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Question69
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Does unitarity have to be obeyed in a full quantum gravity model?
As @A. Neumaier says, it depends on the model. And nobody currently has one that works. But in any case, we can't discuss "quantum gravity" in the abstract. Discussion needs to be about some particular model that has been published in a peer-reviewed paper. And, as @A. Neumaier correctly points out, such discussions belong in the Beyond the Standard Model forum.Question69 said:Does unitarity have to be obeyed in a full quantum gravity model?
Unitarity is a fundamental principle in physics that states that the total probability of all possible outcomes of a quantum system must equal 1. In the context of GR and QFT, unitarity requires that the probability of all possible outcomes of a quantum gravitational system must also equal 1.
Unitarity is a key requirement for any successful theory of quantum gravity. This is because a full QG model must be able to reconcile the principles of GR and QFT, which are currently incompatible. Unitarity ensures that any new theory of quantum gravity is consistent with the principles of both theories.
If unitarity is violated in a QG model, it would mean that the theory is not consistent with the principles of GR and QFT. This could lead to inconsistencies and contradictions in the predictions of the theory, making it less reliable and less useful for understanding the nature of the universe.
One way to test for unitarity in GR+QFT models is through experiments and observations. Scientists can look for any violations of the principle of unitarity in data collected from particle accelerators or astrophysical observations. They can also use mathematical models and simulations to test the consistency of a proposed QG model with the principles of unitarity.
There are currently many proposed full QG models, but none have been fully confirmed or accepted by the scientific community. However, some models, such as string theory and loop quantum gravity, have shown promising results in terms of obeying unitarity. Further research and experimentation are needed to fully understand and confirm the validity of these models.