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May
24
revised Gravimagnetic monopole and General relativity
added 1130 characters in body
May
24
answered Gravimagnetic monopole and General relativity
May
24
comment Wigner-Eckart projection theorem
Right, it's usual to write a vector in the middle of the reduced matrix element but because it doesn't matter on the components, it's the same as if you write any component over there.
May
23
revised Wigner-Eckart projection theorem
added 45 characters in body
May
23
answered Wigner-Eckart projection theorem
May
23
comment Is a 125 GeV Higgs large (or small) for the MSSM?
Right, I would probably join those who guess that the particular sentence in the article is just wrong. MSSM surely prefers "naturally" smaller values than 125 GeV, such as those "slightly above" the Z-boson mass only.
May
23
answered Is a 125 GeV Higgs large (or small) for the MSSM?
May
23
comment How do you explain spinning tops to a nine year old?
Funny, I would call her a brunnette. ;-) You must be from a nation South from mine, right? ;-)
May
23
comment Commutators and Hermiticity - Exam question
Right, that's the situation I started with. A Hermitian $A$ similar to $J_z$ is the easier subclass of solutions. On the other hand, $B$ has absolutely no reason to be Hermitian here which is why it may be a thing such as $J_+$.
May
23
comment Derivation of the supergravity action in 11D
It's exactly the same condition. One looks for the most general 11D field content and action that has exactly 2 derivatives in each term - the presence of a fermion is counted as 1/2 of a derivative (square root as a derivative) and a fundamental boson such as the metric tensor or a gauge potential is dimensionless. If you require 11D supersymmetry of such a theory, the 11D SUGRA action is the unique solution up to field redefinitions. One may prove those things starting from the free spectrum and adding interactions, motls.blogspot.com/2012/04/royal-status-of-11-dimensional.html
May
22
awarded  Nice Answer
May
22
reviewed Approve Does Gödel preclude a workable ToE?
May
22
revised Reference for the ${\cal N}=3$ Chern-Simons Lagrangian at general $N_c$, $N_f$
added 397 characters in body
May
22
answered Reference for the ${\cal N}=3$ Chern-Simons Lagrangian at general $N_c$, $N_f$
May
22
revised Radiative Corrections and Bremsstrahlung
added 184 characters in body
May
22
revised Radiative Corrections and Bremsstrahlung
added 863 characters in body
May
22
answered Radiative Corrections and Bremsstrahlung
May
22
comment How to get Planck length
Let me just mention that those of us who have actually studied the subject – after the equivalent of those 1,000 pages and maybe a bit earlier – not only know that classical GR becomes invalid near the Planck scale, which one understands from page 3, but we also have a working knowledge of the actual correct physics that replaces it. I don't quite understand the logic of "arguing against" my proofs organized by someone who not only confesses not to have the knowledge of those 1,000 pages – but who seems boldly ignorant even about the "first three pages" of introductions to the subject.
May
22
comment Quantum Entanglement - Measuring Twice
Dear Karsus, indeed, by the same reasoning, $j_x$ cannot change, either. By rotational invariance, the behavior of $j_x$ and $j_z$ is obviously the same behavior. And indeed, it doesn't change. When you measure $j_x$ twice, you get the same result. If you measure $j_x$ and then $j_z$, the probability of $j_z=+1/2$ is 50% just like that of $j_z=-1/2$ after the first measurement. And $j_z$ doesn't change between the two measurements; the second measurement just determines which answer was right. The terminology of a "collapse" is always misleading. There is no "collapse" as a real process.
May
22
comment How to get Planck length
There is obviously no string theory used on page 3; string theory is being explained on the remaining 1,000+ pages of the two volumes of the book. The first pages of the book are a basic introduction to the scales at which classical general relativity breaks down because it collects quantum corrections (which are uncontrollable via field theory methods because the theory would be non-renormalizable which proves that there must be new physics at that scale, as Polchinski argues).