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The $\mathscr {P}(\varphi )_2$ Model on de Sitter Space

About this Title

João C. A. Barata, Christian D. Jäkel and Jens Mund

Publication: Memoirs of the American Mathematical Society
Publication Year: 2023; Volume 281, Number 1389
ISBNs: 978-1-4704-5548-4 (print); 978-1-4704-7322-8 (online)
DOI: https://doi.org/10.1090/memo/1389
Published electronically: January 3, 2023
Keywords: De Sitter space, unitary irreducible representations, Fourier–Helgason transformation, (constructive) quantum field theory

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Table of Contents

Chapters

  • List of Symbols
  • Preface

1. De Sitter space

  • 1. De Sitter space as a Lorentzian manifold
  • 2. Space-time symmetries
  • 3. Induced representations for the Lorentz group
  • 4. Harmonic analysis on the hyperboloid

2. Free quantum fields

  • 5. Classical field theory
  • 6. Quantum one-particle structures
  • 7. Local algebras for the free field

3. Interacting quantum fields

  • 8. The interacting vacuum
  • 9. The interacting representation of $SO(1,2)$
  • 10. Local algebras for the interacting field
  • 11. The equations of motion and the stress-energy tensor
  • 12. Summary
  • A. A local flat tube theorem
  • B. One particle structures
  • C. Sobolev spaces on the circle and on the sphere
  • D. Some identities involving Legendre functions

Abstract

In 1975 Figari, Høegh-Krohn and Nappi constructed the ${\mathscr P}(\varphi )_2$ model on the de Sitter space. Here we complement their work with new results, which connect this model to various areas of mathematics. In particular,

  • [$i.)$] we discuss the causal structure of de Sitter space and the induces representations of the Lorentz group. We show that the UIRs of $SO_0(1,2)$ for both the principal and the complementary series can be formulated on Hilbert spaces whose functions are supported on a Cauchy surface. We describe the free classical dynamical system in both its covariant and canonical form, and present the associated quantum one-particle KMS structures in the sense of Kay (1985). Furthermore, we discuss the localisation properties of one-particle wave functions and how these properties are inherited by the algebras of local observables.
  • [$ii.)$] we describe the relations between the modular objects (in the sense of Tomita-Takesaki theory) associated to wedge algebras and the representations of the Lorentz group. We connect the representations of SO(1,2) to unitary representations of $SO(3)$ on the Euclidean sphere, and discuss how the ${\mathscr P}(\varphi )_2$ interaction can be represented by a rotation invariant vector in the Euclidean Fock space. We present a novel Osterwalder-Schrader reconstruction theorem, which shows that physical infrared problems are absent on de Sitter space. As shown in Figari, Høegh-Krohn, and Nappi (1975), the ultraviolet problems are resolved just like on flat Minkowski space. We state the Haag–Kastler axioms for the ${\mathscr P}(\varphi )_2$ model and we explain how the generators of the boosts and the rotations for the interacting quantum field theory arise from the stress-energy tensor. Finally, we show that the interacting quantum fields satisfy the equations of motion in their covariant form.
  • In summary, we argue that the de Sitter ${\mathscr P}(\varphi )_2$ model is the simplest and most explicit relativistic quantum field theory, which satisfies basic expectations, like covariance, particle creation, stability and finite speed of propagation.

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