# Berlin 2014 – wissenschaftliches Programm

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# AGPhil: Arbeitsgruppe Philosophie der Physik

## AGPhil 7: Quantum-Classical Divide V

### AGPhil 7.3: Vortrag

### Freitag, 21. März 2014, 15:15–15:45, SPA SR22

**Decoherence and the Many Worlds Interpretation** — •Carsten Thomas Weigelt — University, Bonn, Germany

The theory of decoherence gives us a good account (at least for open systems) of how classical properties emerge from the quantum world. Recent experiments based on decoherence offers strong arguments against the quantum-classical division proposed by the early Copenhagen Interpretation.

But even if decoherence may support the view that quantum mechanics can be considered as fundamental theory the question remains if this sheds new light to the question of how a realistic interpretation of quantum theory can be achieved? In the last years proponents of decoherence pointed out that the theory fits perfectly into the framework of many worlds interpretations (Zurek 2003, Wallace 2012).

The question that I will address is, in what sense these interpretations can be considered as realistic interpretations? To answer this question I will argue that in the context of decoherence we have strong reasons to interpret quantum states in a realistic sense. A problem for many worlds interpretations arises when the meaning of Everett's relative states is considered since these interpretations strongly dependent on the interpretation of relative states. I will show that einselection proposed by the decoherence theory will determine Everett's relative states in an objective sense but these states must be interpreted as epistemic states. I will conclude that this ambiguity between realistic interpreted quantum states and epistemic relative states limits the strict realistic character of many worlds interpretation.