This account is temporarily suspended to cool down. The suspension period ends on Aug 24 at 17:32.
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475176
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location New York City
age 40
visits member for 2 years, 8 months
seen 7 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.


Jun
26
revised On-shell symmetry from a path integral point of view
remove brackets
Jun
26
revised On-shell symmetry from a path integral point of view
rolled back to a previous revision
Jun
25
comment The necessity of the B field
@LarryHarson: I was talking about the 1905 paper, where he just knows that E and B exist. But the derivation can be made using only the fact that q is independent of frame. If E were a gradient of a scalar, so that there were no B, then q would have to transform like mass under boost. If E were the gradient of a metric tensor, like in GR, again, q would have to transform. This how Purcell gets the general form, although I don't like it so much. There are only a discrete set of tensorial covariant expressions that match the low energy limit, and it's not wrong to select one based on experience.
Jun
25
revised If we know the universe is made up of a relativistic ether, why wouldn't gravity just be a pressure gradient of the ether?
fix stupidities
Jun
24
comment The necessity of the B field
@LarryHarson: Under the assumption of covariance, the special case at low velocities implies the general thing: once you know the behavior at slow speeds, you find the behavior at high speeds by boosting. How do you find the correct covariant behavior quickly? You find a convariant expression which reduces to the correct nonrelativistic limit, in this case it's uniquely determined, from the tensor form of F, which follows from the invariance of charge under boosts. This is how you derive the second equation from the special case of the first, and it is how Einstein did so.
Jun
22
comment How does electricity flow in conductor when potential difference is applied?
@SatwikPasani: Because the current is constant, and the voltage adjusts itself quickly so that the heat production from the current matches the potential drop--- it's the only self-consistent solution, and it's set up when you close the circuit at the speed of light. The distribution of charges doesn't change the voltage difference across the battery, because this is determined by the chemical reactions in the battery, this is the initial driver to set up the voltage differences in the wire.
Jun
21
awarded  Nice Answer
Jun
20
comment How can we be sure that nature isn't “faking” quantum statistics?
@user834: That's not a compromise. Factoring takes exponential resources by some simple rule of thumb estimates on the number of bits "eaten up" by multiplication.
Jun
20
awarded  Necromancer
Jun
19
awarded  Revival
Jun
19
comment How to prove that proper orthochronous Lorentz transformations form a group?
@Nicolo': Yes .
Jun
18
comment How to prove that proper orthochronous Lorentz transformations form a group?
That's the definition of the Lorentz group, I don't know what there is to prove.
Jun
12
awarded  Enlightened
Jun
12
awarded  Nice Answer
Jun
11
awarded  quantum-gravity
Jun
6
awarded  Nice Answer
Jun
3
comment Have we figured out how to analyze turbulent fluids?
@cspirou: Sure they do, but computers are only fast enough to do Reynolds numbers of order 100, while fully developed turbulence is Reynold no infinity. There's more statistical structure there, you shouldn't have to make the computer work so hard.
Jun
3
comment Have we figured out how to analyze turbulent fluids?
@PeterShor: It's a part of AdS/CFT related to the membrane paradigm. Any quantum field theory in a thermal state has fluid flows when you perturb it generically (the thermal state breaks conformal invariance, and so you end up with normal Navier Stokes with dissipative friction). So the long-wavelength deformations of a particular fluid are mappable one-to-one to deformations of a black hole. This was exploited by several people a few years ago to find some properties of black holes, but there is a chance for back-insights from gravity to turbulence, the gravity end is completely different.
Jun
3
awarded  Necromancer
May
31
revised Have we figured out how to analyze turbulent fluids?
date