scholarly journals COMMENT ON FERMION PROPAGATOR IN REAL-TIME QUANTUM-FIELD THEORY AT FINITE TEMPERATURE AND DENSITY

2002 ◽  
Vol 17 (05) ◽  
pp. 303-308 ◽  
Author(s):  
A. NIÉGAWA
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Green Function ◽  
Finite Temperature ◽  
Standard Form ◽  
Quark Propagator ◽  
The Other ◽  
Quantum Field ◽  
Fermion Propagator ◽  
Time Quantum

Two forms are available for the fermion propagator at finite temperature and density. It is shown that, when one deals with a diquark-condensation-operator inserted Green function in hot and dense QCD, the standard form of the quark propagator does not work. On the other hand, another form of the quark propagator does work.

Momentum space techniques for curved space–time quantum field theory

1979 ◽  
Vol 367 (1728) ◽  
pp. 123-141 ◽  
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Momentum Space ◽  
Nuclear Physics ◽  
Space Time ◽  
Coordinate Space ◽  
Quantum Field ◽  
Curved Space ◽  
Time Quantum ◽  
Space Formulation

A momentum space formulation of curved space–time quantum field theory is presented. Such a formulation allows the riches of momentum space calculational techniques already existing in nuclear physics to be exploited in the application of quantum field theory to cosmology and astrophysics. It is demonstrated that one such technique can allow exact, or very accu­rate approximate, results to be obtained in cases which are intractable in coordinate space. An efficient method of numerical solution is also described.

Quantum field theory (QFT) at finite temperature: Equilibrium properties

2021 ◽  
pp. 786-830
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Phase Transitions ◽  
High Temperature ◽  
Dimensional Reduction ◽  
Finite Temperature ◽  
Finite Size ◽  
Quantum Field ◽  
Statistical Field ◽  
Statistical Field Theory

Some equilibrium properties in statistical quantum field theory (QFT), that is, relativistic QFT at finite temperature are reviewed. Study of QFT at finite temperature is motivated by cosmological problems, high energy heavy ion collisions, and speculations about possible phase transitions, also searched for in numerical simulations. In particular, the situation of finite temperature phase transitions, or the limit of high temperature (an ultra-relativistic limit where the temperature is much larger than the physical masses of particles) are discussed. The concept of dimensional reduction emerges, in many cases, statistical properties of finite-temperature QFT in (1, d − 1) dimensions can be described by an effective classical statistical field theory in (d − 1) dimensions. Dimensional reduction generalizes a property already observed in the non-relativistic example of the Bose gas, and indicates that quantum effects are less important at high temperature. The corresponding technical tools are a mode-expansion of fields in the Euclidean time variable, singling out the zero modes of boson fields, followed by a local expansion of the resulting (d − 1)-dimensional effective field theory (EFT). Additional physical intuition about QFT at finite temperature in (1, d−1) dimensions can be gained by considering it as a classical statistical field theory in d dimensions, with finite size in one dimension. This identification makes an analysis of finite temperature QFT in terms of the renormalization group (RG), and the theory of finite-size effects of the classical theory, possible. These ideas are illustrated with several simple examples, the φ4 field theory, the non-linear σ-model, the Gross–Neveu model and some gauge theories.

scholarly journals The relation between quantum and classical field theory with a classical source

2020 ◽  
Vol 476 (2243) ◽  
pp. 20200656
Author(s):  
S. A. Fulling ◽  
A. G. S. Landulfo ◽  
G. E. A. Matsas
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Classical Field Theory ◽  
Classical Field ◽  
Quantum Field ◽  
Schwarzschild Solution ◽  
Classical Source ◽  
Time Quantum ◽  
Perturbative Quantum ◽  
Classical Picture

Classical field theory is about fields and how they behave in space–time. Quantum field theory, in practice, usually seems to be about particles and how they scatter. Nevertheless, classical fields must emerge from quantum field theory in appropriate limits, and Michael Duff showed how this happens for the Schwarzschild solution in perturbative quantum gravity. In a series of papers, we and others have shown how classical radiation from an accelerated charge emerges from quantum field theory when the Unruh thermal effect is taken into account. Here, we sharpen those conclusions by showing that, even at finite times, the quantum picture is meaningful and is in close agreement with the classical picture.

scholarly journals Galilean covariance, Casimir effect and Stefan–Boltzmann law at finite temperature

2017 ◽  
Vol 32 (16) ◽  
pp. 1750094 ◽  
Author(s):  
S. C. Ulhoa ◽  
A. F. Santos ◽  
Faqir C. Khanna
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Finite Temperature ◽  
Temperature Effects ◽  
Casimir Effect ◽  
Quantum Field ◽  
Covariant Quantum ◽  
Thermo Field Dynamics ◽  
Boltzmann Law ◽  
Galilean Covariance

The Galilean covariance, formulated in 5-dimensions space, describes the nonrelativistic physics in a way similar to a Lorentz covariant quantum field theory being considered for relativistic physics. Using a nonrelativistic approach the Stefan–Boltzmann law and the Casimir effect at finite temperature for a particle with spin zero and 1/2 are calculated. The thermo field dynamics is used to include the finite temperature effects.

THE CLASSICAL HARMONIC OSCILLATOR ON GALOIS AND P-ADIC FIELDS

1989 ◽  
Vol 04 (09) ◽  
pp. 2211-2233 ◽  
Author(s):  
YANNICK MEURICE
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Difference Equation ◽  
Harmonic Oscillator ◽  
Continuum Limit ◽  
The Other ◽  
Quantum Field ◽  
Real Numbers ◽  
Technical Tool ◽  
Classical Motion

Starting from a difference equation corresponding to the harmonic oscillator, we discuss various properties of the classical motion (cycles, conserved quantity, boundedness, continuum limit) when the dynamical variables take their values on Galois or p-adic fields. We show that these properties can be applied as a technical tool to calculate the motion on the real numbers. On the other hand, we also give an example where the motions over Galois and p-adic fields have a direct physical interpretation. Some perspectives for quantum field theory and strings are briefly discussed.

REGULARIZATION OF GENERAL MULTIDIMENSIONAL EPSTEIN ZETA-FUNCTIONS

1989 ◽  
Vol 01 (01) ◽  
pp. 113-128 ◽  
Author(s):  
E. ELIZALDE ◽  
A. ROMEO
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Partition Function ◽  
Zeta Function ◽  
Finite Temperature ◽  
Casimir Effect ◽  
Zeta Functions ◽  
Quantum Field ◽  
Type Formula

We study expressions for the regularization of general multidimensional Epstein zeta-functions of the type [Formula: see text] After reviewing some classical results in the light of the extended proof of zeta-function regularization recently obtained by the authors, approximate but very quickly convergent expressions for these functions are derived. This type of analysis has many interesting applications, e.g. in any quantum field theory defined in a partially compactified Euclidean spacetime or at finite temperature. As an example, we obtain the partition function for the Casimir effect at finite temperature.

Sign in / Sign up

Export Citation Format

Share Document