96,937 reputation
7128265
bio website motls.blogspot.com
location Czech Republic
age 40
visits member for 3 years, 6 months
seen 46 mins ago

Hi, I am a string theorist and a publicist.


Mar
29
comment Weakly gauge a symmetry?
Dear MBN, the wine from Israel I received as a gift after a (not only) physics talk/discussion in the Prague Jewish Community may have sped things up a bit - I've drunk about 0.4 liters tonight because it tasted nicely. :-) I must have (innocently) said many offensive things but the term "igelit" that the Czechs use for all soft plastics, even though it is nothing else than the trademark of IG Farben, a German corporation that employed 80,000 slaves in Auschwitz and possessed the Zyklon B patent, is probably a faux pas to remember. :-) Time for bed now.
Mar
29
comment Weakly gauge a symmetry?
Thanks, and please try to consider the key point of the paper, in Figure 1, a map claiming that the Czech Republic is an oasis of a relatively rational thinking inside the swampland of the European Union that promotes things such as the catastrophic man-made global warming. ;-)
Mar
29
revised Weakly gauge a symmetry?
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Mar
29
comment Weakly gauge a symmetry?
No prob, cortana, I do have enough of it, so please don't feel any urge to return and upvote. ;-) By the way, by accepting the answer, you gave more "credit" than by an upvote. ... Nima Arkani-Hamed et al. would be using this technique all the time and I often listened to their discussions and talks (not to speak about papers). ... I updated and extended th answer a few times, so you may try to reload and check whether it's more informative than before.
Mar
29
revised Weakly gauge a symmetry?
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Mar
29
answered Weakly gauge a symmetry?
Mar
29
revised Weak equivalence principle tests
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Mar
29
revised Weak equivalence principle tests
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Mar
29
comment Weak equivalence principle tests
He did an extremely good job in squeezing it in - otherwise it wouldn't survive, indeed... It was very reasonable for you to consider the possibility that it's some serious stuff - but the fingerprints are way too obvious for those who have been pleased to receive similar creative comments by Uncle Al on their physics blogs. ;-)
Mar
29
answered Weak equivalence principle tests
Mar
29
revised Size of atoms based on atomic number
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Mar
29
comment If the Sun were to suddenly become a black hole of the same mass, what would the orbital periods of the planets be?
The equivalence of the gravitational fields would hold exactly in general relativity, too - because of Birkhoff's theorem, en.wikipedia.org/wiki/Birkhoff%27s_theorem_(relativity) - As long as there is no gravitating source "outside the Sun" or "outside the black hole", the outer portion of the solution has to be given by the Schwarzschild metric, and the mass parameter of its solution was guaranteed to be the same - and this mass is measured at infinity, too. So the changes inside the Sun are irrelevant outside it.
Mar
29
answered Distance in cosmology
Mar
29
comment formal framework for talking about 'minimal couplings'
I forgot to add a pedagogic comment for extremely slow readers: this question and the corresponding answer has nothing whatsoever to do with experiments. It's about the explanation of a word used while constructing theories. With minimal couplings, one may construct both experimentally valid and experimentally invalid theories. However, if a theory has the right field content, the minimal coupling (among those preserving the desired symmetries) is extremely unlikely to have a zero coefficient, and as long as it is nonzero, it dominates the long-distance physics.
Mar
29
awarded  particle-physics
Mar
28
answered formal framework for talking about 'minimal couplings'
Mar
28
answered Size of atoms based on atomic number
Mar
28
comment Chemical potential
And yes, of course, in relativity, the bounds are obviously such that in the non-relativistic limit, you reduce the relativistic statistical physics to the non-relativistic one. There's also a question about the convention for the shift of $E$ and $\mu$, whether $mc^2$ is included in them. In the most natural choice where one counts the whole energy including $mc^2$, bosons have $\mu< +mc^2$, which is the relativistic translation of $\mu<0$, but $\mu> -mc^2$ must also hold (antiparticles...).
Mar
28
comment Chemical potential
Dear Anirbit, my language was ambiguous a bit. I didn't mean the word "because" as explaining the difference between bosons and fermions. The "because" sentence was purely about fermions, and for fermions, both things are needed: $N_i$ never exceeds 1 - I was assuming that everyone knows that Pauli's principle holds for fermions, otherwise he should avoid difficult topics such as bounds on their chemical potential - and one also needs the number of states to be finite because otherwise, one could get a divergent overall $N$ of the fermions from a large number of boxes, despite $N_i\leq 1$.
Mar
28
comment What does this observation of instantaneous velocity in Brownian particles mean?
Right, I agree, except that I don't see this point in your answer. ;-)