Quantum Field Theory (QFT) is the mathematical and conceptual framework for contemporary elementary particle physics. In a rather informal sense QFT is the extension of quantum mechanics (QM), dealing with particles, over to fields, i.e. systems with an infinite number of degrees of freedom. (See the entry on quantum mechanics.) In the last few years QFT has become a more widely discussed topic in philosophy of science, with questions ranging from methodology and semantics to ontology. QFT taken seriously in its (...) metaphysical implications seems to give a picture of the world which is at variance with central classical conceptions of particles and fields, and even with some features of QM. -/- The following sketches how QFT describes fundamental physics and what the status of QFT is among other theories of physics. Since there is a strong emphasis on those aspects of the theory that are particularly important for interpretive inquiries, it does not replace an introduction to QFT as such. One main group of target readers are philosophers who want to get a first impression of some issues that may be of interest for their own work, another target group are physicists who are interested in a philosophical view upon QFT. (shrink)

Eventually, Kuhlmann proposes a dispositional trope ontology, according to which particularized properties and not things are the most basic entities.

Advocates of the New Mechanicism in philosophy of science argue that scientific explanation often consists in describing mechanisms responsible for natural phenomena. Despite its successes, one might think that this approach does not square with the ontological strictures of quantum mechanics. New Mechanists suppose that mechanisms are composed of objects with definite properties, which are interconnected via local causal interactions. Quantum mechanics calls these suppositions into question. Since mechanisms are hierarchical it appears that even macroscopic mechanisms must supervene on a (...) set of “objects” that behave non-classically. In this paper we argue, in part by appeal to the theory of quantum decoherence, that the universal validity of quantum mechanics does not undermine neo-mechanistic ontological and explanatory claims as they occur within in classical domains. Additionally, we argue that by relaxation of certain classical assumptions, mechanistic explanatory strategies can sometimes be carried over into the quantum domain. (shrink)

Quantum field theory provides the framework for many fundamental theories in modern physics, and over the last few years there has been growing interest in its historical and philosophical foundations. This anthology on the foundations of QFT brings together 15 essays by well-known researchers in physics, the philosophy of physics, and analytic philosophy.Many of these essays were first presented as papers at the conference?Ontological Aspects of Quantum Field Theory?, held at the Zentrum fr interdisziplin„re Forschung, Bielefeld, Germany. The essays contain (...) cutting-edge work on ontological aspects of QFT, including: the role of measurement and experimental evidence, corpuscular versus field-theoretic interpretations of QFT, the interpretation of gauge symmetry, and localization.This book is ideally suited to anyone with an interest in the foundations of quantum physics, including physicists, philosophers and historians of physics, as well as general readers interested in philosophy or science. (shrink)

Agent-based models derive the behavior of artificial socio-economic entities computationally from the actions of a large number of agents. One objection is that highly idealized ABMs fail to represent the real world in any reasonable sense. Another objection is that they at best show how observed patterns may have come about, because simulations are easy to produce and there is no evidence that this is really what happens. Moreover, different models may well yield the same result. I will rebut these (...) objections by focusing on an often neglected, but crucial function of ABMs. Building on Gelfert’s account of the exploratory uses of scientific models I show that, in the absence of an accepted underlying theory, successful ABMs lend inductive support to assumptions concerning certain structural feutures of the behavioral rules employed. One core step towards this goal is what I call multiple-model robustness analysis. (shrink)

Large changes of financial market prices without exogenous causes deviate significantly from the Gaussian behavior of random variables. This indicates that financial markets should be treated as complex systems, for which nonlinear interactions of its subunits/agents are crucial. I focus on how the complex systems perspective impacts the notion of explanations in economics. The mechanistic model seems to fit the bill, but problems surface on closer scrutiny. One characteristic of complex systems is that their behavior is surprisingly independent from microscopic (...) details. Thus, mechanistic explanations in the microreductionist manner seem unavailable. Despite these conflicts, I defend a modified structural mechanistic approach. (shrink)

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.

In recent debates mechanisms are often discussed in the context of ‘complex systems’ which are understood as having a complicated compositional structure. I want to draw the attention to another, radically different kind of complex system, in fact one that many scientists regard as the only genuine kind of complex system. Instead of being compositionally complex these systems rather exhibit highly non-trivial dynamical patterns on the basis of structurally simple arrangements of large numbers of non-linearly interacting constituents. The characteristic dynamical (...) patterns in what I call “dynamically complex systems” arise from the interaction of the system’s parts largely irrespective of many properties of these parts. Dynamically complex systems can exhibit surprising statistical characteristics, the robustness of which calls for an explanation in terms of underlying generating mechanisms. However, I want to argue, dynamically complex systems are not sufficiently covered by the available conceptions of mechanisms. I will explore how the notion of a mechanism has to be modified to accommodate this case. Moreover, I will show under which conditions the widespread, if not inflationary talk about mechanisms in complex systems stretches the notion of mechanisms beyond its reasonable limits and is no longer legitimate. (shrink)

Philosophy of physics is a small but thriving research field situated at the intersection between the natural sciences and the humanities. However, what exactly distinguishes philosophy of physics from physics is rarely made explicit in much depth. We provide a detailed analysis in the form of eleven theses, delineating both the nature of the questions asked in philosophy of physics and the methodology with which they are addressed.

Dieses Buch liefert dem Leser eine aktuelle und fundierte Einführung in die Philosophie der Quantenphysik. Obwohl sich die Quantentheorie durch spektakuläre empirische Erfolge auszeichnet, wird bis heute kontrovers diskutiert, wie sie zu verstehen ist. In diesem Werk geben die Autoren einen Überblick über die zahlreichen philosophischen Herausforderungen: Verletzen Quantenobjekte das Prinzip der Kausalität? Sind gleichartige Teilchen ununterscheidbar und daher keine Individuen? Behalten Quantenobjekte in der zeitlichen Entwicklung ihre Identität? Wie verhält sich ein zusammengesetztes Quantensystem zu seinen Teilen? Diese Fragen werden (...) im Rahmen verschiedener Deutungsansätze der Quantentheorie diskutiert. Ein Ausblick in die Quantenfeldtheorie verschärft das Hauptproblem der Nichtlokalität. Philosophie der Quantenphysik richtet sich an Philosophen mit Interesse für Physik, macht Physiker mit den philosophischen Fragen ihres Faches vertraut und liefert Anregungen für den gymnasialen Physik-Unterricht. Das Buch schließt damit eine Lücke zwischen populären Einführungen und spezialisierten Monografien zur Philosophie der Quantenphysik. In der vorliegenden zweiten Auflage wurde das Kapitel zu Verschränkung und Nicht-Lokalität deutlich erweitert und jedes Kapitel mit Übungsaufgaben und Musterlösungen ergänzt. (shrink)

This book provides a thorough and up-to-date introduction to the philosophy of quantum physics. Although quantum theory is renowned for its spectacular empirical successes, controversial discussion about how it should be understood continue to rage today. In this volume, the authors provide an overview of its numerous philosophical challenges: Do quantum objects violate the principle of causality? Are particles of the same type indistinguishable and therefore not individual entities? Do quantum objects retain their identity over time? How does a compound (...) quantum system relate to its parts? These questions are answered here within different interpretational approaches to quantum theory. Finally, moving to Quantum Field Theory, we find that the problem of non-locality is exacerbated. Philosophy of quantum physics is aimed at philosophers with an interest in physics, while also serving to familiarize physicists with many of the essential philosophical questions of their subject. (shrink)

Financial theory is in trouble. Market crashes and high volatility are only too familiar to everyone, although the standard theories predict that they hardly ever occur. According to the well-known and (partly due to its simplicity) still widely used random-walk model, the probabilities for price changes of, say, stocks should result in a Gaussian distribution. However, experience tells us that large changes occur far more often than ‘allowed’ by a Gaussian distribution. New models are needed which lead to realistic probability (...) distributions. ‘Econophysicists’ are particularly active in this field by constructing microscopic models of financial markets on the basis of various ideas and tools from physics. But in which sense do these models contribute scientific explanations? In this paper I will investigate what and how one exemplary econophysics model explains. (shrink)

Dieses Buch liefert dem Leser eine aktuelle und fundierte Einführung in die Philosophie der Quantenphysik. Obwohl sich die Quantentheorie durch spektakuläre empirische Erfolge auszeichnet, wird bis heute kontrovers diskutiert, wie sie zu verstehen ist. In diesem Werk geben die Autoren einen Überblick über die zahlreichen philosophischen Herausforderungen: Verletzen Quantenobjekte das Prinzip der Kausalität? Sind gleichartige Teilchen ununterscheidbar und daher keine Individuen? Behalten Quantenobjekte in der zeitlichen Entwicklung ihre Identität? Wie verhält sich ein zusammengesetztes Quantensystem zu seinen Teilen? Diese Fragen werden (...) im Rahmen verschiedener Deutungsansätze der Quantentheorie diskutiert. Ein Ausblick in die Quantenfeldtheorie verschärft das Hauptproblem der Nichtlokalität. Philosophie der Quantenphysik richtet sich an Philosophiestudierende mit Interesse für Physik, macht Physikerinnen und Physiker mit den philosophischen Fragen ihres Faches vertraut und liefert Lehramtsstudierenden und Lehrern Anregungen für den gymnasialen Physik-Unterricht. Das Buch schließt damit eine Lücke zwischen populären Einführungen und spezialisierten Monografien zur Philosophie der Quantenphysik im deutschsprachigen Lehrbuchmarkt. In der vorliegenden zweiten Auflage wurde das Kapitel zu Verschränkung und Nicht-Lokalität deutlich erweitert und jedes Kapitel mit Übungsaufgaben und Musterlösungen ergänzt. cord friebezurzeit="" vertretung="" der="" professur="" für="" analytische="" philosophie="" an="" universität="" des="" saarlandes.p. (shrink)

Die folgende Chronologie legt den Fokus auf die Grundlagen und Deutungen der Quantenphysik, sie ist keine Geschichte der Quantenphysik im Ganzen, insbesondere finden die speziellen Entwicklungen der Quantenfeldtheorie und der sich daraus entwickelnden Teilchenphysik keine Berücksichtigung.

Viele ihrer philosophischen Probleme teilt die Quantenfeldtheorie mit der Quantenmechanik. Dazu gehören der Messprozess und die damit zusammenhängenden Interpretationsprobleme, zu denen die QFT kaum etwas Neues beiträgt. Auch die Frage, wie die Objekte, die die Theorie beschreibt, in den Raum eingebettet sind, wird schon in der Quantenmechanik diskutiert. Die neuen mathematischen Strukturen der QFT lassen allerdings auch neue Antworten erwarten, so dass die raumzeitliche Interpretation der Theorie ein wichtiges Thema wird. In diesem Kapitel werden die mathematischen Besonderheiten der QFT skizziert (...) und es wird gezeigt, dass dadurch sowohl eine Teilchen- wie auch eine Feldinterpretation ausgeschlossen wird. Zum Abschluss werden alternative Interpretationsansätze diskutiert. (shrink)