- Title Pages
- Preface
- Acknowledgments
- General References
- 1 Algebraic Preliminaries
- 2 Euclidean Path Integrals In Quantum Mechanics
- 3 Path Integrals In Quantum Mechanics: Generalizations
- 4 Stochastic Differential Equations: Langevin, Fokker–Planck Equations
- 5 Path And Functional Integrals In Quantum Statistical Physics
- 6 Quantum Evolution: From Particles To Fields
- 7 Quantum Field Theory: Functional Methods and Perturbation Theory
- 8 Relativistic Fermions
- 9 Quantum Field Theory: Divergences and Regularization
- 10 Introduction to Renormalization Theory. Renormalization Group Equations
- 11 Dimensional Regularization, Minimal Subtraction: RG Functions
- 12 Renormalization Of Composite Operators. Short Distance Expansion
- 13 Symmetries And Renormalization
- 14 The Non-Linear σ-Model: An Example Of a Non-Linear Symmetry
- 15 General Non-Linear Models In Two Dimensions
- 16 St And Brs Symmetries, Stochastic Field Equations
- 17 From Langevin Equation To Supersymmetry
- 18 Abelian Gauge Theories
- 19 Non-Abelian Gauge Theories: Introduction
- 20 The Standard Model. Anomalies
- 21 Gauge Theories: Master Equation And Renormalization
- 22 Classical And Quantum Gravity. Riemannian Manifolds And Tensors
- 23 Critical Phenomena: General Considerations
- 24 Mean Field Theory For Ferromagnetic Systems
- 25 General Renormalization Group. The Critical Theory Near Dimension Four
- 26 Scaling Behaviour In The Critical Domain
- 27 Corrections to Scaling Behaviour
- 28 Non-Magnetic Systems and The (φ<sup>2</sup>)<sup>2</sup> Field Theory
- 29 Calculation Of Universal Quantities
- 30 The <i>O</i>(<i>N</i>) Vector Model For <i>N</i> Large
- 31 Phase Transitions Near Two Dimensions
- 32 Two-Dimensional Models and Bosonization Method
- 33 The <i>O</i>(2) Classical Spin Model In Two Dimensions
- 34 Critical Properties Of Gauge Theories
- 35 Uv Fixed Points In Quantum Field Theory
- 36 Critical Dynamics
- 37 Field Theory in a Finite Geometry: Finite Size Scaling
- 38 Quantum Field Theory At Finite Temperature: Equilibrium Properties
- 39 Instantons In Quantum Mechanics
- 40 Unstable Vacua In Quantum Field Theory
- 41 Degenerate Classical Minima And Instantons
- 42 Perturbation Series At Large Orders. Summation Methods
- 43 Multi-Instantons In Quantum Mechanics
- Index

# Quantum Evolution: From Particles To Fields

# Quantum Evolution: From Particles To Fields

- Chapter:
- (p.110) 6 QUANTUM EVOLUTION: FROM PARTICLES TO FIELDS
- Source:
- Quantum Field Theory and Critical Phenomena
- Author(s):
### JEAN ZINN-JUSTIN

- Publisher:
- Oxford University Press

To calculate scattering S-matrix elements, quantities relevant to Particle Physics, it is necessary to consider instead the quantum evolution operator in real time. This chapter begins by deriving the path integral representation of the evolution operator and the *S*-matrix in simple quantum mechanics. To illustrate the power of the formalism, it shows how to recover the perturbative expansion of the scattering amplitude, some semi-classical approximations, and the eikonal approximation. When the asymptotic states at large time are eigenstates of the harmonic oscillator, instead of free particles, the holomorphic formalism becomes useful. A simple generalization of the path integral of Section 5.1 leads to the corresponding path integral representation of the *S*-matrix. In the case of the Bose gas the evolution operator is then given by a holomorphic functional integral. Using the parallel formalism of Section 5.6, the chapter derives an analogous representation for the evolution operator of a system of non-relativistic fermions. It then begins the study of relativistic quantum field theory with the example of the self-coupled neutral scalar boson. It shows that the holomorphic formalism, in a form that extends the construction of Section 5.5 to relativistic real time evolution, leads to various representations of the *S*-matrix in terms of functional integrals. The chapter relates *S*-matrix elements to the continuation to real time of various kinds of euclidean correlation functions.

*Keywords:*
S-matrix, quantum evolution operator, functional integrals, quantum field theory, holomorphic formalism, quantum mechanics

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- Title Pages
- Preface
- Acknowledgments
- General References
- 1 Algebraic Preliminaries
- 2 Euclidean Path Integrals In Quantum Mechanics
- 3 Path Integrals In Quantum Mechanics: Generalizations
- 4 Stochastic Differential Equations: Langevin, Fokker–Planck Equations
- 5 Path And Functional Integrals In Quantum Statistical Physics
- 6 Quantum Evolution: From Particles To Fields
- 7 Quantum Field Theory: Functional Methods and Perturbation Theory
- 8 Relativistic Fermions
- 9 Quantum Field Theory: Divergences and Regularization
- 10 Introduction to Renormalization Theory. Renormalization Group Equations
- 11 Dimensional Regularization, Minimal Subtraction: RG Functions
- 12 Renormalization Of Composite Operators. Short Distance Expansion
- 13 Symmetries And Renormalization
- 14 The Non-Linear σ-Model: An Example Of a Non-Linear Symmetry
- 15 General Non-Linear Models In Two Dimensions
- 16 St And Brs Symmetries, Stochastic Field Equations
- 17 From Langevin Equation To Supersymmetry
- 18 Abelian Gauge Theories
- 19 Non-Abelian Gauge Theories: Introduction
- 20 The Standard Model. Anomalies
- 21 Gauge Theories: Master Equation And Renormalization
- 22 Classical And Quantum Gravity. Riemannian Manifolds And Tensors
- 23 Critical Phenomena: General Considerations
- 24 Mean Field Theory For Ferromagnetic Systems
- 25 General Renormalization Group. The Critical Theory Near Dimension Four
- 26 Scaling Behaviour In The Critical Domain
- 27 Corrections to Scaling Behaviour
- 28 Non-Magnetic Systems and The (φ<sup>2</sup>)<sup>2</sup> Field Theory
- 29 Calculation Of Universal Quantities
- 30 The <i>O</i>(<i>N</i>) Vector Model For <i>N</i> Large
- 31 Phase Transitions Near Two Dimensions
- 32 Two-Dimensional Models and Bosonization Method
- 33 The <i>O</i>(2) Classical Spin Model In Two Dimensions
- 34 Critical Properties Of Gauge Theories
- 35 Uv Fixed Points In Quantum Field Theory
- 36 Critical Dynamics
- 37 Field Theory in a Finite Geometry: Finite Size Scaling
- 38 Quantum Field Theory At Finite Temperature: Equilibrium Properties
- 39 Instantons In Quantum Mechanics
- 40 Unstable Vacua In Quantum Field Theory
- 41 Degenerate Classical Minima And Instantons
- 42 Perturbation Series At Large Orders. Summation Methods
- 43 Multi-Instantons In Quantum Mechanics
- Index