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bio website motls.blogspot.com
location Czech Republic
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visits member for 3 years, 8 months
seen 15 hours ago

Hi, I am a string theorist and a publicist.


May
7
revised Why is there a minus sign in this wave equation derivation?
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May
7
revised Why is there a minus sign in this wave equation derivation?
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May
7
comment Why is there a minus sign in this wave equation derivation?
Dear Fabian, you're wrong. None of these signs except for one depends on conventions. See my answer.
May
7
answered Why is there a minus sign in this wave equation derivation?
May
7
revised Laplace's equation
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May
7
answered Laplace's equation
May
7
revised Seiberg Witten theory
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May
7
comment Seiberg Witten theory
It was a pleasure. Moduli spaces always share the fact that they're scalars - but they appear in very many very different physical manifestations. The scalar fields may parameterize moduli spaces of spacetime fields in unrealistic theories; spacetime itself that may be a moduli space on the world sheets or world volumes or boundaries in CFT; or the moduli spaces of instanton-like solutions or shapes of Riemann surfaces that have to be integrated over, and so on. In all cases, there are some scalars and their kinetic terms give the metric.
May
7
answered Seiberg Witten theory
May
6
comment Why aren't all rocks in space orbiting bigger rocks?
OK, David, I disagree that you have captured the main point. The OP was asking about small bodies orbiting 100-kilogram bodies. You know that this is impossible and has nothing to do with the 3 details you wrote. The gravitational acceleration coming from 100-kilogram objects is so tiny that the orbital speed would have to be essentially zero for a reasonable radius comparable to 1 AU or similar solar-system-like distances, or smaller. 100 kilograms is $10^{22}$ times lighter than the Earth, so the required orbital velocities for the same $r$ are $10^{11}$ times lower.
May
6
answered Ohm's Law and Space-Charge Limited Current
May
6
comment Gravitational wave energy
Dear Michael, I have already answered this question. A single quantum always carries $E=h\nu$ but the total energy or frequency of a gravitational wave from a binary system has nothing whatsoever to do with that. The predominant - really only possible - wavelength of a binary system is $\lambda = c / \nu$ (universal for all waves!) where $\nu=1/T$ where $T$ is just the period of the orbiting. It would be one year, 365.2422 days, for the Sun-Earth system. The orbital period is different for different binary systems but it can't be derived just from the laws of physics. Got it?
May
6
answered Tunneling Rate Constant
May
6
answered Physical interpretation of equation for relativistic aberration
May
5
answered What is the fastest process or shortest time in nature?
May
5
answered Can you use a laser to measure the speed of light with a rotating mirror?
May
5
comment Why is the angle of the wake of a duck constant?
Interesting, Gerben, don't you think that 19 degrees is falsified by the pictures? Why doesn't your formula depend on the speed of the paddling? Or is the duck's speed kind of synchronized with the phase velocity? If that's how ducks work, it's fascinating and you should surely post it as a competing answer.
May
5
comment Why is the angle of the wake of a duck constant?
Whoops, now it looks like $c_{\rm phase} \sim T \sim 1/f$ instead in which case my "proof" would be totally wrong.
May
5
revised Why is the angle of the wake of a duck constant?
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May
5
comment Why is the angle of the wake of a duck constant?
It was a pleasure.