Bonn 2025 – wissenschaftliches Programm
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AGPhil: Arbeitsgruppe Philosophie der Physik
AGPhil 2: Foundations of Physics II
AGPhil 2.1: Vortrag
Montag, 10. März 2025, 17:00–17:30, HS XVII
Are four levels of multiverses enough? — •Phillip Helbig1 and Maura Cassidy Burke2 — 1Maintal, Germany — 2Freudenthal Institute, Utrecht University, Netherlands
Tegmark classified multiverses into four levels: I: regions in our Universe but outside our particle horizon and hence not (yet) observable by us; II: independent Level I universes in the context of eternal inflation and/or with different laws of physics; III: many universes corresponding to the many worlds in the many-worlds interpretation of quantum mechanics; IV: Tegmark's mathematical multiverse in which every mathematical object actually exists. We suggest that Tegmark's Level II multiverse actually refers to two distinct concepts and propose a change in the terminology in order to take that into account.
Levels II and III are the types of multiverse usually discussed, and the definitions of the levels other than II are clear. Level II is most often thought of as consisting of various universes within the concepts of eternal inflation, the string-theory landscape, or brane-world cosmology, but at the same time as universes with different values of physical constants or even different laws of physics. On the other hand, such theories clearly depend on some fundamental laws of physics which must be common to all universes in such a multiverse, thus a distinction is needed. We thus see a need for a level higher than what is usually thought of as the Level II multiverse, which of all of the levels also most closely corresponds to historical multiverse concepts.
Keywords: cosmology; multiverse; laws of physics; cosmology: history