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Coelum

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- Is energy conserved (not in a statistical sense) during a measurement in QM?

Dear PFer's,

this is a problem I have been struggling with for years. Is energy conserved (not in a statistical sense) in QM? The so-called collapse of the wavefunction, occurring during a measurement process, is incompatible with energy conservation - at least in the general case. A starting point for the discussion is Sean Carrol's paper with the same title as this post (https://arxiv.org/abs/2101.11052). In Carroll's classification, I favour the idea that our description is not complete, though not in the sense of some "hidden variable" theory but rather as an incomplete description of the measurement process itself.

As a side note, I understand that, on a cosmological level, energy is not conserved. Both the non-zero value of the cosmological constant and the time asymmetry in the history of our universe show it is not. I just wonder if we can somehow recover the energy conservation at a more "local" level, like we do in Classical Mechanics thanks to Noether's theorem.

I'd really appreciate your point of view.

this is a problem I have been struggling with for years. Is energy conserved (not in a statistical sense) in QM? The so-called collapse of the wavefunction, occurring during a measurement process, is incompatible with energy conservation - at least in the general case. A starting point for the discussion is Sean Carrol's paper with the same title as this post (https://arxiv.org/abs/2101.11052). In Carroll's classification, I favour the idea that our description is not complete, though not in the sense of some "hidden variable" theory but rather as an incomplete description of the measurement process itself.

As a side note, I understand that, on a cosmological level, energy is not conserved. Both the non-zero value of the cosmological constant and the time asymmetry in the history of our universe show it is not. I just wonder if we can somehow recover the energy conservation at a more "local" level, like we do in Classical Mechanics thanks to Noether's theorem.

I'd really appreciate your point of view.