# What is nonlocality in relativity ?

1. Feb 14, 2016

### jk22

To explain the correlation in a Bell experiments three solution are considered :
1) faster than light communication
2) preexisting values are revealed at each measurement points
3) nonlocality applies

1) is ruled out by relativity
2) is ruled out by Bell's theorem

Remains nonlocality. But what does it mean ?

Is it that in relativity if we go at the speed of light then therr is no space anymore in that reference frame ? Namely if we look at the Lorentz transformation $$x'=\frac {x-vt}{\sqrt {-v^2/c^2}}$$ then v=c is singular.

If we imagine a photon sending a signal from A to B then in its frame all the space between A and B condensate into a single point at infinity since we divide by zero.

This would mean that along A and B in the frame of the phophoton there is no distance hence it were nonlocal and compatible with relativity ?

2. Feb 14, 2016

### A. Neumaier

A photon has no (rest) frame - only massive objects can have one. The signal is sent by massive sources to massive detectors; it only travels (in case of photons) at the speed of light.

This is completely independent of nonlocality issues.

3. Feb 15, 2016

### Demystifier

I would not say that faster than light communication is ruled out by relativity.
First, it is possible that relativity, or more precisely Lorentz invariance, is only an emergent approximative symmetry not valid at the fundamental level.
Second, even if it is fundamental, it is not necessarily in contradiction with faster than light communication:
http://lanl.arxiv.org/abs/1006.1986
http://lanl.arxiv.org/abs/1002.3226