CPT Violation and Energy Conservation: Explained!

In summary, natural processes are invariant under CPT, but CP violation has been observed experimentally. This means that there are processes that are violated under time reversal. However, the Noether theorem, which applies to continuous symmetries, like time-translation symmetry, implies that energy is conserved. So, breaking time-reversal symmetry also means breaking time-translation symmetry, leading to a breakdown of energy conservation. However, in general relativity and cosmological scenarios, energy conservation is not well-defined.
  • #1
Silviu
624
11
Hello! I read that natural processes are invariant under CPT (based on some theorem) and that CP violation was observed experimentally. So this would mean that there are processes that are violated under time reversal. However, based on Noether theorem, this would mean that the energy is not conserved in these kind of processes, but I read many times that it has been no process in which the conservation of energy to be violated. Can someone explain this to me and tell me where is the flaw in my logic? Thank you!
 
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  • #2
Time reversal is a discrete transformation while noether' s theorem is about continuous transformations. How would you derive the breakdown of energy conservation from T-variance?
 
  • #3
See: https://www.physicsforums.com/threads/noether-theorem-cp-violation-energy-is-not-conserved.303056/. Basically, T is the discrete time-inversion symmetry ##t \rightarrow -t##, whereas Noether's theorem applies only to continuous symmetries, like the time-translation symmetry ##t \rightarrow t + \epsilon## that gives energy conservation. Breaking T (i.e. breaking the isotropy of time) does imply breaking time-translation (i.e. the homogeneity of time), and it is the latter that gives energy conservation, not the former.

Of course, in general relativity energy conservation is more complicated and not necessarily well-defined, and in cosmological scenarios with the expansion of the universe time-translational symmetry, and thus energy conservation, are also violated. See:
https://physics.stackexchange.com/questions/74266/conservation-of-energy-and-cp-violation,
https://en.wikipedia.org/wiki/Conservation_of_energy#Relativity, and
https://en.wikipedia.org/wiki/ADM_formalism#ADM_energy_and_mass.
 
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1. What is CPT violation?

CPT violation is a theoretical concept in physics that suggests the laws of charge conjugation (C), parity (P), and time reversal (T) may not hold true in all physical processes. This means that there may be instances where the charge, parity, or direction of time in a physical system may not behave as expected.

2. How does CPT violation affect energy conservation?

CPT violation does not directly affect energy conservation. However, the existence of CPT violation implies that there may be processes that do not conserve energy, as energy conservation is a consequence of the laws of CPT symmetry. This means that CPT violation may lead to new possibilities for energy to be created or destroyed in certain physical processes.

3. Is CPT violation experimentally proven?

There has been no conclusive experimental evidence for CPT violation so far. However, there have been some theoretical models that predict CPT violation, and experiments are ongoing to test these predictions. So far, all experimental results have been consistent with the laws of CPT symmetry.

4. Why is CPT violation important in physics?

CPT violation is important because it challenges our current understanding of the fundamental laws of physics. If CPT violation is confirmed, it would require a major rethinking of our current theories and could lead to the development of new, more comprehensive models. Additionally, CPT violation could potentially provide explanations for some unsolved mysteries in physics, such as the imbalance of matter and antimatter in the universe.

5. How does CPT violation relate to the search for a theory of everything?

CPT violation is a topic of interest in the search for a theory of everything because it may provide clues to resolving some of the discrepancies and limitations of current theories, such as the inability to reconcile gravity with the other fundamental forces. If CPT violation is confirmed, it could lead to the development of a more unified and comprehensive theory that can explain all physical phenomena in the universe.

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