Conjecture that the crossed-product algebra is no longer type III
Conjecture that the crossed-product algebra is no longer type III
Let be a local von Neumann factor, let be its modular action, and let be the algebra generated by together with the modular evolution . For a typical observable of , let its spectral projectors be formed through the coupling of elements of and . Crossed-product type conjecture. Such spectral projectors are not related by partial isometries to projectors in, for example, or to the identity projector , because their information contents differ. Hence is no longer of type . The paper explicitly says that this is not proved mathematically and argues for it on physical grounds. It is intended to explain how coupling a local algebra to Tomita evolution can change the type of the resulting algebra.
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Primary source
Manfred Requardt, “The Crossed Product, Modular (Tomita) Dynamics and its Role in the Transition of Type III to Type II_ v.Neumann Algebras and Connections to Quantum Gravity”, arXiv:2507.01419 (2025).
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