62,212 reputation
489211
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location New York City
age 41
visits member for 3 years, 11 months
seen 11 hours ago

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
19
comment Why is cold fusion considered bogus?
-1 This answer is ignorant of calorimetry. The effect Pons and Fleischmann observed was energy output at 30% above the light-water control, many many sigma above their (calibrated) calorimetric error, sporadic in time, and lasting too long to be chemistry. Unless you believe that heavy water is magic, any storage and release of energy must be stored in the Pd electrode, and is restricted to 1eV per atom in a gram of Pd, a bound which was exceeded many times over. These explanations are so foolish, it is irresponsible to repeat them.
Aug
18
answered Why is cold fusion considered bogus?
Aug
18
comment Why should the Standard Model be renormalizable?
The standard model is a well defined mathematical object--- it's a theory without neutrino masses. It may be wrong experimentally, but its renormalizable.
Aug
18
comment Why should the Standard Model be renormalizable?
-1 --- The standard model is certainly renormalizable, 'tHooft proved it. I have spoken to some people who lived through the era, and at least a few of them understood very well that if they find a renormalizable theory, then it would be valid up to essentially arbitrarily high scales, perhaps up to the Planck length. This was a major motivation for finding a renormalizable theory.
Aug
18
comment Do all massive bodies emit Hawking radiation?
I didn't say no horizon means no radiation--- I said if there is stuff between you and the horizon, you see the stuff, not the emissions from the far-away virtual horizon. The virtual black hole business is silly--- a virtual black holes can pop in and pop out, but it conserves energy and doesn't lead to any detectible particle production unless there is a horizon visible. Every static solution has a conserved energy.
Aug
18
comment How come random matrices can predict energy spectra of heavy atoms?
This is just folklore from the 90s. That an integrable system has no level repulsion is an ancient result, probably known to Bohr/Sommerfeld/Einstein. There's a nice review of the Gutzwiller trace formula here: teorfys.uu.se/files/Martin_Lubcke_gutz.pdf. Here is a review of scarring, focusing on the predicted corrections to random matrix theory:xxx.lanl.gov/pdf/chao-dyn/9810013v1. The basic answer I give is more elementary than the corrections, and is found in the early pages of this book: books.google.com/books?hl=en&lr=&id=oo03LoIDYQsC
Aug
18
comment a priori validity of $W=\int Fdx$ in relativity?
Also, in skimming over the paper, he does say that this quantity must be the work done, because it must equal the gain in electrostatic potential energy along the integration path. This is the thermodynamic a-priori argument I was talking about.
Aug
18
comment a priori validity of $W=\int Fdx$ in relativity?
What I am saying is that the notion of force which can be seen to have the property that $W = \int F dx$ is whatever mechanical quantity that appears on the left hand side of "F=qE" in relativity (where the right hand side is just the spatial gradient of the electrostatic potential, without any velocity factors). Einstein figures out this quantity in his special relativity paper by transforming from a frame moving along with the particle.
Aug
18
comment a priori validity of $W=\int Fdx$ in relativity?
I don't think that the four-force is "wrong", just wrong for generalizing the horribly non-covariant expression $\int F dx$. I personally am more comfortable with four-force, which is why I asked myself the exact same question "why does Einstein consider this formulat obvious?" many years ago.
Aug
18
revised a priori validity of $W=\int Fdx$ in relativity?
clear up that its potential energy that is independent of velocity
Aug
18
answered a priori validity of $W=\int Fdx$ in relativity?
Aug
17
answered Why does the air flow faster over the top of an airfoil?
Aug
17
answered Does the wavelength always decrease in a medium?
Aug
17
answered Deriving Newton's Third Law from homogeneity of Space
Aug
17
comment Why can we treat quantum scattering problems as time-independent?
@Marek--- the critics are right, and your description is not even a good way of describing the time-dependent case.
Aug
17
comment Why can we treat quantum scattering problems as time-independent?
-1 This answer is no good. You are turning off the scattering potential at $t=-\infty$ for no reason, the Hamiltonian in a scattering problem of the sort the OP is asking about is time independent. The answer is ridiculously formal, and all the interesting things are in the "it can be shown...".
Aug
17
awarded  Necromancer
Aug
17
comment Why isn't there a centre of charge?
-1 This answer is totally wrong. The acceleration of a rigid sphere E in response to point/sphere source S is exactly the same as the response of a point mass to the same sphere/point source. The reason is that the point and the sphere make the same outside potential, so a point E and a sphere E have exactly the same reaction force on S, therefore they must feel the same action force from S. There is no way around it. Tidal forces come from shape distortion, like oceans rising and falling, not from the rigid spherical shape.
Aug
16
comment Common false beliefs in Physics
The "glass is a slow fluid" thing is not really fair--- this is derived from an old controversy, only recently understood, over whether an amorphous glass transition is actually sharp, or whether it is a rounded smooth non-phase-transition. It was plausible to believe that it wasn't sharp before recently, so that liquid and solid glass are not separated by a melting transition.
Aug
16
comment Common false beliefs in Physics
Points 3 and 5 are false. Electrons move fast in a metal (although not as fast as the field), and it is completely possible for the trace point of an oscilloscope to move faster than light.