Perturbation theory for nonequilibrium quantum fields

1993 ◽  
Vol 71 (5-6) ◽  
pp. 262-268 ◽  
Author(s):  
Ian D. Lawrie
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Scalar Field ◽  
Real Time ◽  
Expanding Universe ◽  
Nonequilibrium Processes ◽  
Self Energy ◽  
Time Path ◽  
Renormalization Technique ◽  
Standard Perturbation Theory

Standard perturbation theory fails when applied to nonequilibrium processes. I explain why. To achieve sensible results, it is necessary to resum the absorptive parts of real-time self-energy corrections. Using the closed-time-path formalism, and in the context of scalar-field theory in an expanding universe, I show how a generalized renormalization technique can achieve this.

scholarly journals COSMOLOGY IN NONLINEAR BORN–INFELD SCALAR FIELD THEORY WITH NEGATIVE POTENTIALS

2007 ◽  
Vol 22 (12) ◽  
pp. 2173-2195 ◽  
Author(s):  
WEI FANG ◽  
H. Q. LU ◽  
Z. G. HUANG
Keyword(s):  
Field Theory ◽  
Scalar Field ◽  
Upper Bound ◽  
Expanding Universe ◽  
Scalar Field Theory ◽  
Stiff Matter ◽  
Ordinary Matter ◽  
Cosmological Solutions ◽  
Potential Parameters ◽  
Linear Scalar

The cosmological evolution in Nonlinear Born–Infeld (hereafter NLBI) scalar field theory with negative potentials was investigated. The cosmological solutions in some important evolutive epoches were obtained. The different evolutional behaviors between NLBI and linear (canonical) scalar field theory have been presented. A notable characteristic is that NLBI scalar field behaves as ordinary matter nearly the singularity while the linear scalar field behaves as "stiff" matter. We find that in order to accommodate current observational accelerating expanding universe the value of potential parameters |m| and |V0| must have an upper bound. We compare different cosmological evolutions for different potential parameters m, V0.

Reorganizing Finite Temperature Field Theory: Part I.: Scalar Field Theory

2001 ◽  
Vol 16 (supp01c) ◽  
pp. 1277-1280 ◽  
Author(s):  
Michael Strickland
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Temperature Field ◽  
Finite Temperature ◽  
Weak Coupling ◽  
Weak Coupling Limit ◽  
Finite Temperature Field Theory ◽  
Expansion Point ◽  
Perturbative Limit ◽  
Standard Perturbation Theory

I present a method for self-consistently including the effects of screening in finite-temperature field theory calculations. The method reproduces the perturbative limit in the weak-coupling limit and for intermediate couplings this method has much better convergence than standard perturbation theory. The method relies on a reorganization of perturbation theory accomplished by shifting the expansion point used to calculate quantum loop corrections. I will present results from a three-loop calculation within this formalism for scalar λϕ4.

scholarly journals GAP EQUATION IN SCALAR FIELD THEORY AT FINITE TEMPERATURE

1999 ◽  
Vol 14 (04) ◽  
pp. 257-266
Author(s):  
KRISHNENDU MUKHERJEE
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Scalar Field ◽  
Imaginary Part ◽  
Finite Temperature ◽  
Thermal Mass ◽  
Scalar Field Theory ◽  
Gap Equation ◽  
The Real

We investigate the two-loop gap equation for the thermal mass of hot massless g2ϕ4 theory and find that the gap equation itself has a nonzero finite imaginary part. This implies that it is not possible to find the real thermal mass as a solution of the gap equation beyond g2 order in perturbation theory. We have solved the gap equation and obtained the real and imaginary parts of the thermal mass which are correct up to g4 order in perturbation theory.

CALCULATIONAL ALGORITHM FOR THERMAL REACTION PROBABILITIES WITH FERMIONS

1993 ◽  
Vol 08 (10) ◽  
pp. 1729-1753 ◽  
Author(s):  
ASIDA NAOKI
Keyword(s):  
Field Theory ◽  
Statistical Mechanics ◽  
Real Time ◽  
Thermal Field ◽  
Thermal Reaction ◽  
Specific Time ◽  
Statistical Average ◽  
Thermal Vacuum ◽  
Self Energy ◽  
Feynman Rules

Calculational algorithm for thermal reaction probabilities including fermions is obtained. For this purpose, we faithfully follow the method of statistical mechanics, that is, taking explicitly the statistical average of the quantity under consideration. Our result is formulated in terms of Feynman rules of real time thermal field theory constructed on a specific time path. It is shown that the effect of the thermal vacuum bubble is of vital importance for analyzing diagrams with generalized self-energy parts.

Simplifying calculations in real time finite temperature field theory

2007 ◽  
Vol 85 (6) ◽  
pp. 671-677
Author(s):  
T Fugleberg ◽  
M E Carrington
Keyword(s):  
Field Theory ◽  
Temperature Field ◽  
Real Time ◽  
Finite Temperature ◽  
Quantum Electrodynamics ◽  
Previous Experience ◽  
Ward Identities ◽  
Finite Temperature Field Theory ◽  
Time Path ◽  
11.10 Wx

In this paper, we discuss a Mathematica program that we have written that calculates the integrand for amplitudes in the closed-time-path formulation of real-time finite-temperature field theory. The program is designed to be used by someone with no previous experience with Mathematica. It performs contractions over tensor indices that appear in real-time finite-temperature field theory and gives the result in the 1-2, Keldysh or R/A basis. As an illustration of this program, we discuss the calculation of all 3-point ward identities in finite-temperature quantum electrodynamics with full vertices. PACS Nos.: 11.10.Wx,11.15.-q

scholarly journals A first comparison of Kinetic Field Theory with Eulerian Standard Perturbation Theory

2021 ◽  
Vol 2021 (06) ◽  
pp. 035
Author(s):  
Elena Kozlikin ◽  
Robert Lilow ◽  
Felix Fabis ◽  
Matthias Bartelmann
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Kinetic Field ◽  
Standard Perturbation Theory

scholarly journals Perturbation theory and non-perturbative renormalization flow in scalar field theory at finite temperature

2007 ◽  
Vol 784 (1-4) ◽  
pp. 376-406 ◽  
Author(s):  
Jean-Paul Blaizot ◽  
Andreas Ipp ◽  
Ramón Méndez-Galain ◽  
Nicolás Wschebor
Keyword(s):  
Field Theory ◽  
Perturbation Theory ◽  
Scalar Field ◽  
Finite Temperature ◽  
Scalar Field Theory ◽  
Perturbative Renormalization
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