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3 results

Philosophy of Particle Physics

Philosophy of Particle Physics
  • Porter Williams
  • Published online:
    25 July 2023
    Print publication:
    24 August 2023
  • This Element offers an introduction to selected philosophical issues that arise in contemporary particle physics, aimed at philosophers who have limited prior exposure to quantum field theory. One the one hand, it critically surveys philosophical work on the representation of particles in quantum field theory, the formal machinery and conceptual implications of renormalization and renormalization group methods, and ontological and methodological questions raised by the use of effective field theory techniques in particle physics. On the other, it identifies topics in particle physics that have not yet received philosophical attention and sketches avenues for philosophical analysis of those topics. The primary aim of the Element is to provide philosophers of physics with an entry point into the literature on the philosophy of particle physics and identify interesting directions for future research for students and researchers alike.

  • 9 - Metric Correlations at One-Loop: In-In and Large N

  • from Part III - Stochastic Gravity
  • Bei-Lok B. Hu, University of Maryland, College Park, Enric Verdaguer, Universitat de Barcelona
  • Book:
    Semiclassical and Stochastic Gravity
    Published online:
    20 January 2020
    Print publication:
    05 March 2020, pp 317-336

  • Summary

    As a short introduction to this chapter we first briefly summarize the in-in or closed-time-path (CTP) functional formalism and evaluate the CTP effective action for a scalar field in Minkowski spacetime. We then consider N quantum matter fields interacting with the gravitational field assuming an effective field theory approach to quantum gravity and consider the quantization of metric perturbations around a semiclassical background in the CTP formalism. A suitable prescription is given to select an asymptotic initial vacuum state of the interacting theory; this prescription plays an important role in calculations in later chapters. We derive expressions for the two-point metric correlations, which are conveniently written in terms of the CTP effective action that results from integrating out the matter fields by rescaling the gravitational constant and performing a 1/N expansion. These correlations include loop corrections from matter fields but no graviton loops. This is achieved consistently in the 1/N expansion, and is illustrated in a simplified model of matter–gravity interaction.