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  Is the collapse of the Schrodinger's wavefunction a violation of physics?

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I am in the process of understanding more the wavefunction collapse. I'm told that the interactions to cause a collapse are already included in all the possibilities of Schrodinger's equation so the agent that collapses it, can't be a physical agent and it might be the human mind. All the events are already included as I read about it. What is the flaw with this reasoning? Can another particle interacting with the system be considered an observation? or what collapses the wavefunction can't be a physical agent?

asked May 21 in Theoretical Physics by Paul [ no revision ]
recategorized May 27 by Dilaton

Yes, the collapse of the wave function occurs whenever a measurement/observation is made, which means an interaction between your system and something else. There is nothing non-physical in this process. There is also no need for some conscious being observing the system in order to collapse its wave function.

No physics is violated. Schrödinger's equation only holds for isolated systems, hence cannot apply during measurmeent, where the system measured is not isolated.

The system on which you wish to perform measurements with an apparatus can be enlarged to consider a combined system of system + apparatus. Quantum states can also be considered for this combined system. The system can be enlarged further to include the environment of the apparatus, and in principle also an observer.  The interactions of the subsystems in particular with the environment bring about what is known as local decoherence. The enlarged system remains in a pure quantum state, but this state can be expressed as a linear combination of products of a state of the system with a state of the apparatus with a state of the environment (with a state of the observer). In each such product state, the system is in a particular state, the apparatus is in a specific state indicating the particular state of the system (and the observer may be considered to be in a state of having observed the specific state of the apparatus). 

In such a decoherence scenario there is no collapse of the wavefunction in the original meaning of the concept. There is more an aligning of the states of involved subsystems into mutually consistent combinations, while the total system remains in a pure quantum state. How to "interpret" this is probably beyond strictly physical considerations. 

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