Maaneli said:
I've read the first paper before, and I liked it very much. But I still don't understand how you've managed to get around the need for a preferred frame or spacetime foliation.
it does not
http://arxiv.org/PS_cache/quant-ph/pdf/0607/0607124v1.pdf
Since the existence of a time foliation would be against the spirit of relativity, several attempts have been undertaken at obtaining a relativistic Bohm-like theory without a time foliation. I briefly describe four such proposals in this subsection, items (i)–(iv) below. However, (i)–(iii) are not satisfactory theories, and (i) and (iv) both involve some foliation-like structure, something just as much against the spirit of relativity as a time foliation.
(i) Synchronized trajectories [11, 21, 56]. Define a path s 7→ X(s) in (space-time)N as the integral curve of a vector field jψ on (space-time)N, with jψ a suitably defined current vector field obtained from a wave function ψ on (space-time)N. The path
X(s) =(X1(s), . . . ,XN(s)) defines N paths in space-time, parametrized by a joint parameter s, which are supposed to be the particle world lines. This approach is based on a naive replacement of space with space-time. Apparently, it does not possesses any equivariant measure, and thus does not predict any probabilities.
Moreover, it does introduce a foliation-like structure: The joint parametrization defines a synchronization between different world lines, as it defines which point on one world line is simultaneous to a given (spacelike separated) point on a second world line. Indeed, the synchronization is encoded in the world lines since, if N non-synchronous points X1(s1), . . . ,XN(sN) on the N world lines are chosen, then the integral curve s → Y (s) of jψ starting from Y (0) =(X1(s1), . . . ,XN(sN)) will generically lead to different world lines than X.
11.-Berndl, K., Durr, D., Goldstein, S., Zangh`ı, N.: Nonlocality, Lorentz invariance, and Bohmian quantum theory. Phys. Rev.A 53: 2062–2073(1996).
21.-Dewdney, C., Horton, G.: A Non-Local, Lorentz-Invariant, Hidden-Variable Interpretation of Relativistic Quantum Mechanics Based on Particle Trajectories. J. Phys. A: Math. Gen. 34: 9871–9878 (2001).
56.-Nikolic, H.: Relativistic Quantum Mechanics and the Bohmian Interpretation. Foundations of Physics Letters 18: 549–561 (2005).
Foliation independent:
http://arxiv.org/PS_cache/quant-ph/pdf/0607/0607124v1.pdf
The GRW theory can be made relativistic, without a time foliation or any similar structure, when using the flash ontology [72] [74].
The foliation independence of the model can be expressed in the following way: With every spacelike 3-surface epsilon in the future of epsilon
0 there is associated a wave function ψ
epsilon on epsilon
N , the conditional wave function, which depends on all flashes between epsilon
0 and epsilon, as well as on the seed flashes before epsilon
0 and, of course, on the initial wave function. (Indeed,the conditional wave function collapses at every flash.)
.-72 Tumulka, R.: A Relativistic Version of the Ghirardi–Rimini–Weber Model. To appear in J. Statist. Phys. (2006).
.-74 Tumulka, R.: Collapse and Relativity.On the Present Status of Quantum Mechanics, AIP Conference Proceedings 844, 340–352. American Institute of Physics (2006).