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A virtual particle is an elementary particle in a quantum field theory that serves to symbolise the interaction of its counterparts, the so called real particles. In the last 20 years, philosophers of physics have put forth several arguments for and against an interpretation of virtual particles as being like ordinary objects in space and time. In this article, I will attempt to systematise the major arguments and argue that no proargument is ultimately satisfactory, and that only one contraargument—that of (...) 

An epistemological interpretation of quantum mechanics hinges on the claim that the distinctive features of quantum mechanics can be derived from some distinctive features of an observational basis. Old and new variations of this theme are listed. The program has a limited success in nonrelativistic quantum mechanics. The crucial issue is how far it can be extended to quantum field theory without introducing significant ontological postulates. A C*formulation covers algebraic quantum field theory, but not the standard model. Julian Schwinger’s anabatic (...) 

Everything you always wanted to know about structural realism but were afraid to ask Content Type Journal Article Pages 227276 DOI 10.1007/s1319401100257 Authors Roman Frigg, Department of Philosophy, Logic and Scientific Method, London School of Economics and Political Science, Houghton Street, London, WC2A 2AE UK Ioannis Votsis, Philosophisches Institut, HeinrichHeineUniversität Düsseldorf, Universitätsstraße 1, Geb. 23.21/04.86, 40225 Düsseldorf, Germany Journal European Journal for Philosophy of Science Online ISSN 18794920 Print ISSN 18794912 Journal Volume Volume 1 Journal Issue Volume 1, Number 2. 

I analyse the conceptual and mathematical foundations of Lagrangian quantum field theory (QFT) (that is, the ‘naive’ (QFT) used in mainstream physics, as opposed to algebraic quantum field theory). The objective is to see whether Lagrangian (QFT) has a sufficiently firm conceptual and mathematical basis to be a legitimate object of foundational study, or whether it is too illdefined. The analysis covers renormalisation and infinities, inequivalent representations, and the concept of localised states; the conclusion is that Lagrangian QFT (at least (...) 

String theory promises to be able to provide us with a working theory of quantum gravity and a unified description of all fundamental forces. In string theory there are so called ‘dualities’; i.e. different theoretical formulations that are physically equivalent. In this article these dualities are investigated from a philosophical point of view. Semantic and epistemic questions relating to the problem of underdetermination of theories by data and the debate on realism concerning scientific theories are discussed. Depending on ones views (...) 

Symposium review of Richard Healey, Gauging What’s Real: The Conceptual Foundations of Contemporary Gauge Theories. Oxford: Oxford University Press, 2007. Pp. 297. $99.00 HB. 

The logic of gauge theory is considered by tracing its development from general relativity to YangMills theory, through Weyl's two gauge theories. A handful of elementswhich for want of better terms can be called \emph{geometrical justice}, \emph{matter wave}, \emph{second clock effect}, \emph{twice too many energy levels}are enough to produce Weyl's second theory; and from there, all that's needed to reach the YangMills formalism is a \emph{nonAbelian structure group} (say $\mathbb{SU}\textrm{(}N\textrm{)}$). 

In 1894 Pierre Curie announced what has come to be known as Curie's Principle: the asymmetry of effects must be found in their causes. In the same publication Curie discussed a key feature of what later came to be known as spontaneous symmetry breaking: the phenomena generally do not exhibit the symmetries of the laws that govern them. Philosophers have long been interested in the meaning and status of Curie's Principle. Only comparatively recently have they begun to delve into the (...) 

Effective field theories have been a very popular tool in quantum physics for almost two decades. And there are good reasons for this. I will argue that effective field theories share many of the advantages of both fundamental theories and phenomenological models, while avoiding their respective shortcomings. They are, for example, flexible enough to cover a wide range of phenomena, and concrete enough to provide a detailed story of the specific mechanisms at work at a given energy scale. So will (...) 

I describe how relativistic field theory generalizes the paradigm property of material systems, the possession of mass, to the requirement that they have a mass–energy–momentum density tensor T µ associated with them. I argue that T µ does not represent an intrinsic property of matter. For it will become evident that the definition of T µ depends on the metric field g µ in a variety of ways. Accordingly, since g µ represents the geometry of spacetime itself, the properties of (...) 



Debates about the ontological implications of the general theory of relativity have long oscillated between spacetime substantivalism and relationism. I evaluate such debates by claiming that we need a third option, which I refer to as “structural spacetime realism.” Such a tertium quid sides with the relationists in defending the relational nature of the spacetime structure, but joins the substantivalists in arguing that spacetime exists, at least in part, independently of particular physical objects and events, the degree of “independence” being (...) 

I examine the relation between explanation and unification in both the original Kaluza–Klein theory, which originated in the works of Theodor Kaluza and Oskar Klein in the 1920s, and in the modern Kaluza–Klein theories which date back to the late 1970s and which are still considered by the majority of the physics community to be the best hope for a complete unified theory of all fundamental interactions. I use the conclusions of this case study to assess the merits of Philip (...) 

The claim of this paper is that we should envisage physicalism as an ontological holism. Our current basic physics, quantum theory, suggests that, ontologically speaking, we have to assume one global quantum state of the world; many of the properties that are often taken to be intrinsic properties of physical systems are in fact relations, which are determined by that global quantum state. The paper elaborates on this conception of physicalism as an ontological holism and considers issues such as supervenience, (...) 



In previous work, I described several examples combining reduction and emergence: where reduction is understood a la Ernest Nagel, and emergence is understood as behaviour that is novel. Here, my aim is again to reconcile reduction and emergence, for a case which is apparently more problematic than those I treated before: renormalization. My main point is that renormalizability being a generic feature at accessible energies gives us a conceptually unified family of Nagelian reductions. That is worth saying since philosophers tend (...) 

The objective of this thesis is to present a naturalised metaphysics of information, or to naturalise information, by way of deploying a scientiﬁc metaphysics according to which contingency is privileged and apriori conceptual analysis is excluded (or at least greatly diminished) in favour of contingent and defeasible metaphysics. The ontology of information is established according to the premises and mandate of the scientiﬁc metaphysics by inference to the best explanation, and in accordance with the idea that the primacy of physics (...) 

In recent years, a ''change in attitude'' in particle physics has led to our understanding current quantum field theories as effective field theories (EFTs). The present paper is concerned with the significance of this EFT approach, especially from the viewpoint of the debate on reductionism in science. In particular, I shall show how EFTs provide a new and interesting case study in current philosophical discussion on reduction, emergence, and interlevel relationships in general. 



The theoretical physicist Paul Dirac rejected, explicitly on aesthetic grounds, a successful theory known as quantum electrodynamics (QED), which is the prototype for the family of theories known as quantum field theories (QFTs). Remarkably, the theoretical physicist Steven Weinberg, also largely on aesthetic grounds, supports QED and other QFTs. In order to evaluate these opposing aesthetic views a short introduction to the physical properties of QFTs is presented together with a detailed analysis of the aesthetic claims of Dirac and Weinberg. (...) 

In this paper I focus on the impact on structuralism of the quantum treatment of objects in terms of symmetry groups and, in particular, on the question as to how we might eliminate, or better, reconceptualise such objects in structural terms. With regard to the former, both Cassirer and Eddington not only explicitly and famously tied their structuralism to the development of group theory but also drew on the quantum treatment in order to further their structuralist aims and here I (...) 

Zeno’s Arrow and Nāgārjuna’s Fundamental Wisdom of the Middle Way Chapter 2 contain paradoxical, dialectic arguments thought to indicate that there is no valid explanation of motion, hence there is no physical or generic motion. There are, however, diverse interpretations of the latter text, and I argue they apply to Zeno’s Arrow as well. I also find that many of the interpretations are dependent on a mathematical analysis of material motion through space and time. However, with modern philosophy and physics (...) 

In the theorydominated view of scientific experimentation, all relations of theory and experiment are taken on a par; namely, that experiments are performed solely to ascertain the conclusions of scientific theories. As a result, different aspects of experimentation and of the relation of theory to experiment remain undifferentiated. This in turn fosters a notion of theoryladenness of experimentation that is too coarsegrained to accurately describe the relations of theory and experiment in scientific practice. By contrast, in this article, I suggest (...) 

This is a preliminary version of an article to appear in the forthcoming Ashgate Companion to the New Philosophy of Physics.In it, I aim to review, in a way accessible to foundationally interested physicists as well as physicsinformed philosophers, just where we have got to in the quest for a solution to the measurement problem. I don't advocate any particular approach to the measurement problem (not here, at any rate!) but I do focus on the importance of decoherence theory to (...) 

Quantum field theory (QFT) presents a genuine example of the underdetermination of theory by empirical evidence. There are variants of QFT—for example, the standard textbook formulation and the rigorous axiomatic formulation—that are empirically indistinguishable yet support different interpretations. This case is of particular interest to philosophers of physics because, before the philosophical work of interpreting QFT can proceed, the question of which variant should be subject to interpretation must be settled. New arguments are offered for basing the interpretation of QFT (...) 

This paper places Julian Schwinger's development of the Euclidean Green's function formalism for quantum field theory in historical context. It traces the techniques employed in the formalism back to Schwinger's work on waveguides during World War II, and his subsequent formulation of the Minkowski space Green's function formalism for quantum field theory in 1951. Particular attention is dedicated to understanding Schwinger's physical motivation for pursuing the Euclidean extension of this formalism in 1958. 

In a recent book (The Metaphysics within Physics), Tim Maudlin reconstructs metaphysics by taking inspiration from the gauge theories interpreted in the ber bundle framework. I call his project the "fiber bundle metaphysics". Primarily targeted not to Humean Supervenience, but to any metaphysics employing the relation of resemblance among objects (D. Lewis, D. Armstrong), Maudlin's project is novel and promising. I critically analyze the arguments by identifying several objections stemming rst from metaphysics. The metaphysician questions whether gauge theory represented through (...) 

In this article the Dirac equation is used a guideline to see the historical emergence of the concept of quanta, associated with the quantum field. In P. Jordan’s approach, the electron as quanta results from the quantization of a classical field described by the Dirac equation. The concept of quanta becomes a central piece in the applications of the theory and is seen as fundamental in the intelegibility of the interaction between fields, being the Fock space the natural mathematical structure (...) 

Cao makes two claims of particular philosophical interest, in his book "The Conceptual Development of 20th Century Field Theories". (i) The history of these developments refutes Kuhn's relativistic epistemology, and (tacitly) (2) the question of realism in quantum field theory can be addressed independent of one's views on the probem of measurement. I argue that Cao is right on the first score, although for reasons different from the ones he cites, but wrong on the second. In support of the first (...) 

PhD dissertation addressing what can be called conceptualmathematical anomalies in quantum electrodynamics. This work can be seen as following the line of philosophy of physics studies of quantum field theory that started to emerge in a systematic way in the early eighties of last century. One example is Teller’s work on standard quantum electrodynamics.In this work, by following a historical approach, I will return to the standard version of quantum electrodynamics, which is the only one available when we want to (...) 

This essay demonstrates the inadequacy of contemporary substantivalist and relationist interpretations of quantum gravity hypotheses via an historical investigation of the debate on the underlying ontology of space in the seventeenth century. Viewed in the proper context, there are crucial similarities between seventeenth century theories of space and contemporary work on the ontological foundations of spacetime theories, and these similarities challenge the utility of the substantival/relational dichotomy by revealing a host of underlying conceptual issues that do not naturally align with (...) 



Philosophical interpretations of theories generally presuppose that a theory can be presented as a consistent mathematical formulation that is interpreted through models. Algebraic quantum field theory (AQFT) can fit this interpretative model. However, standard Lagrangian quantum field theory (LQFT), as well as quantum electrodynamics and nuclear physics, resists recasting along such formal lines. The difference has a distinct bearing on ontological issues. AQFT does not treat particle interactions or the standard model. This paper develops a framework and methodology for interpreting (...) 

After decades of neglect philosophers of physics have discovered gauge theoriesarguably the paradigm of modern field physicsas a genuine topic for foundational and philosophical research. Incidentally, in the last couple of years interest from the philosophy of physics in structural realismin the eyes of its proponents the best suited realist position towards modern physicshas also raised. This paper tries to connect both topics and aims to show that structural realism gains further credence from an ontological analysis of gauge theoriesin particular (...) 

I argue against the currentlyprevalent view in philosophy of physics that algebraic quantum field theory is the correct framework for philosophy of quantum field theory and that "conventional" quantum field theory, of the sort used in mainstream particle physics, is not suitable for foundational study. In doing so, I defend the position that AQFT and CQFT, understood in an appropriate sense, ought to be understood as rival programs to resolve the mathematical and physical pathologies of renormalization theory, and that CQFT (...) 

Despite recent major advances in the neuroscience underlying cognition, the processes of its emergence and evolution are far from being understood. In our view, current interrelated concepts of mind; knowledge; epistemology; perception; cognition and information fail to reflect the real dynamics of mental processes, their ontology and their logic. It has become routine to talk about information in relation to these processes, but there is no consensus about its most relevant qualitative and functional properties. We present a theory of human (...) 

This paper examines the epistemological significance of the present situation of underdetermination in quantum mechanics. After analyzing this underdetermination at three levelsformal, ontological, and methodologicalthe paper considers implications for a number of variants of the thesis of scientific realism in fundamental physics and reassesses Lakatos‘ characterization of progress in physical theory in light of the present situation. Next, this paper considers the implications of underdetermination for Weinberg’s ‘‘dream of a final theory.’’ Finally, the paper concludes by suggesting how one might (...) 

I argue that algebraic quantum field theory (AQFT) permits an undisturbed view of the right ontology for fundamental physics, whereas standard (or Lagrangian) QFT offers different mutually incompatible ontologies.My claim does not depend on the mathematical inconsistency of standard QFT but on the fact that AQFT has the same concerns as ontology, namely categorical parsimony and a clearly structured hierarchy of entities. 