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bio website motls.blogspot.com
location Czech Republic
age 41
visits member for 4 years, 6 months
seen 14 hours ago

Hi, I am a string theorist and a publicist.


14h
comment Polchinski Equation (10.4.7)
Similarly, the OPE you are asking for is not "equal" to zero, but it is $\sim 0$ because the OPEs had no singular terms to start with, so one couldn't have gotten any singular terms by differentiation, either. But again, $b(\sigma_1) \partial_\sigma^7 b(\sigma_1) b(\sigma_2)c(\sigma_2)$ has no reason to be zero, has it?
14h
comment Polchinski Equation (10.4.7)
You are probably confused by the difference between the $=$ sign in the OPEs, and the sim sign $\sim$. The latter indicates that the right hand side only lists the singular terms, i.e. is correct up to additive terms $+O(1)$.
14h
comment Polchinski Equation (10.4.7)
Dear MaPo, the product of the two operators is surely not equal to zero. Just map it to the cylinder, if the plane distracts you. $b(\sigma_1) b(\sigma_2)$ is just a product of two anticommuting operators, right? Why should it be zero? It is $O(z)$ indeed because there's no singularity for $z\to 0$ and the value for $z=0$ is zero due to anticommutation. But for $z\neq 0$, it cannot be zero.
1d
comment Graviton saturation, alternative explanation of galaxy rotation curves?
Magnus, you would need to write some equations. This kind of "spirit" of yours is nice, and probably basically shared by some original minds, but what is missing are the equations - what actually makes the gravity bounded and how? Moreover, what you need is kind of the opposite. You need to make gravity stronger than expected by Newton when the acceleration is too low (MOND) etc. At this vague level, this fixed theory of yours is pretty much "the same thing" as MOND, and if you mean something else, you need to describe it more accurately than you did.
1d
revised Polchinski Equation (10.4.7)
added 629 characters in body
1d
answered Polchinski Equation (10.4.7)
1d
comment Connection between the M5 brane and (2, 0) superconformal field theory
Also, there is no contradiction between the non-existence of a Lagrangian of a full theory, and the existence of a Lagrangian for a dimensionally reduced (compactified, taken to the limit) theory. And yes, the behavior of M5-branes must have some more contrived, bootstrap-like, cubic and higher-order etc. structures that are seeds of those in all of M-theory. There are some hints in the literature, but no complete answer. Each paper about (2,0), and there are lots of them, addresses these questions to one extent or another but there's no known complete answer.
1d
comment Connection between the M5 brane and (2, 0) superconformal field theory
This is a very interesting question with lots of dimensions and subtleties and implicit errors in the question etc. First of all, (2,0) is just the low energy, deep infrared limit of the dynamics of coincident M5-branes, not "everything" about M5-branes in a generic situation. Second, the non-existence of a Lagrangian description is a conjecture, or a claim about the invalidity of the usual simplest Lagrangians we could guess. The problem is with the self-duality of the 3-form.
Jul
16
awarded  Enlightened
Jul
16
awarded  Nice Answer
Jul
15
awarded  Enlightened
Jul
15
awarded  Nice Answer
Jul
14
awarded  Nice Answer
Jun
30
awarded  Enlightened
Jun
30
awarded  Nice Answer
Jun
24
comment meaning of Higgs coupling is flavor conserving
No. Well, the Majorana neutrino masses are typically flavor-violating - they cause flavor-changing oscillations - but those mass terms are usually not considered "parts of the Standard Model" because they must arise from some beyond-the-Standard-Model dynamics as effective terms (they are not gauge-invariant etc. classically). One may talk about the CKM matrix, too - it also changes flavor. But mass terms aren't really "interaction terms", anyway, because they are quadratic.
Jun
24
answered meaning of Higgs coupling is flavor conserving
Jun
21
comment Atomic Physics: stimulated emission
Right, it's a technicality to achieve a given state - and the method isn't necessarily unique. The laser starts to operate when this state is achieved and the laser actually emits.
Jun
21
comment What experiment would disprove string theory?
That's what Polchinski et al. are saying but they are wrong, as shown in numerous papers, like those by Raju and Papadodimas. But this is a way too extensive question that is off-topic in this general thread.
Jun
21
awarded  Nice Answer