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seen Nov 10 '11 at 18:49

Feb
22
comment Spinning Tachyons
I agree with Lubos too. ;)
Feb
21
comment Spinning Tachyons
@truebeliever Have a look at the following paper and papers that cite it. As I recall, some of what they found in this paper was later reinterpreted by Sen&Zwiebach in terms of decay of unstable D-branes. The stuff on Lorentz violation probably involves an uncontrolled approximation and as far as I know has not been backed up by later studies. Still, the idea is intersting. Spontaneous Breaking of Lorentz Symmetry in String Theory. V.Alan Kostelecky, (Indiana U.) , Stuart Samuel, (City Coll., N.Y.) . IUHET-139, CCNY-HEP-88/4, May 1988. 8pp. Published in Phys.Rev.D39:683,1989.
Feb
21
comment Spinning Tachyons
Is it clear that this must be true in string theory with an infinite tower of spin one and higher spin states? There have been speculations about Lorentz violation appearing in Open String Field Theory through condensation of vector states, but I don't think any computations have shown that this actually happens in a well controlled approximation.
Feb
18
comment What restricts the value of weak hypercharge from being 5/3?
@Carl No thank you to me is needed. I guess you could thank physics stackexchange though. I know at Math Overflow they have a protocol for citing the site.
Feb
17
comment Why should the mass of leptons to be near of proton and QCD/chiral scales?
The electron is massless in the SM before gauge symmetry breaking and then acquires a mass proportional to a Yukawa coupling and the Higgs vev. You can't just ignore this and start talking about E&M self-energy. You're discussing the QFT of the 1930's.
Feb
16
comment Are neutrinos Majorana particles?
This is a pretty confusing and/or deceptive quote because as Lubos explains, you can give masses to neutrinos in a very simple way with a slight extension of the Standard Model. It doesn't require extra dimensions. Not sure what they mean by the "sacred distinction" between matter and anti-matter. We already know both C and CP are violated. The only thing sacred is CPT and you certainly don't need CPT violation to explain neutrino masses either.
Feb
16
comment Scale dependence of energy dissipation in viscous flow via AdS/CFT
Thanks @Daniel Grumiller. Those references look very helpful.
Feb
16
comment Scale dependence of energy dissipation in viscous flow via AdS/CFT
This answer sounds physically plausible, but I don't see how to relate it to what people actually calculate. In the calculations of the viscosity I have looked at there is no mention of quasinormal modes. One works in Lorentzian signature and imposes boundary conditions at the horizon that only allow incoming modes, that is absorption of the perturbation. Perhaps there is a more complete physical description that includes some of what you say in this answer but this more complete description is not needed to compute the viscosity.
Feb
15
comment Scale dependence of energy dissipation in viscous flow via AdS/CFT
My local hydro guru says the simplest picture is the obvious one of large scale motion turning into heat which is a flow from large scales to small scale microscopic motion, but there are more complicated possibilities which arise in 2d turbulence, in flows in a pipe and so on. So it is not clear to me what to make of the AdS/CFT picture I described. Perhaps someone who has worked on this will eventually show up and have something more useful to say.
Feb
15
comment Scale dependence of energy dissipation in viscous flow via AdS/CFT
I've read about the Kolmogorov description of turbulent flow, but as @Moshe mentioned, I don't understand why we are in the turbulent regime in this problem. What length scale am I supposed to use to define the Reynolds number?
Feb
12
comment What are the alternatives to the Higgs mechanism?
You asked for "all" not "best". There are many alternatives to the simplest model: 2 Higgs fields, 3 Higgs fields ad infinitum; technicolor models; Susy models, top condensate models, little Higgs, Higgsless and so on and so on with hundreds of papers on each topic. This is way too broad a question to expect a short useful answer.
Feb
12
comment What are the alternatives to the Higgs mechanism?
The FAQ says "ask practical, answerable questions based on actual problems that you face." Does your question fit this criterion?
Feb
8
comment Why is there a deep mysterious relation between string theory and number theory, elliptic curves, $E_8$ and the Monster group?
I still think a more specific question would be better, but I can see that there might be some interesting and useful answers so I've voted to reopen.
Feb
7
comment Is there any physics that cannot be expressed in terms of Lagrange equations?
This is pretty much a duplicate of the question cited by Moshe, vote to close as a duplicate.
Feb
7
comment Bosonic M-theory and moonshine gravity
There is a lot of interesting numerology mentioned here but I have a hard time following the logic.
Feb
7
comment Why is there a deep mysterious relation between string theory and number theory, elliptic curves, $E_8$ and the Monster group?
There are lots of interesting and appropriate questions involving these topics but this broad "why" question is not going to get any kind of reasonable answer. I'd suggest you reword the question to make it a more specific question about some aspect of these relations that you are interested in.
Feb
5
comment Vector product in 2 dimensions
This is not a physics question.
Feb
5
comment $N=4$ supersymmetric yang-mills theory and S-duality
No, but it is the best way. ;)
Feb
4
comment $N=4$ supersymmetric yang-mills theory and S-duality
For A. do you really have trouble looking this up in the literature? The simple way to derive it yourself is via dimensional reduction of N=1 SYM in d=10. B. seems more like a demand than a question. Same for C.
Feb
4
comment Lattice QCD and string theory
I'm afraid the answer is that anonymous posters on blogs are not the most reliable source of information.