Does Quantum Mechanics Suggest Violations of Conservation Laws?

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Discussion Overview

The discussion revolves around the implications of quantum mechanics (QM) on the conservation laws, particularly the conservation of energy. Participants explore whether the uncertainty principle (HUP) allows for violations of these fundamental laws and the nature of energy conservation in quantum systems.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant suggests that due to the HUP, only expectation values can be discussed, implying that energy conservation might allow for instances of violation that cannot be measured.
  • Another participant counters that all matrix elements of an operator can be measured, indicating that if energy conservation were truly violated, it would have been observed.
  • A third participant questions the understanding of energy conservation in QM, stating that systems do not necessarily have precise energy, which complicates the notion of conservation in this context.
  • It is noted that the HUP is an inequality related to the dispersions of measured expectation values, and the interpretation of energy-time uncertainty is less clear than that of position-momentum uncertainty.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the HUP for energy conservation, with no consensus reached on whether violations of conservation laws can occur in QM.

Contextual Notes

The discussion highlights limitations in the interpretation of energy conservation in quantum systems, particularly regarding the role of expectation values and the nature of measurement in QM.

pivoxa15
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In QM only expectation values can be discussed due to the HUP. i.e energy conservation implies the change in the average value of energy with time is 0. So does that mean there are instances where fundalmental physical laws like the conservation of energy are violated? But we will never be able to measure these violated instances due to the HUP?
 
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Generally all matrix elements of an operator can be measured, not just expectation values. If conservation of energy were violated, it could be observed, but it hasn't been.
 
pivoxa15, are you sure you know what you mean when you are talking about conserving or not conserving energy? The system doesn't necessarely have any precise energy, so I don't understand what it could mean, that the energy is not conserved then.

To my understanding, the conservation of expectation values is as far as the conservation laws go in quantum physics.
 
To be precise the HUP is an inequality about the dispersions in measured expectation values of two operators. Time is not an operator in QM so the interpretation of the E-t HUP is not that clear as the position-momentum one.
 

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