# Hardy's Theorem

https://perimeterinstitute.ca/psi_portal/sites/perimeterinstitute.ca.psi_portal/files/hardyphysrevlett.68.2981.pdf

Some researchers in Bohmian Mechanics have hoped to make the theory Lorentz Invariant by modifying our notions of causality in some way or another. I have wondered if this is even possible, and I came to the paper linked. I'm trying to make some sense of the paper. Does his result show that Lorentz Invariance is incompatible with Bohmian Mechanics, even if we modified our notions of causality?

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You might be more likely to get an answer if you add a description of the main result of the paper. This isn't my field, so I don't know what Hardy's Theorem is, or if it is even something people would know by name. I may try to read through the paper later and see if I can answer your question. – Colin McFaul Jul 13 '12 at 1:56
"Therefore it is not possible to reproduce quantum mechanics with a realistic theory in which elements of reality corresponding to Lorentz-invariant observables are themselves Lorentz invariant." This is the main result in the author's words. I know one author who claims to have found a way to make Bohmian Mechanics Lorentz Invariant by modifying our notions of causality. This paper by Hardy seems to make that untenable. – user7348 Jul 14 '12 at 16:51