraic topology, Poisson geometry, and theoretical physics.
2d

awarded  Enlightened 
2d

awarded  Nice Answer 
Sep 8 
comment 
Bidual of vector spaces
As @YemonChoi correctly says, without further assumptions you cannot prove the map to be surjective, because it's not true in general. Thus the fact alone that vector spaces form a category is not enough to prove injectivity, since otherwise the proof would apply to the opposite category to prove surjectivity. More damningly, the map can fail to be injective for modules over a ring, so somehow your category needs to "know" that it's over a field to prove injectivity. 
Sep 6 
comment 
Recognize this strange expression from linear algebra?
No offense taken. Sorry about misstating the end. 
Sep 4 
comment 
When is Rep(U_q(g)) invariant under q > q and why?
I don't know if the conventions match yours, but Temperley–Lieb with the circle valued at $\delta = q^2  q^{2}$ is invariant us a monoidal category under $q \mapsto q$ (of course, since the monoidal category only depends on $q$ via $\delta$), and even as a braided category (via the natural isomorphism that acts by $1$ on the defining object), but not as a pivotal category. 
Sep 4 
revised 
Recognize this strange expression from linear algebra?
admitted an error. 
Sep 4 
revised 
Recognize this strange expression from linear algebra?
corrected a 0 to a 2 
Sep 3 
awarded  Enlightened 
Sep 3 
awarded  Nice Answer 
Sep 3 
answered  Recognize this strange expression from linear algebra? 
Sep 2 
comment 
Recognize this strange expression from linear algebra?
@SteveHuntsman Maybe $g_{kl}$ in place of $c_{kl}$? 
Sep 2 
comment 
Are linear algebraic groups rigid?
I don't really know the general definition of "reductive", but is this $G$ reductive "over $k[t]$"? There are many examples of reductive groups degenerating to solvable groups, of which this is a particularly nice one. 
Aug 12 
comment 
Hyperfinite type II_1 factor as the Clifford algebra
I am far from an expert. My impression is that "the hyperfinite II_1 factor" has lots of automorphisms, and different manifestations of it, although isomorphic, often are not canonically isomorphic. The classification of factors only says that a given one is isomorphic to the hyperfinite II_1 factor, and doesn't tell you that they are really "the same" in any meaningful way. But I repeat: I am far from an expert. 
Aug 9 
comment 
What's the state of affairs concerning the identification between quantum group reps at root of unity, and positive energy affine Lie algebra reps?
Great question! I have nothing useful to contribute towards an answer. 
Aug 2 
awarded  Popular Question 
Aug 2 
comment 
String diagrams for bimodules over noncommutative algebras?
@DavidRoberts: Sorry for the slow response. Yes, of course JoyalStreet  I clearly wasn't thinking straight, and went "Street was one of the names ... what's the name that goes with Street?" 
Jul 28 
answered  String diagrams for bimodules over noncommutative algebras? 
Jul 22 
comment 
Removing an article from arxiv
Never use that journal. 
Jul 22 
comment 
When does a monoidal functor between ribbon categories preserve cups and caps, but not necessarily braidings?
Right. The strong monoidal functor from supervector spaces to $(\mathbb Z/2)$modules (with the usual symmetric structure) does not preserve quantum dimension. And any two (right, say) duals are canonically isomorphic, but that isomorphism often is not the identity for some looksconvenient coordinates. 
Jul 14 
comment 
Are there isomeasure simplices?
I assume you are familiar with Schanuel's excellent paper "What is the length of a potato?", but your notion of isomeasure reminded me of it, so in the off chance you don't know that paper, I thought I'd mention it. 