Quantum Field Theory and Asymmetry of Causation

Jayne E. Thompson

Phil Dowe

I have claimed that it is profitable to distinguish three key questions about causation. The first question, what are causal processes and interactions? , was addressed in Chapter 5. The second question, what is the connection between causes and effects? , was addressed in Chapter 7.The third question, what makes a cause different from an effect? , has not been addressed, and it is to that task that we turn in the present chapter. The question of the directionality and asymmetry of causation has long been an important ingredient in philosophical discussions of causation, although perhaps Reichenbach (1991) was the first to truly appreciate the significance of the question. It is certainly an aspect of folk intuitions. Many philosophers have held that an adequate analysis of causality should provide an explanation or account of causal asymmetry. On the other hand, it is precisely this aspect of causation that is the most common target for elimination from empirical accounts. This chapter looks at the ability of 'process' theories of causality to provide such an account, granting certain constraints. The major constraint, or premise, in the following analysis is the assumption that quantum mechanics reveals the presence of backwards-in-time causation. Thus, in the first instance, the argument presented here will not convince those who hold that there can be no backwards causation. However, I derive an empirical prediction, which, if confirmed, would give those sceptical about backwards causation reason to think again. The chapter begins with an analysis of some of the formal properties of causation. This is followed by a nontechnical presentation of the famous difficulties associated with Bell phenomena in quantum mechanics, and the backwards-in-time solution to those difficulties.

P. N. Kaloyerou

Jakob Sprickerhof

In this dissertation, I will argue that quantum field theory can be interpreted as a description of causal interactions. I will first discuss previous theories of physical causation, and come to the conclusion that they are inapplicable in quantum field theory. As a consequence, I will start to develop a new theory of causation by first analysing the concept ‘causation’ into the most basic and widely shared intuitions, in order to find out later whether these intuitions can be reduced to physics. I will then have a closer look on the intuition that causation is a directed relation, which is commonly regarded as incompatible with the symmetries of physics. I will present a new argument to the effect that causation and quantum field theory are compatible with respect to the directionality of causation. After that, I will analyse the theoretical description of interactions in quantum field theory, and in particular group structure, locality and local conservation laws will crystallise as the central concepts that a causal interpretation might be based on. Subsequently, I will discuss and present replies to what I believe are the most relevant objections to a causal interpretation of physics, namely, Haag’s theorem, the measurement problem and entanglement. In the final chapter of this dissertation, I will conjoin the results of the previous chapters to a new theory of causation for quantum field theory. The main result will be that a causal process is a quantum field theoretical interaction, i.e., the exchange of energy from an initial to a final state via a force.

Yuichiro Kitajima

The basic idea of interventionist theories of causation is this: X causes Y iff there is a possible intervention on X for Y , and if the value of X were changed as a result of that intervention, then the value of Y would change.These theories are subdivided into reductive and non-reductive accounts.Reductive accounts, advanced by Menzies and Price (1993), reduce the notion of causation to a non-causal notion of intervention, while according to non-reductive accounts advanced by Woodward (2003), such a reduction is not possible.In the present paper, I investigate causation in algebraic quantum field theory from Woodward's point of view.I define the necessary condition for no causal relationship between the local algebras associated with two spacelike separated region, and show that this condition always holds under the usual axioms of algebraic quantum field theory.

Kalervo V. Laurikainen