Recent content by Delta Kilo

https://www.sciencedirect.com/science/article/abs/pii/S0921452699015306

Well, let's just agree to disagree. I still think that "instantaneous update of wavefunction in spacelike separated regions" is a proverbial perfectly rigid rod in Minkowski space. It does not exist, it is an oxymoron. And "nothing to see here, move along" attitude is not going to help solve...

That's only in NRQM, presumably not in QFT, there is no such thing as "instantly". I'm specifically considering relativistic setting here. I'm pretty sure I've seen something along these lines, but I won't be able to provide a reference. I'm sorry for that. If you feel that post was not...

Yes it does take another entangled degree for a ride and carry it around but it does not travel faster than ##c##. This is not exactly standard QM. There are two assumptions: first, that relativistic quantum theory can be locally approximated by standard QM in small enough neighbourhoods of...

I'm not at all put off by randomness and abruptness. There are plenty of sources of randomness and chaos in classical theory already. And the role of environment should not be underestimated. Penrose gave this example: even if we knew exact coordinates and momenta of all particles in a parcel of...

Well, yes. Until the wavefront of environmental decoherence reaches you, you remain unaware. That follows from MWI + relativity. No, it's not like that. Measurement at A is perfectly real for an observer at A from the moment the measurement is done and it remains real and does not change. It is...

Which specific implementation do you have in mind? There are some "ostrich" interpretations where pretty much nothing is real, not sure how it helps. -- The Great Collapsing Hrung Disaster of Gal./Sid./Year 03758 which wiped out all the old Praxibetel communities on Betelgeuse VII is shrouded in...

Thinking about measurements in context of QFT and MWI, I believe there is a way to consistently handle entangled measurements with no spooky actions. Consider typical Bell test. There is a diamond arrangement OABC with 2 particles (say photons) starting at O, measured at spacelike separated A...

For the QM it is defined in a usual way, as per postulates, as the "R" process of wavefunction reduction whereupon wavefunction collapses into one of the eigenstates of observable operator, as opposed to "U" process of unitary evolution. For example this is from Griffiths: Other people like...

Looking at the section 4.3 in the paper I linked at the start of the thread. I'm still trying to figure out exactly what is going on there but looks like they are trying to reduce QFT problem to "already solved" QM. In case of multiple measurements they choose (random) causal ordering of...

Well it has to fit somewhere. Sweeping measurements under the rug sort of works as long as all your measurements are asymptotically far away in the past or in the future and you don't care what happens before initial preparation or after final measurement. Granted, most applications of QM and...

Yes, they both transform under rotation of coordinate system in a consistent way, but according to different rules, SO(3) for vectors and SU(2) for spinors. The angle between vector in 3D space and spin direction remains the same, although spinor acquires a factor ot -1 when rotated by 360 degrees.

Yes, thank you. I was going to read it, after I saw a follow-up: Maximal violation of the Bell-Clauser-Horne-Shimony-Holt inequality via bumpified Haar wavelets (I learned a new word: bumpification :smile:) From Summers' paper: That QFT predicts the same maximal Bell violation as QM is good to...

Hello, I'm interested in how measurement, entanglement, bell test etc are handled in QFT. It seems most QFT texts are being quite light on details on the subject. There would be is a preparation step as the start followed by some interaction and a measurement at the end. Interaction is usually...

There is logical fallacy here. Like, a trajectory of a falling stone can be explained using traditional Newton's gravity without any regard to GR at all. However one theory has spooky actions at a distance and the other does not. Same here, NRQM is manifestly non-local while QFT may be treated...