- 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

# Phase Transitions Near Two Dimensions

# Phase Transitions Near Two Dimensions

- Chapter:
- (p.733) 31 PHASE TRANSITIONS NEAR TWO DIMENSIONS
- Source:
- Quantum Field Theory and Critical Phenomena
- Author(s):
### JEAN ZINN-JUSTIN

- Publisher:
- Oxford University Press

This chapter discusses the generic *O*(*N*) non-linear σ-model. One property which plays an essential role is the UV asymptotic freedom of the σ-model in two dimensions. Some of its properties are expected to generalize to other asymptotically free models. In two dimensions, various fermion self-interacting models share this property. The symmetry which is then broken is the chiral symmetry which prevents explicit mass terms in the action. As in the case of the non-linear σ-model, IR divergences forbid the existence of a massless phase. One model of this kind can be defined in continuous dimensions, the Gross–Neveu (GN), a simpli cation of the Nambu–Jona-Lasinio model, which is studied in this chapter. It is renormalizable in two dimensions, and describes in perturbation theory only one phase, the phase with symmetry breaking. A model with the same symmetry can be identified, the Gross–Neveu–Yukawa (GNY) model which is renormalizable in four dimensions, and in which both phases can be reached already in the tree approximation. The study of these two models illustrates all the ideas and techniques developed in framework of the φ^{4} theory and the non-linear σ-models, that is RG equations near two and four dimensions, and large N expansion.

*Keywords:*
perturbation theory, non-linear model, massless phase, Gross–Neveu model, Gross–Neveu–Yukawa model, large N expansion

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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