980 reputation
514
bio website
location
age
visits member for 2 years, 2 months
seen Aug 3 at 22:00

Feb
24
comment Gauge fermions versus gauge bosons
Josh is saying that "fermionic gauge particle" would be a more applicable name. To answer your question: this is disallowed by local quantum field theory. Look up the spin-statistics theorem in Weinberg or Srednicki.
Feb
17
comment Does $c = 0$ implies that the theory is “empty”?
Do you mean to restrict yourself to even dimensions? In odd dimensions there is no conformal anomaly.
Feb
13
comment Timelike Shell Collapsing into a Black Hole
I think you're right, and that the EOM for $R$ becomes the geodesic equation for the particles on the shell in the limit where the rest mass of the shell goes to zero.
Jan
30
comment Do primary fields (in a CFT) satisfy the wave equation?
I was the original downvoter, because I thought you were saying that an operator with weight $(h,0)$ doesn't satisfy the wave equation (your answer suggests that $(0,0)$ is the only possibility). I removed my downvote because I understand that wasn't your intention.
Jan
30
comment Do primary fields (in a CFT) satisfy the wave equation?
JP gets kind of lax in volume 2 with the normal ordering notation, and I took that as permission to do the same.
Jan
30
comment Do primary fields (in a CFT) satisfy the wave equation?
Sure, that's fine.
Dec
25
comment S-Matrix in $\mathcal{N}=4$ Super-Yang Mills
From what I understand, the S-matrix for $N=4$ is IR-divergent, as expected for any CFT, but there are some terms in it that are IR-finite and can be unambiguously computed. I would elaborate but that's where my "knowledge" ends.
Dec
23
comment Normalizability of the Hartle-Hawking state in Liouville theory
Hi Trimok, I agree that $<W(\ell_1)W(\ell_2)\rangle$ is the propagator in the "string field theory," but I think it also has an interpretation as the Hartle Hawking wavefunction on the worldsheet. This is easy to see from its definition (3.86). If we insert $W(\ell)$ into the path integral then we are creating a curve on the boundary with length $\ell$, so the path integral $\langle W(\ell_1)W(\ell_2)\rangle$ just computes the integral over all manifolds whose boundary is two circles of length $\ell_1,\ell_2$. This is $\Psi_{\text{HH}}(\ell_1,\ell_2)$ by definition.
Nov
22
comment Counting D0-D4 Bound States
Thanks @Ryan! This is very helpful. One minor correction: I think you meant (1-q)^(-8) for the bosonic counting instead of (1-q)^(8).
Nov
7
comment Why do three dimensional gauge theories flow to conformal theories in the infrared?
Oh, I see what you were saying, David. I guess you meant that Luty, Polchinski, and Ratazzi can throw away their assumption of scale implies conformal, since this is now proven. Thats interesting, thanks!
Nov
6
comment Why do three dimensional gauge theories flow to conformal theories in the infrared?
No, they prove that if you look at any field theory (massless or not) at high enough or low enough energies, then it looks like a CFT. This is what I mean by UV and IR.
Nov
6
comment Why do three dimensional gauge theories flow to conformal theories in the infrared?
I know that Dymarsky et al also had a paper on that, but isn't that a different result? It seems to me that that doesn't constrain the RG flow of a general field theory, it just looks at scale invariant theories.
Nov
6
comment Why do three dimensional gauge theories flow to conformal theories in the infrared?
You're right about the dimensionality and Lorentz invariance, I edited this in. It doesn't have to be weak coupling, as long as you assume that scale invariance implies conformal invariance. It doesn't have to be massless, and it's almost always not.
Nov
6
comment Why do three dimensional gauge theories flow to conformal theories in the infrared?
(To clarify, it is the assumptions that are weak and not the authors.)
Nov
5
comment Ghosts on Torus worldsheet
It would be hard to explain it better than chapter 5 of Polchinski. I would recommend that to you.
Aug
23
comment Generalisations of AdS/CFT with string theory on both sides
Why do you say that T-duality is holographic?
Aug
2
comment How are low energy effective actions derived in string theory?
That's right, the two are equivalent. I think you should be able to understand the effective action by reading Polchinski, but that paper by Callan etc. might help also.
Aug
1
comment Mass of empty AdS$_5$
You sure would, and it's in fact done in that paper.
Jul
31
comment Mass of empty AdS$_5$
Your expression is correct, see Balasubramanian and Kraus arxiv.org/abs/hep-th/9902121. @MattReece your argument would hold in Poincare coordinates, but AdS in global coordinates is dual to a CFT on $S^3\times R$. This has a vacuum energy from the Casimir effect, as explained in the above reference. This is familiar from 2d CFT, where the Hamiltonian on the cylinder is the dilatation operator plus a shift proportional to the central charge.
Jul
31
comment How are low energy effective actions derived in string theory?
You just have to compute a lot of string amplitudes, which Polchinski doesn't want to waste time doing. Some of these are left as exercises. Once you've done this you can look for an effective field theory that reproduces the amplitudes, and you'll find supergravity. Alternatively, once you've convinced yourself that string theory preserves spacetime supersymmetry, you know from the fact that there aren't very many consistent supergravity theories that you're going to get the right answer.