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Locality, Localization, and the Particle Concept: Topics in the Foundations of Quantum Field Theory

Halvorson, Hans (2001) Locality, Localization, and the Particle Concept: Topics in the Foundations of Quantum Field Theory. [Preprint]

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      Abstract

      This dissertation reconsiders some traditional issues in the foundations of quantum mechanics in the context of relativistic quantum field theory (RQFT); and it considers some novel foundational issues that arise first in the context of RQFT. The first part of the dissertation considers quantum nonlocality in RQFT. Here I show that the generic state of RQFT displays Bell correlations relative to measurements performed in any pair of spacelike separated regions, no matter how distant. I also show that local systems in RQFT are "open" to influence from their environment, in the sense that it is generally impossible to perform local operations that would remove the entanglement between a local system and any other spacelike separated system. The second part of the dissertation argues that RQFT does not support a particle ontology -- at least if particles are understood to be localizable objects. In particular, while RQFT permits us to describe situations in which a determinate number of particles are present, it does not permit us to speak of the location of any individual particle, nor of the number of particles in any particular region of space. Nonetheless, the absence of localizable particles in RQFT does not threaten the integrity of our commonsense concept of a localized object. Indeed, RQFT itself predicts that descriptions in terms of localized objects can be quite accurate on the macroscopic level. The third part of the dissertation examines the so-called observer-dependence of the particle concept in RQFT -- that is, whether there are any particles present must be relativized to an observer's state of motion. Now, it is not uncommon for modern physical theories to subsume observer-dependent descriptions under a more general observer-independent description of some underlying state of affairs. However, I show that the conflicting accounts concerning the particle content of the field cannot be reconciled in this way. In fact, I argue that these conflicting accounts should be thought of as "complementary" in the same sense that position and momentum descriptions are complementary in elementary quantum mechanics.


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      Item Type: Preprint
      Keywords: Nonlocality, Bell's Theorem, Complementarity, Rindler Quanta
      Subjects: Specific Sciences > Physics > Fields and Particles
      Specific Sciences > Physics > Quantum Field Theory
      Depositing User: Hans Halvorson
      Date Deposited: 06 Aug 2001
      Last Modified: 07 Oct 2010 11:10
      Item ID: 346
      URI: http://philsci-archive.pitt.edu/id/eprint/346

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