One of the problems of the many worlds interpretation (MWI) of quantum mechanics is about the ontological status of multiple worlds. In the MWI, the multiple worlds are quasi-classical, and the quasi-classical worlds are considered as emergence and pattern. However, the ontological understanding about the quasi-classical realms remains ambiguous. This article aims to clarify the ontological status of the quasi-classicality in the MWI. In particular, the notion of emergence and pattern has been investigated in the philosophy of science. The investigation about these notions provides a refined ontology of many worlds interpretation.
One of the problems of the many worlds interpretation (MWI) of quantum mechanics is about the ontological status of multiple worlds. In the MWI, the multiple worlds are quasi-classical, and the quasi-classical worlds are considered as emergence and pattern. However, the ontological understanding about the quasi-classical realms remains ambiguous. This article aims to clarify the ontological status of the quasi-classicality in the MWI. In particular, the notion of emergence and pattern has been investigated in the philosophy of science. The investigation about these notions provides a refined ontology of many worlds interpretation.
David Wallace's ``The Emergent Multiverse" is the most recent complete presentation of\na version of Everett's theory of quantum mechanics that has attracted much scientific\nactivity in the past decade. I present a brief sketch of Wallace's solution to the measurement\nproblem, arguing that the many-worlds interpretation is not as far-fetched as it is\noften conceived to be. Taking the wavefunction as the fundamental ontology, it claims\nto solve the measurement problem by recognizing certain (quasi-classical) patterns of\nthe wavefunction in 3N-dimensional configuration space that functionally behave like\nthe (classical) configuration-space pattern of a N-particle system described by classical\nmechanics. In this sense, structures within the universal wavefunction are identified\nwith classical `worlds' at the coarse-grained level. I highlight two elements of this work:\nthe role of emergence and the functionalist framework that Wallace imports through\nwhat he calls `Dennett's criterion'. This criterion appeals to the virtue of usefulness\n(in the form of predictability and explanatory power) as a criterion for the reality of\n`patterns'. \n\nIt is shown that, due to decoherence, quasi-classical worlds emerge weakly, similar\nto that of the emergence of thermodynamic temperature from statistical physics, in the\nsense that they are autonomous and unexpected with respect to the lower-level domain\n(as opposed to strong emergence of some insuper et supra high-level ontology). However,\nthe use of Dennett's criterion obscures this result, laying bare some philosophical issues,\nwhich we address over three axes of distinctions: (i) the objective/subjective-axis, (ii)\nthe quantitative/qualitative-axis within the framework of intertheoretic reduction and\n(iii) the ontological/epistemological-axis.\n\nFirst, Daniel Dennett's `real patterns' are compared to Wallace approach to patterns.\nThen, I point out (i) an analogy with Bas van Fraassen's idea of causal patterns\nthat become salient due to pragmatic explanation, namely that in the context of a pragmatic\ngoal the quasi-classical pattern is made salient over other objectively existing,\nnon-classical, patterns. I conclude that in the absence of human goals there is no reason\nto regard the quasi-classical pattern as `more real' than other patterns. In analogy to\nDennett's `intentional stance', Wallace is committed to a `classical stance', equivalent\nto breaking Hilbert space democracy of bases. \n\nAlthough Wallace's version is a weaker one, his (ii) relations between theories\nbare resemblance to the reductionist program, and I argue that, next to quantitative\ndeduction, additional conceptual `bridge principles' à la Ernest Nagel are needed.\nThe appeal to usefulness as a criterion for reality (iii), I claim, is not necessary\nto solve the measurement problem itself, but has the further (unwarranted) goal of\nestablishing `real' worlds. I spell out a solution to the measurement problem, the\nmany-minds theory, which solves the problem along the same lines as The Emergent\nMultiverse, with the exception that the - although the quantum world itself is real\n- the classical worlds with definite properties are beliefs in the superposed brains of\nobservers.
Since the 1970s, the Everett-Wheeler many-worlds interpretation (MWI) of Quantum Mechanics (1955) has been much in the news. One wonders about the worlds in question, their branches, their splittings, their number. It is most often ignored that this language is not that of Everett, whom Wheeler very quickly stopped supporting. Moreover, for some interpreters, the real meaning of Everett ideas is not the coexistence of many worlds, but the existence of a single quantum one. In this context, what should we think of attempts to verify Everett thesis? What about the connexion between MWI and the cosmological multiverse? How to understand the links between the quantum world and the classical one? This article tries to answer some of these questions.
The philosophy of science in general, and the philosophy of physics in particular, have increasingly focused on cases of reduction and emergence in recent decades. While the paradigmatic examples arise in the context of thermodynamics and classical statistical mechanics, relevant cases have also emerged in the philosophy of quantum mechanics, such as that of quasiparticles. Traditionally, these entities have been regarded as mere mathematical tools that do not contribute to the construction of quantum ontology. However, this position has recently been challenged, and frameworks have been proposed in which some of these objects acquire a significant ontological status. In particular, phonons have been considered a case of emergence that may have either an epistemic or an ontological character. In this paper, we further enrich the discussion by emphasizing that quantum mechanics only refers to entities in the real world through the adoption of a specific interpretation. A century after the development of quantum theory, there is still no consensus on how to interpret it, and multiple competing interpretations are currently proposed. Consequently, the outcome may vary depending on the interpretation adopted. Based on this, we will show that the choice of interpretation not only influences the conceptual understanding of quantum mechanics but also determines the identification of its fundamental entities. Specifically, we will argue that, under the Modal-Hamiltonian Interpretation, phonons acquire a fundamental status, challenging the standard reading of their emergence and their relationship to quantum ontology.
The Many-worlds Interpretation (MWI) of quantum mechanics has captivated physicists and philosophers alike since its inception in the mid-20th century. This paper explores the historical roots, evolution, and implications of the MWI within the context of quantum theory. Beginning with an overview of early developments in quantum mechanics and the emergence of foundational interpretations, we delve into the origins of the MWI through the groundbreaking work of physicist Hugh Everett III. Everett's doctoral thesis proposed a radical solution to the measurement problem, positing the existence of multiple branching universes to account for quantum phenomenon. We trace the evolution of the MWI, examining its refinement and elaboration by subsequent physicists such as John Wheeler. Furthermore, we discuss the MWI's impact on contemporary physics, including its connections to quantum information theory and ongoing experimental tests. By providing a comprehensive analysis of the MWI's historical development and current relevance, this paper offers insights into one of the most provocative interpretations of quantum mechanics and its implications for our understanding of the universe.
The articles provides a phenomenological reading of the Many-Worlds Interpretation (MWI) of quantum mechanics and its answer to the measurement problem, or the question of “why only one of a wave function’s probable values is observed when the system is measured.” Transcendental-phenomenological and hermeneutic-phenomenological approaches are employed. The project comprises four parts. Parts one and two review MWI and the standard (Copenhagen) interpretation of quantum mechanics. Part three reviews the phenomenologies. Part four deconstructs the hermeneutics of MWI. It agrees with the confidence the theory derives from its (1) unforgiving appropriation of the Schrödinger equation and (2) association of branching universes with the evolution of the wave function insofar as that understanding comes from the formalism itself. Part four also reveals the hermeneutical shortcomings of the standard interpretation.