scholarly journals DYNAMICAL GENERATION OF THE GAUGED SU(2) LINEAR SIGMA MODEL

1995 ◽  
Vol 10 (03) ◽  
pp. 251-266 ◽  
Author(s):  
R. DELBOURGO ◽  
M. D. SCADRON
Keyword(s):  
Sigma Model ◽  
Decay Constant ◽  
Chiral Limit ◽  
Linear Sigma Model ◽  
Coupling Constant ◽  
Vector Coupling ◽  
Dynamical Generation ◽  
Meson Coupling ◽  
Quark Level ◽  
The Masses

The fermion and meson sectors of the quark-level SU(2) linear sigma model are dynamically generated from a meson–quark Lagrangian, with the quark (q) and meson (σ, π) fields all treated as elementary, having neither bare masses nor expectation values. In the chiral limit, the masses are predicted to be mq = fπg, mπ = 0, mσ = 2mq, and we also find that the quark–meson coupling is [Formula: see text], the three-meson coupling is [Formula: see text] and the four-meson coupling is λ = 2g2 = g′/fπ, where fπ ≃ 90 MeV is the pion decay constant and Nc = 3 is the color number. By gauging this model one can generate the couplings to the vector mesons ρ and A1, including the quark–vector coupling constant gρ = 2π, gρππ, gA1ρπ and the masses mρ ~ 700 MeV, [Formula: see text]; of course the vector and axial currents remain conserved throughout.

scholarly journals On the Dynamical Generation of Quark-Level-Linear-Sigma-Model-like Theories beyond one Loop

2008 ◽  
Author(s):  
Frieder Kleefeld ◽  
George Rupp ◽  
Eef van Beveren ◽  
Pedro Bicudo ◽  
Brigitte Hiller ◽  
...  
Keyword(s):  
Sigma Model ◽  
Linear Sigma Model ◽  
Dynamical Generation ◽  
Quark Level

PROCEDURE FOR GENERATING EQUATIONS IN LINEAR SIGMA MODEL

2011 ◽  
Vol 26 (14) ◽  
pp. 2327-2352 ◽  
Author(s):  
AMIR H. FARIBORZ
Keyword(s):  
Scattering Amplitudes ◽  
Sigma Model ◽  
Point Interaction ◽  
Low Energy ◽  
Linear Sigma Model ◽  
Pseudoscalar Mesons ◽  
Decay Widths ◽  
Symmetry Breaking Term ◽  
The Masses ◽  
Breaking Term

A procedure for implementation of the generating equations in the linear sigma model of low energy QCD is presented. For any explicit symmetry breaking term, this procedure computes the masses of scalar and pseudoscalar mesons as well as various three-point and four-point interaction vertices that are needed in calculation of different decay widths and scattering amplitudes.

CHIRAL SYMMETRY RESTORATION IN THE LINEAR SIGMA MODEL

1992 ◽  
Vol 03 (05) ◽  
pp. 993-1009 ◽  
Author(s):  
H. MEYER-ORTMANNS ◽  
H.-J. PIRNER ◽  
A. PATKÓS
Keyword(s):  
Chiral Symmetry ◽  
Sigma Model ◽  
Chiral Limit ◽  
Linear Sigma Model ◽  
Tree Level ◽  
Gradual Change ◽  
Chiral Symmetry Restoration ◽  
Meson Octet ◽  
First Order Transition ◽  
Experimental Values

We report on results about the mass sensitivity of chiral symmetry restoration in the linear sigma model. For masses of the pseudoscalar meson octet which are close to the experimental values, we observed only a gradual change in the order parameters, when the temperature was changed. To estimate the size of the first order transition region around the chiral limit, we have varied the mass input for the tree level parametrization in several ways. The point with realistic meson masses turned out to lie well inside the crossover region.

scholarly journals SYMMETRIES AND AMBIGUITIES IN THE LINEAR SIGMA MODEL WITH LIGHT QUARKS

2006 ◽  
Vol 21 (04) ◽  
pp. 339-347 ◽  
Author(s):  
E. W. DIAS ◽  
B. HILLER ◽  
A. L. MOTA ◽  
M. C. NEMES ◽  
M. SAMPAIO ◽  
...  
Keyword(s):  
Chiral Symmetry ◽  
Sigma Model ◽  
Decay Constant ◽  
Linear Sigma Model ◽  
Pion Decay ◽  
Radiative Corrections ◽  
Pion Decay Constant ◽  
Renormalization Procedure

We investigate the role of undetermined finite contributions generated by radiative corrections in an SU (2)× SU (2) linear sigma model with quarks. Although some of such terms can be absorbed in the renormalization procedure, one such contribution is left in the expression for the pion decay constant. This arbitrariness is eliminated by chiral symmetry.

NUCLEAR EQUATION OF STATE IN THE MODIFIED CHIRAL SIGMA MODEL

1994 ◽  
Vol 09 (39) ◽  
pp. 3641-3651
Author(s):  
PRADIP K. SAHU
Keyword(s):  
Sigma Model ◽  
Negative Energy ◽  
Saturation Density ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Projection Operators ◽  
Coupling Constant ◽  
Vector Coupling ◽  
Nuclear Equation Of State ◽  
Scalar Coupling Constant

We have developed a modified chiral sigma model by expressing the scalar and the vector vertices in terms of the positive- and negative-energy projection operators with two additional free parameters. The scalar and the vector coupling constants depend on the density of our model. We find that at densities higher than that of the saturation, the energy per particle decreases as the scalar coupling constant becomes stronger. In this model, the values of incompressibility and effective nucleon mass at the saturation density are sensitive to the strength of the scalar coupling constant. We find that the modified chiral sigma model can overcome the most of the shortcomings of the chiral sigma model and reproduce values of incompressibility, nucleon effective mass and coupling constants at the saturation density in the acceptable range.

scholarly journals Chiral Perturbation Theory vs. Linear Sigma Model in A Chiral Imbalance Medium

2019 ◽  
Author(s):  
Alexander Andrianov ◽  
Vladimir Andrianov ◽  
Domenec Espriu
Keyword(s):  
Perturbation Theory ◽  
Chiral Perturbation Theory ◽  
Sigma Model ◽  
Decay Constant ◽  
Charged Pion ◽  
Low Energy ◽  
Linear Sigma Model ◽  
Chiral Perturbation ◽  
Energy Constants ◽  
Parity Breaking

We compare Chiral Perturbation Theory (ChPT) and the Linear Sigma Model (LSM) as realizations of low energy QCD for light mesons in a chirally imbalanced medium. The relations between the low-energy constants of the Chiral Lagrangian and the corresponding constants of the Linear Sigma Model are established as well as the expressions for the decay constant of $\pi $-meson in the medium and for the mass of the $a_0$. In the large $N_c$ count taken from QCD the correspondence of ChPT and LSM is remarkably good and give a solid ground for search of chiral imbalance manifestation in pion physics. A possible experimental detection of chiral imbalance (and therefore a phase with Local Parity Breaking) is outlined in the charged pion decays inside the fireball.

scholarly journals Quark and glue spectroscopy of scalars and pseudoscalars in SU(3) flavor limit

2019 ◽  
Vol 34 (06n07) ◽  
pp. 1950034
Author(s):  
Amir H. Fariborz ◽  
Renata Jora ◽  
Maria Lyukova
Keyword(s):  
Numerical Simulation ◽  
Sigma Model ◽  
Linear Sigma Model ◽  
Pseudoscalar Mesons ◽  
Singlet States ◽  
Scalar Octet ◽  
Light Scalar ◽  
The Masses

Within the framework of the generalized linear sigma model with glueballs recently proposed,[Formula: see text] we study the schematic spectroscopy of scalar and pseudoscalar mesons in the SU(3) flavor limit and explore their quark and glue contents. In this framework, for both scalars and pseudoscalars, the two octet physical states are admixtures of quark–antiquark and four-quark components, and the three singlet states contain quark–antiquark, four-quark and glue components. We identify the two scalar octets with [Formula: see text] and [Formula: see text] and the two pseudoscalar octets with [Formula: see text] and [Formula: see text]. We show that, as expected, the light pseudoscalar octet is made dominantly of quark–antiquarks whereas the light scalar octet has a reversed substructure with a dominant four-quark component. The case of singlets is more complex due to surplus of states up to around 2 GeV. We consider all 35 permutations for identifying the three pseudoscalar singlets of our model with three of the seven experimental candidates. Our numerical simulation unambiguously identifies the lightest and the heaviest pseudoscalar singlets with [Formula: see text] and [Formula: see text], respectively, and favors the identification of the middle singlet with either [Formula: see text] or [Formula: see text] (or, to a lesser extent, with [Formula: see text]) and thereby allows a probe of their substructures. We then estimate the quark and glue components and find that the three pseudoscalar singlets (from lightest to heaviest) are mainly of quark–antiquark, four-quark and glue substructure, while the corresponding three scalar singlets (from lightest to heaviest) are of four-quark, quark–antiquark and glue contents. The masses of pure pseudoscalar and scalar glueballs are estimated around 2.0 and 1.6 GeV, respectively.

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