scholarly journals Composite operator approach to dynamical mass generation in the (2 + 1)-dimensional Gross–Neveu model

2021 ◽  
Author(s):  
T. G. Khunjua ◽  
K. G. Klimenko ◽  
R. N. Zhokhov
Keyword(s):  
Effective Action ◽  
Phase Structure ◽  
Coupling Constant ◽  
Operator Approach ◽  
Mass Generation ◽  
Dynamical Mass ◽  
Cutoff Parameter ◽  
First Order ◽  
Bare Coupling Constant ◽  
Gross Neveu Model

Using a nonperturbative approach based on the Cornwall–Jackiw–Tomboulis (CJT) effective action [Formula: see text] for composite operators, the phase structure of the simplest massless [Formula: see text]-dimensional Gross–Neveu model is investigated. We have calculated [Formula: see text] in the first-order of the bare coupling constant [Formula: see text] and have shown that there exist three different specific dependences of [Formula: see text] on the cutoff parameter [Formula: see text], and in each case, the effective action and its stationarity equations have been obtained. The solutions of these equations correspond to the fact that three different masses of fermions can arise dynamically and, respectively, three different nontrivial phases can be observed in the model.

scholarly journals About renormalized effective action for the Yang-Mills theory in four-dimensional space-time

2018 ◽  
Vol 191 ◽  
pp. 06001
Author(s):  
A.V. Ivanov
Keyword(s):  
Infinite Series ◽  
Effective Action ◽  
Dimensional Space ◽  
Space Time ◽  
Coupling Constant ◽  
Asymptotic Approach ◽  
Yang Mills ◽  
Dimensional Space Time ◽  
Bare Coupling Constant ◽  
Renormalization Theory

This work is related to the asymptotic approach in the renormalization theory and its problems. As the main example, the Yang-Mills theory in four-dimensional space-time is considered. It has been shown earlier [16] that using the asymptotic of the bare coupling constant one can find an expression for the renormalized effective action, however, this formula has problems (divergence ln " and infinite series). This work shows the relation of these values and provides an answer for the renormalized effective action.

scholarly journals NAMBU-JONA-LASINIO MODEL IN CURVED SPACE-TIME

1993 ◽  
Vol 08 (22) ◽  
pp. 2117-2123 ◽  
Author(s):  
T. INAGAKI ◽  
T. MUTA ◽  
S.D. ODINTSOV
Keyword(s):  
Proper Time ◽  
Space Time ◽  
Leading Order ◽  
Coupling Constant ◽  
Normal Coordinate ◽  
Dynamical Mass ◽  
Curved Space ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The phase structure of Nambu-Jona-Lasinio model with N-component fermions in curved space-time is studied in the leading order of the 1/N expansion. The effective potential for composite operator [Formula: see text] is calculated by using the normal coordinate expansion in the Schwinger proper-time method. The existence of the first order phase transition caused by the change of the space-time curvature is confirmed and the dynamical mass of the fermion is calculated as a simultaneous function of the curvature and the four-fermion coupling constant. The phase diagram in the curvature and the coupling constant is obtained.

scholarly journals Two-loop mass anomalous dimension in reduced quantum electrodynamics and application to dynamical fermion mass generation

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
S. Metayer ◽  
S. Teber
Keyword(s):  
Quantum Electrodynamics ◽  
Anomalous Dimension ◽  
Dimensional Space ◽  
Quantitative Agreement ◽  
Fermion Mass ◽  
Coupling Constant ◽  
Mass Generation ◽  
Perfect Agreement ◽  
Dynamical Mass ◽  
Gauge Invariant

Abstract We consider reduced quantum electrodynamics ($$ {\mathrm{RQED}}_{d_{\gamma },{d}_e} $$ RQED d γ , d e ) a model describing fermions in a de-dimensional space-time and interacting via the exchange of massless bosons in dγ-dimensions (de ≤ dγ). We compute the two-loop mass anomalous dimension, γm, in general $$ {\mathrm{RQED}}_{4,{d}_e} $$ RQED 4 , d e with applications to RQED4,3 and QED4. We then proceed on studying dynamical (parity-even) fermion mass generation in $$ {\mathrm{RQED}}_{4,{d}_e} $$ RQED 4 , d e by constructing a fully gauge-invariant gap equation for $$ {\mathrm{RQED}}_{4,{d}_e} $$ RQED 4 , d e with γm as the only input. This equation allows for a straightforward analytic computation of the gauge-invariant critical coupling constant, αc, which is such that a dynamical mass is generated for αr> αc, where αr is the renormalized coupling constant, as well as the gauge-invariant critical number of fermion flavours, Nc, which is such that αc → ∞ and a dynamical mass is generated for N < Nc. For RQED4,3, our results are in perfect agreement with the more elaborate analysis based on the resolution of truncated Schwinger-Dyson equations at two-loop order. In the case of QED4, our analytical results (that use state of the art five-loop expression for γm) are in good quantitative agreement with those obtained from numerical approaches.

scholarly journals Supergraph calculation of one-loop divergences in higher-derivative 6D SYM theory

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
I. L. Buchbinder ◽  
E. A. Ivanov ◽  
B. S. Merzlikin ◽  
K. V. Stepanyantz
Keyword(s):  
Effective Action ◽  
A Priori ◽  
Coupling Constant ◽  
Harmonic Superspace ◽  
Classical Action ◽  
Higher Derivative ◽  
Component Approach ◽  
Dimensionless Coupling ◽  
The One ◽  
Dimensionless Coupling Constant

Abstract We apply the harmonic superspace approach for calculating the divergent part of the one-loop effective action of renormalizable 6D, $$ \mathcal{N} $$ N = (1, 0) supersymmetric higher-derivative gauge theory with a dimensionless coupling constant. Our consideration uses the background superfield method allowing to carry out the analysis of the effective action in a manifestly gauge covariant and $$ \mathcal{N} $$ N = (1, 0) supersymmetric way. We exploit the regularization by dimensional reduction, in which the divergences are absorbed into a renormalization of the coupling constant. Having the expression for the one-loop divergences, we calculate the relevant β-function. Its sign is specified by the overall sign of the classical action which in higher-derivative theories is not fixed a priori. The result agrees with the earlier calculations in the component approach. The superfield calculation is simpler and provides possibilities for various generalizations.

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