Identical Particles in Quantum Mechanics: Against the Received View (original) (raw)
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Identical particles in quantum mechanics: favouring the Received View
The so-called Received View (RV) on quantum non-individuality states, basically, that quantum particles are not individuals. It has received an amount of criticism in the recent literature, most of it concerning the relation between the RV and the relation of identity. In this chapter we carefully characterise a family of concepts involved in clarifying the view, indicating how the very idea of failure of identity, commonly used to define the RV, may be understood. By doing so, we hope to dissipate some misunderstandings about the RV, which shall also be seen as evidence of its tenability.
Identical Quantum Particles as Distinguishable Objects
Journal for General Philosophy of Science, 2020
According to classical physics particles are basic building blocks of the world. These classical particles are distinguishable objects, individuated by unique combinations of physical properties. By contrast, in quantum mechanics the received view is that particles of the same kind (“identical particles”) are physically indistinguishable from each other and lack identity. This doctrine rests on the quantum mechanical (anti)symmetrization postulates together with the “factorist” assumption that each single particle is represented in exactly one factor space of the tensor product Hilbert space of a many-particle system. Even though standard in theoretical physics and the philosophy of physics, the assumption of factorism and the ensuing indistinguishability of particles are problematic. Particle indistinguishability is irreconcilable with the everyday meaning of “particle”, and also with how this term is used in the practice of physics. Moreover, it is a consequence of the standard vi...
Identical Quantum Particles, Entanglement and Individuality
2019
Particles in classical physics are distinguishable objects, which can be picked out individually on the basis of their unique physical properties. By contrast, in quantum mechanics the standard view is that particles of the same kind (``identical particles'') are completely indistinguishable from each other. This standard view is problematic: Particle indistinguishability is irreconcilable not only with the very meaning of ``particle'' in ordinary language and in classical physical theory, but also with how this term is used in the practice of present-day physics. Moreover, the indistinguishability doctrine prevents a smooth transition from quantum particles to what we normally understand by ``particles'' in the classical limit of quantum mechanics. Elaborating on earlier work, we here discuss an alternative to the standard view that avoids these and similar problems. As it turns out, this alternative approach connects to recent discussions in quantum informa...
The Logic of Identity: Distinguishability and Indistinguishability in Classical and Quantum Physics
The notion that particles can be indistinguishable in a fundamental sense, which poses a challenge to traditional notions of individuality and identity, has first come up in the context of classical statistical mechanics. In particular, the Gibbs paradox has been interpreted as a sign of the untenability of the classical concept of a particle and as a premonition that quantum theory is needed to make sense of the situation. These ideas have been criticized in the literature, and completely classical solutions of the Gibbs paradox have been proposed. We shall argue, however, that although the criticism was justified, the proposed solutions have not gone to the heart of the matter. As we shall show, the solution of the Gibbs paradox in classical physics is in fact unrelated to fundamental distinguishability issues; only distinguishability in a pragmatic sense plays a role (in this we develop ideas of van Kampen [10]). With regard to quantum mechanics we shall show that the paradox survives in basically the same form even here, in spite of the quantum mechanical (anti-)symmetrization postulates.
Synthese, 1986
Two difierent concepts of distinguishability are often mixed up in attempts to derive in quantum mechanics the (anti)symmetry of the wave function from indistinguishability of identical particles. some of these attempts are analyzed and shown to be defective. It is argued that, although identical particles should be considered as observationally indistinguishable in (anti)symmetric states, they may be considered to be conceptually distinguishable. These two notions of (in)distinguishabitity have quite different physical origins, the former one being related to observations while the latter has to do with the preparation of the system. wILLEM M. DE MUYNCK AND GIDI P. VAN LIEMPD
Identity in Physics: Properties, Statistics and the (Non-)Individuality of Quantum Particles
EPSA Philosophy of Science: Amsterdam 2009, 2011
This paper discusses the issue of the identity and individuality (or lack thereof) of quantum mechanical particles. It first reconstructs, on the basis of the extant literature, a general argument in favour of the conclusion that such particles are not individual objects. Then, it critically assesses each one of the argument's premises. The upshot is that, in fact, there is no compelling reason for believing that quantum particles are not individual objects.
How to Distinguish Identical Particles. the General Case
Eprint Arxiv Quant Ph 0611049, 2006
The many-identical-particle quantum correlations are revisited utilizing the machinery of basic group theory, especially that of the group of permutations. It is done with the purpose to obtain precise definitions of effective distinct particles, and of the limitations involved. Namely, certain restrictions allow one to distinguish identical particles in the general case of N of them, and of J clusters of effectively distinct particles, where N and J are arbitrary integers (but 1<J<(N+1)). Mutually orthogonal, single-particle distinguishing projectors (events or ptoperties), J of them, are the backbone of the construction. The general results are exemplified by local quantum mechanics, and by the case of nucleons. The former example suits laboratory experiments, and a critical view of it is presented.
Identity and Indiscernibility in Quantum Mechanics
Palgrave - Macmillan, 2021
This book analyzes metaphysical consequences of the quantum theory of many particles with respect to the fundamental notions of identity, individuality and discernibility. The main focus is on the proper interpretation of the quantum formalism in relation to the role of permutation invariance and the adequate representation of the properties of individual subsystems. Two main approaches to the issue of the individuation of quantum particles are distinguished and thoroughly discussed. These approaches differ radically with respect to their metaphysical consequences – while one of them implies the complete indiscernibility of quantum particles of the same kind, the other one restores the possibility of discerning individual particles by their properties. We connect the problem of quantum individuation and discernibility with an analysis of the concept of quantum entanglement, and we also discuss identity over time and in counterfactual scenarios.
Journal of Physics A: Mathematical and General, 2005
We consider the possibility that all particles in the world are fundamentally identical, i.e., belong to the same species. Different masses, charges, spins, flavors, or colors then merely correspond to different quantum states of the same particle, just as spin-up and spin-down do. The implications of this viewpoint can be best appreciated within Bohmian mechanics, a precise formulation of quantum mechanics with particle trajectories. The implementation of this viewpoint in such a theory leads to trajectories different from those of the usual formulation, and thus to a version of Bohmian mechanics that is inequivalent to, though arguably empirically indistinguishable from, the usual one. The mathematical core of this viewpoint is however rather independent of the detailed dynamical scheme Bohmian mechanics provides, and it amounts to the assertion that the configuration space for N particles, even N "distinguishable particles," is the set of all N -point subsets of physical 3-space.