scholarly journals Effective action for the Yukawa2 quantum field theory

1987 ◽  
Vol 108 (3) ◽  
pp. 437-467 ◽  
Author(s):  
A. Lesniewski
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Effective Action ◽  
Quantum Field

MESON-DIQUARK LOOP EXPANSION

1993 ◽  
Vol 08 (02) ◽  
pp. 277-300 ◽  
Author(s):  
M. LUTZ ◽  
J. PRASCHIFKA
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Effective Action ◽  
Degrees Of Freedom ◽  
Auxiliary Field ◽  
Quantum Field ◽  
Field Approach ◽  
Loop Expansion ◽  
Quark Models

We consider a general (nonlocal) four-fermion quantum field theory and show how the Cornwall-Jackiw-Tomboulis effective action can be systematically expanded in the number, η, of composite, bose loops. This is achieved by the introduction of auxiliary, bilocal fields which describe fermion-fermion and fermion-antifermion correlations. The η expansion can be understood as a generalization of the [Formula: see text] expansion and is of particular interest in quark models, for example, where the bilocal fields can be identified with meson and diquark degrees of freedom. Comparison with the usual loop (ħ) expansion reveals some unusual characteristics of the η expansion and throws light on recent studies of diquark degrees of freedom in which the auxiliary field approach is used.

Effective action of in Krein space quantization

2017 ◽  
Vol 95 (12) ◽  
pp. 1239-1241 ◽  
Author(s):  
B. Forghan ◽  
S. Razavi
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Effective Action ◽  
Regularization Method ◽  
Krein Space ◽  
Quantum Field ◽  
Kreĭn Space ◽  
Finite Solution ◽  
The One ◽  
Krein Space Quantization

The appearance of divergence creates computational issues in the process of calculating the one-loop effective action of [Formula: see text] in quantum field theory. In this paper, it is demonstrated that using Krein space quantization with Ford’s method of fluctuated metrics, divergence can be removed and that without using any traditional regularization method, it is possible to arrive at a finite solution for the effective action.

scholarly journals Singular structure of the QED effective action

2019 ◽  
Vol 49 ◽  
pp. 1960006
Author(s):  
B. A. Fayzullaev
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Perturbation Theory ◽  
Singular Perturbation ◽  
Effective Action ◽  
Electromagnetic Interaction ◽  
Perturbation Series ◽  
Singular Perturbation Theory ◽  
Quantum Field ◽  
Coupling Constant

The equations for the QED effective action derived in Ref. 3 are considered using singular perturbation theory. The effective action is divided into regular and singular (in coupling constant) parts. It is shown that expression for the regular part coincides with usual Feynman perturbation series over coupling constant, while the remainder has essential singularity at the vanishing coupling constant: [Formula: see text]. This means that in the frame of quantum field theory it is impossible “to switch off” electromagnetic interaction in general and pass on to “free electron”.

scholarly journals PARTICLE PRODUCTION ON HALF S-BRANE

2004 ◽  
Vol 19 (22) ◽  
pp. 3707-3728 ◽  
Author(s):  
J. KLUSOŇ
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Classical Solution ◽  
Effective Action ◽  
Particle Production ◽  
Large Time ◽  
Quantum Field ◽  
Fluctuation Field ◽  
Number Of Particles

In this paper we will study quantum field theory of fluctuation modes around the rolling tachyon solution on non-BPS D-brane effective action. The goal of this paper is to study particle production during the decay of non-BPS D-brane and explore possible relation with minisuperspace calculation. We find that the number of particles produced on half S-brane exponentially grows for large time which suggests that linearized approximation breaks down and also that backreaction of fluctuation field on classical solution should be taken into account.

scholarly journals COMMENTS ABOUT THE GEOMETRY OF NONLINEAR SIGMA MODELS

1987 ◽  
Vol 02 (06) ◽  
pp. 1763-1772 ◽  
Author(s):  
ROBERT COQUEREAUX
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Sigma Models ◽  
Effective Action ◽  
Quantum Field ◽  
Geometrical Meaning ◽  
Perturbative Quantum ◽  
Perturbative Quantum Field Theory ◽  
The One ◽  
Nonlinear Sigma Models

Geometrical aspects of several classes of σ models are studied. The geometrical meaning of perturbative quantum field theory is discussed in the content of nonlinear σ models. Results on the one-loop effective action are recovered and generalized.

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