Abstract In ‘Do Virtual Particles Exist’, I argued that virtual particles do not, in fact, exist. I review that argument in section I of this paper. Then in section II I present the argument from a different point of view, emphasizing the role of the propagator, and in section III I look at the connection between the Fayddeev-Popov ghost fields and the problem of virtual particles.
Abstract In ‘Do Virtual Particles Exist’, I argued that virtual particles do not, in fact, exist. I review that argument in section I of this paper. Then in section II I present the argument from a different point of view, emphasizing the role of the propagator, and in section III I look at the connection between the Fayddeev-Popov ghost fields and the problem of virtual particles.
The question of whether virtual quantum particles exist is considered here in light of previous critical analysis and under the assumption that there are particles in the world as described by quantum field theory. The relationship of the classification of particles to quantum-field-theoretic calculations and the diagrammatic aids that are often used in them is clarified. It is pointed out that the distinction between virtual particles and others and, therefore, judgments regarding their reality have been made on basis of these methods rather than on their physical characteristics. As such, it has obscured the question of their existence. It is here argued that the most influential arguments against the existence of virtual particles but not other particles fail because they either are arguments against the existence of particles in general rather than virtual particles per se, or are dependent on the imposition of classical intuitions on quantum systems, or are simply beside the point. Several reasons are then provided for considering virtual particles real, such as their descriptive, explanatory, and predictive value, and a clearer characterization of virtuality—one in terms of intermediate states—that also applies beyond perturbation theory is provided. It is also pointed out that in the role of force mediators, they serve to preclude action-at-a-distance between interacting particles. For these reasons, it is concluded that virtual particles are as real as other quantum particles.
Abstract The aim of this volume of essays is to delineate and examine a range of topics which represent a systematic account of the nature and implications of QFT. The contributors, who include Michael Redhead, James T. Cushing, Paul Teller, and Gordon Fleming, approach QFT from a variety of standpoints. Part I offers two different interpretations of the value of studying the foundations of QFT as an area of separate metaphysical research. Parts II and III consider the metaphysical and methodological implications of such issues as the problem of the status of virtual particles; the technique of renormalization; and the role of covariance principles. Part IV examines the mathematical foundations of QFT.
Despite its name, Quantum Field Theory (QFT) has been built to describe interactions between localizable particles. For this reason the actual formalism of QFT is partly based on a suitable generalization of the one already used for systems of point particles. This circumstance gives rise to a number of conceptual problems, stemming essentially from the fact that the existence within QFT of non-equivalent representations implies the existence of field theories allowing, within the same theory, different, inequivalent, descriptions of particles. This led some authors to claim that in QFT the concept itself of particle should be abandoned. In this paper we will shortly discuss the validity of this claim, as well as the possibilities, so far existing, of building alternative versions of QFT, not designed in advance to allow some kind of particle representation. We will also spend some words about the generalizations of the concept itself of particle which could grant for a better cohabitation of particles and fields within a wider formulation of QFT. The latter is indispensable if we want to extend the range of application of QFT from particle physics or simple condensed matter physics to other domains of scientific research.
Abstract Much attention has been directed to the philosophical implications of quantum field theory (QFT) in recent years; this paper attempts a survey in low-technical terms. First the relations of QFT to other kinds of theory, classical and quantum, particle and field, are discussed. Then various formulations of QFT are introduced, along with related interpretations. Finally a review is made of some of the most interesting foundational problems. For our discussion of the foundations of quantum field theory (QFT) it will be useful to have a map showing where QFT stands in relation to other physical theories. Figure 1 locates theories as points of a three-dimensional lattice: describing particles or fields, formulated in different spacetimes and either classical or quantum. Consider the classical plane of Figure
This is an opinionated survey of some interpretive puzzles in quantum field theory. The problem of inequivalent representations is sketched, including its connections with competing accounts of physical equivalence. The controversy between variant formulations of the theory, algebraic versus Lagrangian, is given a conciliatory resolution. Arguments against particles are addressed, demarcating clearly between different forms of particle interpretation. Field interpretations are then considered, including wavefunctional, spacetime state realist and Heisenberg operator realist interpretations. Ruetsche’s coalesced structure interpretation is presented and juxtaposed with an alternative, more traditional view of the theory’s laws and state space. Finally, the CPT theorem is discussed, together with its implications about the nature of spacetime.
There is an uncomfortable question that particle physics has spent half a century answering with polite silence: virtual particles contribute to some of the most precise calculations science knows —the Lamb shift, the anomalous gyromagnetic factor of the electron, the Casimir effect —and yet none has ever been seen. They leave no trace in a detection chamber. They have no past and no future outside the vertex where they are born and vanish in the same instant. They contribute to the real without themselves being real objects. This work asks quantum field theory (QFT) to change not a single number: it asks QFT to say precisely what it is actually calculating.The proposal, from the Foundation of Fundamental Correlations (FCF) [1, 2], is an ontological reordering, not a mathematical one. Quantum fields are reinterpreted as the Type 3 expression of Type 1 correlations deployed over the geometric region where they express themselves; the harmonic oscillators upon which QFT builds its formalism are the form that expression takes when the opportunities for point momentum are full, not the ontology of the objects it describes. And virtual particles, the heart of the problem, are identified as Type 2 correlations that restrict without transiting to Type 3 —present, active, but never expressed as something that can be seen.This dissolves the paradox without forcing anything: the virtual ones add up because they restrict, and they are not observed individually because they are not entities that can be observed —they are restrictions, and a restriction does not see itself; it is seen in what it shapes. QFT, it is argued here, calculates well and names badly: its mathematics captures exactly the geometry of the restriction, even as it calls it a population of ghost particles. It is shown that the complete accounting —Lamb, Casimir, g − 2 —preserves every number under this reading, because what changes is the ontology, not the calculation. And the coincidence between QFT and FCF at the ~10¹²⁰ of the vacuum [3] ceases to be a stumble of the theory and becomes its correct prediction, once one distinguishes what is expressed from what merely restricts.