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bio website motls.blogspot.com
location Czech Republic
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visits member for 3 years, 3 months
seen 12 hours ago

Hi, I am a string theorist and a publicist.


Feb
4
answered Is $\hat{\phi}^{-}\hat{\phi}^{+}$ a well defined observable in the Quantum field theory of a scalar field?
Feb
4
answered Did relativity make Newtonian mechanics obsolete?
Feb
4
answered Non-Euclidean spaces in Quantum Mechanics
Feb
4
revised Can a very small portion of an ellipse be a parabola?
added 146 characters in body
Feb
4
answered Can a very small portion of an ellipse be a parabola?
Feb
4
answered Schrödinger's cat; why was it necessary?
Feb
4
answered Even-branes in IIA and odd-branes in IIB
Feb
4
comment What does it mean for the Leggett Inequality to falsify realism in general in Quantum Mechanics?
Yes, quantum mechanics rejects the classical notion of realism - while quantum mechanics is compatible with locality and many important QM models, like quantum field theories, imply exact locality. Bell's inequalities rule out local realism but there are many other (and stronger) thought-and-real experiments etc. etc. that rule out huge classes of nonlocal realist theories, too. When taken together, realism is ruled out even without adjectives, and it's been really ruled out at the physics level of rigor for over 85 years. Sadly, too many popular books claim it's "locality" that's ruled out.
Feb
3
awarded  Enlightened
Feb
3
awarded  Nice Answer
Feb
2
comment Does Galileo's Tower of Pisa argument contradict quantum mechanics?
Dear @TerryBollinger, even if we decide not to talk about quantum mechanics - where I think you are misinterpreting the wave function as a classical wave that may be directly probed - I don't understand why you think that Galileo's argument is right; and why it's something else than a claim about the equivalence principle. Do you disagree that one may write down theories where the forces do depend on the density or mass distribution? Do you disagree that the independence on the density/distribution is the same thing as the EP?
Feb
2
comment A dictionary of string - standard physics correspondences
Dear @ArnoldNeumaier, I don't really claim that there are no other entries that you could consider analogous. I just think that it's not clear which entries you would consider analogous and which entries you would not. For example, there is F-theory model building where you can link the gauge group in the spacetime (like E6) with the type of singular fibers in the F-theory. Is that analogous to the counting of generations in heterotic string theory? If it is, we may be forced to include almost every insight/sentence about string phenomenology in thousands of papers, too. ;-)
Feb
2
comment Anomalous target space diffeomorphisms for one-loop world-line integrals
Yes, I think so. The Rindler space is equivalent, by a coordinate transformation, to a part of the Minkowski space but the fact that we are only considering a "part" has implications for the path integral etc. It really means that some boundary conditions in the Rindler space won't be quite well-defined, and one should entangle the Rindler wedge with the other one and discuss the possible entangled states etc., and some of these effects of the "other" Rindler wedge are also linked to the Minkowski space divergence.
Feb
2
comment Does Galileo's Tower of Pisa argument contradict quantum mechanics?
You are probably imposing some unphysical ideas about the quantum waves when you talk about "relative wavelengths" etc. - do you mean some differences or ratios of wavelengths of waves for different objects that manifest themselves in interference experiments? Interference is only possible for two portions of the wave function for the same object. A neutron doesn't interfere with a dineutron, for example. Even spin-up electron doesn't interfere with the spin-down but otherwise the same electron.
Feb
2
comment Does Galileo's Tower of Pisa argument contradict quantum mechanics?
Dear @Terry, dineutrons fail to be stable, by 60 keV, but they do. If you imagine a world where dineutrons form and you measure any interference or any process involving them in a freely falling frame, you will not recognize that you are in a gravitational field. That's what the equivalence principle implies. On one hand, you say that you don't question the EP; on the other hand, you clearly do. I am confused by the sequences of the words. The EP holds even in QM with Earth's uniform gravity and neutrons and all arguments that it doesn't are wrong.
Feb
2
comment What does a $SU(2)$ doublet really mean?
Because the proton and neutron are not identical in the same sense in which the dog and cat and different. However, the proton and neutron are more similar and in many respects (when it comes to the strong nuclear force), they do behave according to identical rules, as opposed to dogs and cats.
Feb
2
comment Does Galileo's Tower of Pisa argument contradict quantum mechanics?
I think that you are noticing that the wavelength depends on the reference frame. Of course it does. It depends in the same wave as the inverse momentum because it's the same thing.
Feb
2
comment Does Galileo's Tower of Pisa argument contradict quantum mechanics?
Sorry, @Terry, I have already tried to correct this error of yours, but you were not listening. The de Broglie wavelength measurement is nothing else than the momentum measurement (and the momentum depends on the reference frame in the obvious way, it's $mv$...). So the person just measures that the momentum of 2 balls is 2 times the momentum of 1 ball. There is no other non-momentum (in particular, "geometric") measurement of the de Broglie wavelength; the phase of the wave function is not observable. Could you please try to read the previous sentence again?
Feb
1
comment Regularization and renomalization in the lightcone quantization of bosonic string
Yes, the scale invariance implies that the beta-function and all conceivable versions or generalizations of it are equal to zero. Yes, scale invariance means that the theory is equally well-defined at all scales, so in particular, it can't have the Landau pole or any other breakdown point. That's also why scale-invariant theories (RG fixed points, in another terminology) are so important to understand both the short-distance and long-distance limits of other theories, and as other limits, they may be extrapolated arbitrarily far.
Feb
1
comment Earth's Temperature
No, Bak, the angle of incidence has nothing to do with the length of the route. The angle is about what direction the Sun is located relatively to the Earth's surface at a given point; the distance is the radial coordinate that isn't encoded in the angles in any way.