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visits member for 3 years, 9 months
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I do not participate on this site any longer, except to respond to comments regarding my own text, if that text is unavailable in another form. I do not accept the political moderation atmosphere here, it is not compatible with open science. Unfortunately, this seems to be a recurring pattern on such sites--- they grow with promises of open participation, and then shut down in a phase transition of censorious moderatorship. Hopefully physicsoverflow.org will be the first exception to this rule, as the policies there were crafted specifically to avoid this phenomenon.


Aug
15
answered Common false beliefs in Physics
Aug
15
comment What is the difference between a measurement and any other interaction in quantum mechanics?
There is a problem with the literature of philsophy--- its mechanisms of peer review are not moderated by neither experimental input nor rigorous proof, so the methods of evaluation are entirely political. The history of thought does not suggest that political competition of ideas without external moderation using experiments or rigor can ever be successful.
Aug
15
comment What is the difference between a measurement and any other interaction in quantum mechanics?
The agent doesn't have to be a person--- it's a sort of disembodied consciousness, and it could even be a collective. This doesn't have any bearing on the issue of whether consciousness is computation because a computer interacting with a quantum system is just as mysterious as a person collapsing the wavefunction. A computer can't compute in quantum mechanics without doing a measurement at the end to see what was computed. If we think the computer somehow has a "sense" of what its memory is, this leads to a collapse of the wavefunction relative to this sense.
Aug
15
answered Is Mach's Principle Wrong?
Aug
15
comment Is causality a formalised concept in physics?
Anixx is not wrong, just taking a nonstandard philosophical path through a certain well-trod thicket.
Aug
15
answered Do all massive bodies emit Hawking radiation?
Aug
15
comment Do all massive bodies emit Hawking radiation?
The charged particle in free fall most certainly does radiate!!
Aug
15
comment What potential energy functions are mostly used in Schrodinger equation?
I added some entry points. The basic theoretical results are that all the energy eigenstates in one and two dimensions with an arbitrarily small random potential decay exponentially at long distances. In three dimensions and higher, there is a phase transition as you vary the strength of the randomness between localized and extended wavefunctions. There is very little known rigorously, as far as I know, but a huge amount known by physics standards of certainty. I added a few very old literature pointers in the answer itself.
Aug
15
revised What potential energy functions are mostly used in Schrodinger equation?
add literature entry points
Aug
14
awarded  Revival
Aug
14
revised Where do the choice of basis in QFT come from?
not markup
Aug
14
answered Where do the choice of basis in QFT come from?
Aug
14
answered What potential energy functions are mostly used in Schrodinger equation?
Aug
14
revised Did Einstein prove $E=mc^2$ correctly?
shorten, remove wikipedia-isms
Aug
14
answered Did Einstein prove $E=mc^2$ correctly?
Aug
14
comment Is this geometrical 'derivation' of Brownian motion legitimate?
I just wanted to add that in mathematics, a process which doesn't go anywhere on average is called a martingale, and this is called the martingale derivation of the sqrt(N) law. I think Levy of Levy flight fame did things like this.
Aug
14
answered Entropy of an empty universe
Aug
14
comment Why is there an absolute entropy?
This is correct, but I think it should be expanded to say that the entropy becomes a number because quantum states in finite volume/energy are discrete, so there is a number of them. In infinite volume, they become extensive but without the fine-graining classical ambiguity.
Aug
14
comment The entropic cost of tying knots in polymers
The unknot is only entropically favorable for short polymers, where you can calculate the entropy brute force, by simulating. For the long polymer limit, where you need a scaling analysis, the unknot would be unlikely. I was going to think about an answer in the long skinny polymer limit.
Aug
14
revised What does it mean that the neutral pion is a mixture of quarks?
explain why this works pretty well