The priority of internal symmetries in particle physics

In this paper, I try to decipher the role of internal symmetries in the ontological maze of particle physics. The relationship between internal symmetries and laws of nature is discussed within the framework of “Platonic realism.” The notion of physical “structure” is introduced as representing a deeper ontological layer behind the observable world. I argue that an internal symmetry is a structure encompassing laws of nature. The application of internal symmetry groups to particle physics came about in two revolutionary steps. The first was the introduction of the internal symmetries of hadrons in the early 1960s. These global and approximate symmetries served as means of bypassing the dynamics. I argue that the realist could interpret these symmetries as ontologically prior to the hadrons. The second step was the gauge revolution in the 1970s, where symmetries became local and exact and were integrated with the dynamics. I argue that the symmetries of the second generation are fundamental in the following two respects: (1) According to the so-called “gauge argument,” gauge symmetry dictates the existence of gauge bosons, which determine the nature of the forces. This view, which has been recently criticized by some philosophers, is widely accepted in particle physics at least as a heuristic principle. (2) In view of grand unified theories, the new symmetries can be interpreted as ontologically prior to baryon matter.     

A partial elucidation of the gauge principle

The elucidation of the gauge principle “is the most pressing problem in current philosophy of physics” said Michael Redhead in 2003. This paper argues for two points that contribute to this elucidation in the context of Yang–Mills theories. (1) Yang–Mills theories, including quantum electrodynamics, form a class. They should be interpreted together. To focus on electrodynamics is potentially misleading. (2) The essential role of gauge and BRST symmetries is to provide a local field theory that can be quantized and would be equivalent to the quantization of the non-local reduced theory. If this is correct, the gauge symmetry is significant, not so much because it implies ontological consequences, but because it allows us to quantize theories that we would not be able to quantize otherwise. Thus, in the context of Yang–Mills theories, it is essentially a pragmatic principle. This does not seem to be the case for the gauge symmetry in general relativity.     

Mechanisms, principles, and Lorentz's cautious realism

I show that Albert Einstein's distinction between principle and constructive theories was predated by Hendrik A. Lorentz's equivalent distinction between mechanism- and principle-theories. I further argue that Lorentz's views toward realism similarly prefigure what Arthur Fine identified as Einstein's “motivational realism.”     

Why the Afshar experiment does not refute complementarity

A modified version of Young's experiment by Shahriar Afshar demonstrates that, prior to what appears to be a “which-way” measurement, an interference pattern exists. Afshar has claimed that this result constitutes a violation of the Principle of Complementarity. This paper discusses the implications of this experiment and considers how Cramer's Transactional Interpretation easily accommodates the result. It is also shown that the Afshar experiment is analogous in key respects to a spin one-half particle prepared as “spin up along x”, subjected to a nondestructive confirmation of that preparation, and post-selected in a specific state of spin along z. The terminology “which-way” or “which-slit” is critiqued; it is argued that this usage by both Afshar and his critics is misleading and has contributed to confusion surrounding the interpretation of the experiment. Nevertheless, it is concluded that Bohr would have had no more problem accounting for the Afshar result than he would in accounting for the aforementioned pre- and post-selection spin experiment, in which the particle's preparation state is confirmed by a nondestructive measurement prior to post-selection. In addition, some new inferences about the interpretation of delayed choice experiments are drawn from the analysis.     

The cosmological constant, the fate of the universe, unimodular gravity, and all that

The cosmological constant is back. Several lines of evidence point to the conclusion that either there is a positive cosmological constant or else the universe is filled with a strange form of matter (“quintessence”) that mimics some of the effects of a positive lambda. This paper investigates the implications of the former possibility. Two senses in which the cosmological constant can be a constant are distinguished: the capital Λ sense in which lambda is a universal constant on a par with the charge of the electron, and the lower case λ sense in which lambda is a humble constant of integration. The latter interpretation has been touted as the means to a solution to various problems in physics. These claims are critically examined with an eye to discerning the implications for philosophy of science and foundations of physics.     

The problem of time's arrow historico-critically reexamined

Responding to Hasok Chang's vision of the history and philosophy of science (HPS) as the continuation of science by other means, I illustrate the methods of HPS and their utility through a historico-critical examination of the problem of “time's arrow”, that is to say, the problem posed by the claim by Boltzmann and others that the temporal asymmetry of many physical processes and indeed the very possibility of identifying each of the two directions we distinguish in time must have a ground in the laws of nature. I claim that this problem has proved intractable chiefly because the standard mathematical representation of time employed in the formulation of the laws of nature “forgets” one of the connotations of the word ‘time’ as it is used in ordinary language and in experimental physics.     

Did Einstein prove E=mc2?

Although Einstein's name is closely linked with the celebrated relation E=mc² between mass and energy, a critical examination of the more than half dozen “proofs” of this relation that Einstein produced over a span of forty years reveals that all these proofs suffer from mistakes. Einstein introduced unjustified assumptions, committed fatal errors in logic, or adopted low-speed, restrictive approximations. He never succeeded in producing a valid general proof applicable to a realistic system with arbitrarily large internal speeds. The first such general proof was produced by Max Laue in 1911 (for “closed” systems with a time-independent energy–momentum tensor) and it was generalized by Felix Klein in 1918 (for arbitrary time-dependent “closed” systems).     

Energy conservation and supertasks

The most recent results in the dynamics of infinite systems of particles have shown there is no necessary connection between the performance of a deterministic supertask and the non-conservation of energy. Much more difficult to prove is the non-existence of any necessary connection between the performance of an indeterministic supertask and the non-conservation of energy; however, this paper does just that. So the requirement that energy be conserved does not mean we can exclude as “non-physical” either of the two major types of supertask considered to date. The paper also proposes, in this context, a “hidden variables method” to prove general results of compatibility in dynamics.     

Measuring constants of nature: confirmation and determination in piezoelectricity

Exact measurements are a central practice of modern physics. In certain cases, they are essential for determining values of coefficients, for confirming theories, and for detecting the existence of effects. The history of piezoelectricity at the end of the nineteenth century reveals two different methods of exact measurement: a mathematical versus an “artisanal” approach. In the former, a scientist first carried out the experiment and later employed mathematical methods to reduce error. In the latter, a scientist physically manipulated the experimental apparatus to bypass possible sources of error before its performance. These two approaches were related to German theoreticians and to French experimentalists, respectively. However, affiliation with a particular school rather than nationality was the decisive factor in the differences between the two approaches. Despite differences, adherents of both approaches sought to attain high precision and to eliminate even small experimental errors.This history exhibits the complexity and flexibility of experiments and their analysis. It supports the claim of the “New Experimentalism” that theory does not supply complete directions for practical experimental decisions. An example for this is found in the way an experimental error was discovered (after incorrect results had already been published) only by a comparison to an earlier experiment rather than to a theory.     

Introduction

The question of the existence of intelligent life on other worlds has never been a purely scientific one. Philosophical, religious and literary issues have been intertwined with scientific ones throughout the history of the “plurality of worlds” debate. This collection of papers in –Studies in History and Philosophy of Science– explores the interrelation of science, philosophy, religion and literature in debates about extraterrestrial life.     

Actants and enframing: Heidegger and Latour on technology

A central issue in the philosophy of technology concerns the relationship between technology and the conditions under which technology develops. Traditionally, two main accounts are given of this relationship. The social constructivist approach considers technology to be largely determined by “social” factors (e.g. military interests, economic policy). By contrast, technological determinism describes technology as self-determinative, and as following its own independent aim of greater efficiency. This paper discusses two alternatives to these conceptions of technology, namely, the accounts offered by Bruno Latour and Martin Heidegger. It examines their common theses that our present misunderstanding of technology is due to a continued commitment to the subject–object distinction. The paper further compares their accounts, which attempt to overcome this distinction, and argues that ultimately both authors fail to find a role for human beings that is consistent with their contention that we need to develop a less anthropocentric understanding of the world.     

Experiment versus mechanical philosophy in the work of Robert Boyle: a reply to Anstey and Pyle

We can distinguish ‘mechanical’ in the strict sense of the mechanical philosophers from ‘mechanical’ in the common sense. My claim is that Boyle's experimental science owed nothing to, and offered no support for, the mechanical philosophy in the strict sense. The attempts by my critics to undermine my case involve their interpreting ‘mechanical’ in something like the common sense. I certainly accept that Boyle's experimental science was productively informed by mechanical analogies, where ‘mechanical’ is interpreted in a common sense. But this leaves my original claim untouched and, in the main, unchallenged.     

Gauge theories and holisms

Those looking for holism in contemporary physics have focused their attention primarily on quantum entanglement. But some gauge theories arguably also manifest the related phenomenon of nonseparability. While the argument is strong for the classical gauge theory describing electromagnetic interactions with quantum “particles”, it fails in the case of general relativity even though that theory may also be formulated in terms of a connection on a principal fiber bundle. Anandan has highlighted the key difference in his analysis of a supposed gravitational analog to the Aharonov–Bohm effect. By contrast with electromagnetism in the original Aharonov–Bohm effect, gravitation is separable and exhibits no novel holism in this case. Whether the nonseparability of classical gauge theories of nongravitational interactions is associated with holism depends on what counts as the relevant part–whole relation. Loop representations of quantized gauge theories of nongravitational interactions suggest that these conclusions about holism and nonseparability may extend also to quantum theories of the associated fields.     

Weinberg's proof of the spin-statistics theorem

The aim of this paper is to offer a conceptual analysis of Weinberg's proof of the spin-statistics theorem by comparing it with Pauli's original proof and with the subsequent textbook tradition, which typically resorts to the dichotomy positive energy for half-integral spin particles/microcausality for integral-spin particles. In contrast to this tradition, Weinberg's proof does not directly invoke the positivity of the energy, but derives the theorem from the single relativistic requirement of microcausality. This seemingly innocuous difference marks an important change in the conceptual basis of quantum physics. Its historical, theoretical, and conceptual roots are here reconstructed. The link between Weinberg's proof and Pauli's original is highlighted: Weinberg's proof turns out to do justice to Pauli's anti-Dirac lines of thought. The work of Furry and Oppenheimer is also surveyed as a “third way” between the textbook tradition established by Pauli and Weinberg's approach.     

Localization and the interface between quantum mechanics, quantum field theory and quantum gravity II: The search of the interface between QFT and QG

The main topics of this second part of a two-part essay are some consequences of the phenomenon of vacuum polarization as the most important physical manifestation of modular localization. Besides philosophically unexpected consequences, it has led to a new constructive “outside-inwards approach” in which the pointlike fields and the compactly localized operator algebras which they generate only appear from intersecting much simpler algebras localized in noncompact wedge regions whose generators have extremely mild almost free field behavior.Another consequence of vacuum polarization presented in this essay is the localization entropy near a causal horizon which follows a logarithmically modified area law in which a dimensionless area (the area divided by the square of dR where dR is the thickness of a light-sheet) appears. There are arguments that this logarithmically modified area law corresponds to the volume law of the standard heat bath thermal behavior. We also explain the symmetry enhancing effect of holographic projections onto the causal horizon of a region and show that the resulting infinite dimensional symmetry groups contain the Bondi–Metzner–Sachs group. This essay is the second part of a partitioned longer paper.     

Subsystems and independence in relativistic microscopic physics

The analyzability of the universe into subsystems requires a concept of the “independence” of the subsystems, of which the relativistic quantum world supports many distinct notions which either coincide or are trivial in the classical setting. The multitude of such notions and the complex relations between them will only be adumbrated here. The emphasis of the discussion is placed upon the warrant for and the consequences of a particular notion of subsystem independence, which, it is proposed, should be viewed as primary and, it is argued, provides a reasonable framework within which to sensibly speak of relativistic quantum subsystems.     

The development of the Neurath principle: unearthing the Romantic link

Otto Neurath’s thoroughgoing anti-foundationalism is connected to the recognition that protocol sentences are not inviolable, that is they are fallible and their choice cannot be determined: ‘Poincaré, Duhem and others have adequately shown that even if we have agreed on the protocol statements, there is a not limited number of equally applicable, possible systems of hypotheses. We have extended this tenet of the uncertainty of systems of hypotheses to all statements, including protocol statements that are alterable in principle’ (Neurath, 1983, p. 105). Later historiography has called Neurath’s extension of Duhemian holism the Neurath principle. Based on a study of Neurath’s early works on the history of optics, the paper investigates a previously unnoticed influence on the development of this principle, Neurath’s reading of Goethe’s Theory of colours. The historical and polemical parts of Goethe’s tripartite book provided Neurath with ideal examples for the vertical extension of Duhem’s thesis to observation statements. Moreover, Goethe’s critique of the language of science and his views on the theory-ladenness of observation, as well as on the history of science show strong parallels to many of Neurath’s ideas. These demonstrate the existence of surprisingly direct textual links between Romantic views on science and the development of twentieth-century philosophy of science. Neurath’s usage of Goethe’s examples also indicates that the birth of the Neurath principle is more tightly connected to actual scientific practice than to theory-testing, and that by admitting the theory-ladenness of observation reports and fallibility of protocol statements Neurath does not throw empiricism overboard.     

Explaining Leibniz equivalence as difference of non-inertial appearances: Dis-solution of the Hole Argument and physical individuation of point-events

“The last remnant of physical objectivity of space–time” is disclosed in the case of a continuous family of spatially non-compact models of general relativity (GR). The physical individuation of point-events is furnished by the autonomous degrees of freedom of the gravitational field (viz., the Dirac observables) which represent—as it were—the ontic part of the metric field. The physical role of the epistemic part (viz. the gauge variables) is likewise clarified as embodying the unavoidable non-inertial aspects of GR. At the end the philosophical import of the Hole Argument is substantially weakened and in fact the Argument itself dissolved, while a specific four-dimensional holistic and structuralist view of space–time (called point-structuralism) emerges, including elements common to the tradition of both substantivalism and relationism. The observables of our models undergo real temporal change: this gives new evidence to the fact that statements like the frozen-time character of evolution, as other ontological claims about GR, are model dependent.