Recent content by Riposte

Thanks, I think I get it now. In the terminology of Peskin/Schroeder we have: eZ1 = e0 Z2 Z3^(1/2), e'Z1' = e0 Z2' Z3^(1/2), for two particles with the same bare charge. The Ward identity forces Z1 = Z2 and Z1' = Z2', and therefore the two must have the same physical charge as well

For two particles which have identical physical charges (say under electromagnetism), are the bare charges necessarily the same? Since the physical charge is related to the bare charge by photon and particle renormalization factors, I don't see how this could be the case in general. In some...

Wrong interaction term? What do you mean by this? I agree, if you have interactions which turn adiabatically on and off, then there's no problem. However, that's usually not the case. No, what I meant by calling the free vacuum non-physical is that once interactions are added to the...

Sorry, I didn't make myself clear. The Fock space would still be constructed in the usual way. The only difference is how the free vacuum transforms under Poincare transformations: Before, we have U(\Lambda)|0\rangle = |0\rangle Now, we would some non-trivial transformation...

My understanding of Haag's theorem (see link below) is that there is a mismatch between the Hilbert spaces of free and interacting particles. The argument seems to be that we require both the free and interacting vacuum states to be invariant under Poincare transformations. Now since the...

I recently learned about the Many Worlds Interpretation of quantum mechanics from another post on this forum. Unfortunately, the post became more of an argument about whether some experiment had or hadn't proven this interpretation to be true, and there wasn't a whole lot of information on what...

This isn't quite right. In SR, everything's relative. One frame can not be said to be moving faster or slower than another. From the spaceship's frame, time is moving slower both ahead and behind it. From a planet's frame (as the spaceship goes whizzing by) time is moving slower on the...

Oops, my bad. Is there any way to remove this thread?

I agree. I have no problem with the concept of gravitational time dilation. My complaint is that this experiment does not demonstrate/prove what it claims to. I am surprised to hear this. I admit, my knowledge of GR has come only from physics books for the layman. (I will be taking a GR...

First off, the thought experiment made no mention of the equivalence principle. Now, while I agree with your logic, that if an acceleration produces a redshift, then gravity must produce one also, I don't think that has been shown here. The redshift in this experiment does not come...

I thought of a better argument against this experiment. If this experiment were performed in a uniform gravitational field, the result would still be the same. The floor clock would still see blue-shifted pulses (the ceiling clock got a slight headstart, and with a uniform gravitational field...

This brain teaser involves an evil prison warden with way too much time on his hands: 4 men are in thrown in prison for jaywalking. It must have been very blatant jaywalking, for their sentence is 80 years. Luckily for them, the warden is apparently not too attached to his job, because he...

Since both ends are open to air pressure, the only thing that can make water flow through the tube is a difference in heights. Only when the output nozzle is lower than the flask water level will the water flow. This is not the case in the drawing, and what will really happen is that the water...

The classic picture of light is as an electromagnetic wave. In textbooks you get the nice pictures of eletric and magnetic field vectors bound together at right angles, oscillating on into the distance. However, this is a very one dimensional picture. The electric and magnetic fields would...

I recently finished reading Kip Thorne's Black Holes and Time Warps. In it, he proposes a thought experiment (which he attributes to Einstein) which demonstrates gravitational time dilation. I completely disagree with his conclusion and would like to know where I've gone wrong. Here's the...