Interpretation of Quantum Mechanics and the Ontology of Phonons

Abstract

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.