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bio website motls.blogspot.com
location Czech Republic
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Hi, I am a string theorist and a publicist.


May
16
revised Incommensurability between different observers describing the same universe?
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May
16
answered Incommensurability between different observers describing the same universe?
May
16
comment Why is it hard to solve the Ising-model in 3D?
One may work on something without knowing some essential insights about those matters that were found in the last 25 years but that doesn't mean that his work may be a world quality work as of 2011. It can't.
May
16
comment Why is it hard to solve the Ising-model in 3D?
Dear @Marek, you have no clue what you're talking about. Non-conformal versions of theories such as the Ising model, when they're integrable, may be shown to be integrable by their being deformations of the conformal theories whose integrability is guaranteed by the conformal symmetry, and the integrability survives after the deformation. See e.g. arxiv.org/abs/hep-th/9312169 and especially its reference 1 by Zamoldchikov and hundreds of other papers about similar issues e.g. scholar.google.com/…
May
16
revised Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
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May
16
comment Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
Moreover, as far as my reading of the critical papers against the CCC goes, none of them articulates why conceptually there can't be any patterns of a similar kind beyond the spectral curve, so they're destined to write new critical papers - and recalculate their things using the full WMAP maps - whenever Penrose and Gurzadyan modify their prescription how to "see" their circles etc. This is really unnecessary. The attempt to find any patterns of this kind using these methods is fundamentally misguided.
May
16
comment Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
Thanks a lot for these words. Robert. I could have made it more comprehensible but it would require lots of optimizations. Yes, people are bounded by so many sociological constraints and groupthink. In fact, one can't even learn that in the privacy of their offices, everyone knows that e.g. these papers by Penrose and Gurzadyan are wrong. But everyone chooses not to say it - because Penrose is a popular and famous chap and no one wants to stand against popular things.
May
16
comment Why do 'dead' batteries work again after exchanging the places of the batteries in an electronic device?
What probably matters most is that you waited for a fwe minutes. A battery can "revive" itself by distributing the material more conveniently. You may think that a nearly dead battery suffers from congestion, hiding some useful material behind the material that is discharged, but it gets cured when you wait for a while.
May
15
reviewed Approve suggested edit on What is the most natural definition of the weak hypercharge coupling constant if grand unification is wrong?
May
15
comment What is an observer in quantum mechanics?
A nice secret way to promote the logic of decoherence without using the word, +1. ;-)
May
15
revised How to define angular momentum in other than three dimensions?
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May
15
revised Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
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May
15
answered How to define angular momentum in other than three dimensions?
May
14
comment Can space-like fields not commute and still forbid faster-than-light signalling?
Well, it's surely possible with fermionic fields that anticommute rather than commute at spacelike separations. Well, even if some fields fail to commute and fail to anticommute, it may still mean that these fields are just nonlocal functionals of some other fields that actually do supercommute (anticommute or commute, depending on statistics) at spacelike separations, in which case superluminal signals are still forbidden.
May
14
comment What is the most natural definition of the weak hypercharge coupling constant if grand unification is wrong?
In the particular case of hypercharge, see en.wikipedia.org/wiki/Hypercharge to get some idea about the values. Quarks and leptons have $Y$ equal to various multiples of $1/3$. Moreover, there exist two comparably frequent conventions on whether $Q=I_3+Y$ or $I_3+Y/2$, adding another ambiguity of a factor of two into the conventions on the normalization of $Y$; in the non-$1/2$ convention, $Y$ is a multiple of $1/6$. What can be measured is e.g. the scattering amplitude of two down-quarks but the coupling constant is just one factor in one term in the total expression.
May
14
comment What is the most natural definition of the weak hypercharge coupling constant if grand unification is wrong?
@Claude: "After all, coupling constants can be measured, so it must be possible to define them uniquely." - Coupling constants may be measured e.g. from the scattering of charged particles with unit charges. But for $U(1)$ gauge groups underlying charges, the "unit" charges are notoriously ambiguous. Even for the electric charge, it's really questionable whether the unit charge is carried by the positron, $+e$, or the down-antiquark, $+e/3$. In more complicated theories with more general spectrum, it becomes even more questionable what is the "unit charge", and therefore "what is $g$", too.
May
14
comment What is the most natural definition of the weak hypercharge coupling constant if grand unification is wrong?
@Claude: "Taking your remark to the extreme, it would mean that normalization of the weak hypercharge is not fixed at all if GUTs are wrong." - There is nothing extreme about this statement. It is totally harmless, innocent, obviously true, and it was the main point that my answer wanted to convey, indeed. You may normalize your fields in any way you want, and if there's no unification-like link between different fields, you may naturally normalize different fields differently, too.
May
14
comment What is an observer in quantum mechanics?
Dear @Isaac, "nobody knows" isn't really an accurate answer. It's more correct to say that we do know that there is no unique answer because the question depends on definition and is associated with no operational way to test it. We talk about observers to express the idea that various properties of physical systems may be "perceived" or measured by some objects, but what is exactly needed for an object to be able to measure "something" with a certain "accuracy" depends on the "something" and the "accuracy", as well as all other details. There is no "universal" answer to all such questions.
May
14
comment Feedback on the paper, 'CCC-predicted low-variance circles in CMB sky and LCDM' by V. G. Gurzadyan and R. Penrose
Thanks, Anna, but your +1 was only at the level of words, not buttons. ;-)
May
14
revised How do you explain spinning tops to a nine year old?
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