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Hi, I am a string theorist and a publicist.


May
13
revised Why doesn't string theory have a mass gap?
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May
13
answered Why doesn't string theory have a mass gap?
May
13
answered Please justify invoking logical positivism to causal patches and black hole interiors in quantum gravity!
May
13
comment Wavefunction normalization
Could you please specify which "things" are supposed to cancel? The norm surely can't cancel because it is a sum of positively semidefinite terms. Your function is a combination of plane waves so much like a single wave, its normal can't be one. One could normalize similar combinations to a wave function if the $A/B$ ratio were determined as a function of $k$ and if it were continuous. In that case, $|A|^2+|B|^2$ would be normalized exactly in the same way as $|A|^2$ is normalized if there's only one term, one plane wave.
May
13
awarded  Nice Answer
May
12
comment What is the value of the fine structure constant at Planck energy?
Dear @Claude, I assure you that my answer does answer your question. Read the discussion below my answer to catch at least many of the numerous mistakes you are making in your reasoning and which also prevent you from seeing that my answer does answer your question.
May
12
comment What is the value of the fine structure constant at Planck energy?
Dear @Claude, you're confused. The left graph on www-ekp.physik.uni-karlsruhe.de/~deboer/html/Forschung/… shows the standard $U(1)\times SU(2)\times SU(3)$ couplings of the Standard Model I was talking about. None of these three constants ever becomes $1/137$: none of them is the electromagnetic fine-structure constant. The fact that the $U(1)_Y$ coupling in the graph starts at $1/60$ is no mistake while $1/137$ would be mistake. As I explained, you can't extrapolate "the" $1/137$ coupling because it's electromagnetism which breaks down above 100 GeV.
May
12
comment Does the Planck scale imply that spacetime is discrete?
Yes, it does. Even if one could find nearly flat-space solutions in LQG, which no one can (and chances are that it's because there's no flat space in LQG), it would still be true that it would violate the Lorentz invariance much more strongly than the experimental upper bound. The spin networks or, in the path integral language, the spin foam is a (not so) modern version of the 19th century luminiferous aether. It not only violates the Lorentz invariance but also carries a huge entropy density which instantly slows objects much like a dense $10^{95}\,kg/m^3$ "water" slows down swimmers.
May
12
comment Why don't we consider centrifugal force on a mass placed on earth?
Yes, sure, unless you of course buy gold for a million of dollars and using a different weight, they steal $3000 from you. ;-)
May
12
answered What is the extent of Earth's gravitational pull?
May
12
comment Why don't we consider centrifugal force on a mass placed on earth?
Dear @Martin, you're wrong that the variation of $g$ due to the centrifugal force is smaller than the variation of $g$ because of the bulge, which is also caused by the same centrifugal force. Up to a factor of at most 2, they're the same. See physics.stackexchange.com/q/8074
May
12
answered Particle Accelerator Energy and Luminosity
May
11
comment Does de Sitter space admit an asymptotic S-matrix?
Dear lurscher, thanks for your compliment. The set of states that an observer can prepare on the initial slice - or observe on the final slice - is essentially empty. So the restriction is a restriction down to an empty set of data. If you happen to agree, would you agree that your question then loses beef? There are no known accurately defined observables associated with the full de Sitter spacetime. Of course, one may try to predict things "patch-wise", by treating pieces of the de Sitter space as Minkowski-like spaces. But the whole union is a problem.
May
11
revised Does de Sitter space admit an asymptotic S-matrix?
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May
11
comment What is “pure energy” in matter-antimatter annihilation made of?
I think that "pure energy" is used to denote any intermediate state that carries no conserved charges. So a single virtual photon is "pure energy", too. A virtual graviton or their pair would also be "pure energy". "Pure energy" is meant to have the property that it's not hard for other objects to absorb it (or emit it) without changing their character qualitatively. It's like the energy in the sugars or chocolate that you may quickly transform to the energy to run. An extra proton in the state makes the energy "non pure".
May
11
answered Does de Sitter space admit an asymptotic S-matrix?
May
11
comment The Pioneer anomaly finally explained?
These are good developments - although mundane ones - and a good question. I would bet that the explanation is mostly right. It's not quite new - Toth and Turshyev wrote similar things previously, see e.g. popsci.com/pioneeranomaly - I guess that to say the least, these derivations refute the statement that the Pioneer provides us with strong evidence for new physics. ... I am afraid that one needs to be an experienced "engineer" - like the authors - to offer a truly relevant appraisal of the validity of the paper. It looks OK to me, at a superficial resolution.
May
11
reviewed Approve Why is $\frac{dx}{dt}=0$ in this average momentum calculation?
May
11
revised Does the Planck scale imply that spacetime is discrete?
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May
11
answered Does the Planck scale imply that spacetime is discrete?