Yuji

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As an occupation, I'm a mathematical physicist, studying string theory and quantum field theory.

I've developed as a hobby a few Cocoa (Touch) apps. The largest one so far is spires.app, which manages articles and metadata downloaded from the arXiv eprint server, the inspire database, and the journal websites.

I'm also interested in many other things, which is why I ask questions in various StackExchange sites ...

	1,522 reputation	bio	website	member.ipmu.jp/yuji.tachikawa	visits	member for	2 years, 3 months
413 badges		location			seen	May 13 at 9:11

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Jan 17	comment	Construction of the supersymmetric Faraday tensor @QuantumDot Read Wess-Bagger. The answer is there.
Nov 3	comment	Is there a theorem that says that QFT reduces to QM in a suitable limit? A theorem similar to Ehrenfest's theorem? @Prathyush Ask as a separate question. That's how stackexchange works.
Jul 16	comment	About 2+1 dimensional superconformal algebra Now that you understand that point, I think you should stop asking and think for several days by yourself. Good luck!
Jul 16	comment	About 2+1 dimensional superconformal algebra You need to distinguish two questions: what is the representation of the supercharge and what is the representation of the quantum states the supercharge is acting on. In order to get the inequality you're interested, you need to consider the latter question. You can't fix $I$ to be $N\times N$ and $M_{\mu\nu}$ to be $2\times 2$. They depend on $h$ and $j$. You try extracting $j$ from the $M_{\mu\nu}$ you already fixed, but that's not the point. $j$ depends on the quantum states.
Jul 14	comment	About 2+1 dimensional superconformal algebra 2) Right. 3) The author didn't say Gamma are all real, he just said sigma is real. 4) You need to understand that the matrices M are determined by j and that the metrices $I$ are detemined by h.
Jul 14	comment	About 2+1 dimensional superconformal algebra 1) The right matrices to use depend on the quantum states. What you wrote down is not OK even in a single superconformal multiplet. How did you determine which matrix representations of SO(N) and SO(2,1) to use?
Jan 2	comment	General Relativity research and QFT in curved spacetime @Kyle: That's also an interesting subject, but I meant this type of things: arxiv.org/abs/0905.4352
Dec 29	comment	Wilson/Polyakov loops in Weinberg's QFT books I don't know if it's in it or not (look for "area law" or "confinement" in it). Note that you and I may think this topic as classic, but I guess it can be too modern a topic for him. Anyway, just stop regarding his book as sacred.
Dec 16	comment	On the Coulomb branch of N=2 supersymmetric gauge theory Well, anything which was done in the last century should be considered basic. The SUSY textbook by Terning covers basic stuffs pretty well.
Dec 15	comment	On the Coulomb branch of N=2 supersymmetric gauge theory There's a reason why textbooks and papers are called differently:) I say, you should just try reading a paper which interests you most, using various references. If you can, then you're ready; if you can't, then you're not.
Dec 12	comment	On the Coulomb branch of N=2 supersymmetric gauge theory Once you finish a basic QFT textbook and a SUSY textbook, just pick whatever recent paper which motivates you most, and try to understand it. The required materials are either in the review sections or in the references in the paper. Going through it line-by-line won't work, because the author didn't intend the paper to be read that way. Rather, try to work out an example which is slightly different from what's dealt in the paper. That way, you'll learn exactly which tools are necessary, which part of the paper can be improved, and once done, it might result in your paper!
Dec 11	comment	On the Coulomb branch of N=2 supersymmetric gauge theory Which topic are you referring to? Chiral rings? This paper arxiv.org/abs/hep-th/0211170 contains a nice review. In general, read and understand all papers by Seiberg or by Witten. Problem solved.
Nov 19	comment	“finite” QFTs and short-distance singularities and vanishing beta functions @Anirbit , even in free field theory there's a loop integral which diverges: i.e. a one-loop diagram without any vertex. This corresponds to the zero-point energy of free oscillators, which makes the partition function diverge in the UV. So, your points 1,2,3 already apply to the theory of one free boson, and are always there.
Nov 18	comment	“finite” QFTs and short-distance singularities and vanishing beta functions Please rephrase your question. Even a theory of free bosons $\phi$ has a short distance singularity in its two-point function $\langle \phi(x)\phi(y)\rangle$.
Nov 3	comment	How to prove quantum N=4 Super-Yang-Mills is superconformal? Your argument is definitely nicer :)
Oct 28	comment	Miura transform for W-algebras of exceptional type By improving the program now the expression is about ~0.9MB :)
Oct 27	comment	Miura transform for W-algebras of exceptional type Thanks, I managed to get the generators. The degree-9 one was not so bad; but the degree-12 one, when dumped to a file, has ~ 100MB as an expression. Oh Buddha.
Oct 26	comment	Miura transform for W-algebras of exceptional type Thanks everyone; I know got the generators at degree 2 and 5. Now I need those at degree 6, 8, 9 and 12 :p
Oct 26	comment	Miura transform for W-algebras of exceptional type Yes you're right. Physicists cover their lack of deep thinking by lots of explicit calculation:p I've been using that approach to find generators of W(E6), but that's still quite messy. That's why I asked the question here.
Oct 26	comment	Miura transform for W-algebras of exceptional type Thank you, but my main problem is to explicitly write down the subalgebra commuting with the screening operators. For A and D, it's done by Fateev-Zamolodchikov and Fateev-Lukyanov. Their forms are quite useful because it can be readily implemented in a computer algebra system. I just want to perform a few stupid calculation inside W-algebra of type E6, but I first need to realize it inside computer.