scholarly journals QCD phase diagram in a constant magnetic background

2021 ◽  
Vol 57 (6) ◽  
Author(s):  
Jens O. Andersen
Keyword(s):  
Magnetic Field ◽  
Pion Mass ◽  
Quark Condensate ◽  
Low Energy ◽  
Magnetic Catalysis ◽  
Qcd Phase Diagram ◽  
Straightforward Application ◽  
Energy Models ◽  
Njl Model ◽  
Correct Determination

AbstractMagnetic catalysis is the enhancement of a condensate due to the presence of an external magnetic field. Magnetic catalysis at $$T=0$$ T = 0 is a robust phenomenon in low-energy theories and models of QCD as well as in lattice simulations. We review the underlying physics of magnetic catalysis from both perspectives. The quark-meson model is used as a specific example of a model that exhibits magnetic catalysis. Regularization and renormalization are discussed and we pay particular attention to a consistent and correct determination of the parameters of the Lagrangian using the on-shell renormalization scheme. A straightforward application of the quark-meson model and the NJL model leads to the prediction that the chiral transition temperature $$T_{\chi }$$ T χ is increasing as a function of the magnetic field B. This is in disagreement with lattice results, which show that $$T_{\chi }$$ T χ is a decreasing function of B, independent of the pion mass. The behavior can be understood in terms of the so-called valence and sea contributions to the quark condensate and the competition between them. We critically examine these ideas as well recent attempts to improve low-energy models using lattice input.

NJL model with the modified quark-dependent coupling strength G

2017 ◽  
Vol 32 (20) ◽  
pp. 1750107 ◽  
Author(s):  
Zhou-You Fan ◽  
Wen-Kai Fan ◽  
Qing-Wu Wang ◽  
Hong-Shi Zong
Keyword(s):  
Coupling Strength ◽  
Finite Temperature ◽  
Chemical Potential ◽  
Chiral Limit ◽  
Pion Mass ◽  
Quark Condensate ◽  
Qcd Phase Diagram ◽  
Njl Model ◽  
Lattice Quantum ◽  
Current Quark

In this paper, the coupling strength G of the Nambu–Jona-Lasinio (NJL) model is modified by incorporating quark’s feedback into the gluon propagator. The modified two-flavor NJL model with the quark-dependent coupling strength is explored. The quark condensate in this framework has a conspicuous agreement with the lattice quantum chromodynamics (QCD) results at finite temperature. Then, it is compared with the original NJL model in both zero (chiral limit) and nonzero current quark mass. The QCD phase diagram and susceptibilities are investigated in the temperature–chemical potential [Formula: see text] plane. Therefore, the pseudo-critical temperature [Formula: see text] and the critical end point (CEP) are worked out and compared with original NJL model or lattice QCD results. In addition, the pion mass and decay constant are studied at finite temperature.

Thermodynamic properties of light mesons and phase transition in an extended SU(2) NJL model

2019 ◽  
Vol 34 (13) ◽  
pp. 1950070
Author(s):  
J. R. Morones Ibarra ◽  
A. J. Garza Aguirre ◽  
Francisco V. Flores-Baez
Keyword(s):  
Chemical Potential ◽  
Pion Mass ◽  
Quark Condensate ◽  
The Other ◽  
Chiral Symmetry Restoration ◽  
Chiral Phase ◽  
Potential Dependence ◽  
Njl Model ◽  
The Masses ◽  
Sigma Meson

In this work, we study the temperature and chemical potential dependence of the masses of sigma and pion mesons as well as the quark condensate by using a SU(2) flavor version of the Nambu–Jona–Lassino model, introducing a prescription that mimics confinement. We have found that as the temperature increases, the mass of sigma shifts down, while the pion mass remains almost constant. On the other hand, the quark condensate decreases as the temperature and chemical potential increases. We have also analyzed the temperature and chemical potential dependence of the spectral function of the sigma meson, from which we observe at low values of T and [Formula: see text] an absence of a peak. Furthermore, as the Mott temperature is reached, its value increases abruptly and a distinct peak emerges, which is related with the dissociation of the sigma. For the case of [Formula: see text], the Mott dissociation is exhibited about the temperature of 189 MeV. We have also obtained the chiral phase diagram and the meson dissociation for different values of [Formula: see text]. From these results, we can state a relation between chiral symmetry restoration and Mott dissociation.

scholarly journals QCD phase diagram with a background magnetic field in an improved soft-wall AdS/QCD model

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Zhen Fang ◽  
Ying-Ying Li ◽  
Yue-Liang Wu
Keyword(s):  
Magnetic Field ◽  
Axial Vector ◽  
Vector Mesons ◽  
Magnetic Catalysis ◽  
Qcd Phase Diagram ◽  
Chiral Transition ◽  
Background Magnetic Field ◽  
Soft Wall Model ◽  
Soft Wall ◽  
Melting Properties

AbstractWe studied the magnetic effects on the chiral transition and the melting properties of vector and axial-vector mesons in the improved soft-wall AdS/QCD model under a charged magnetic background, which is solved perturbatively from an Einstein–Maxwell system with a negative cosmological constant. The phase diagrams for both chiral transition and meson melting have been obtained. We show that the inverse magnetic catalysis emerged naturally in the improved soft-wall model. We also find that the magnetic field can induce meson melting, at least for the vector and axial-vector mesons, in our holographic setup.

DYNAMICAL GAPS AND QUANTUM HALL EFFECT IN GRAPHENE

2009 ◽  
Vol 23 (07) ◽  
pp. 891-902
Author(s):  
E. V. GORBAR ◽  
V. P. GUSYNIN ◽  
V. A. MIRANSKY
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Ground State ◽  
Quantum Hall ◽  
Low Energy ◽  
Strong Magnetic Fields ◽  
Gap Equation ◽  
Magnetic Catalysis

We analyze the gap equation for Dirac quasiparticles in graphene in a magnetic field using a low-energy effective model with a contact interaction. It is found that the order parameters connected with the quantum Hall (QH) ferromagnetism and the magnetic catalysis scenarios necessarily coexist. The ground-state solutions of the gap equation describe all the recently discovered novel QH plateaus in graphene in strong magnetic fields.

scholarly journals To grow or not to grow: Thermomagnetic behavior of the strong coupling

2019 ◽  
Vol 206 ◽  
pp. 02001
Author(s):  
Alejandro Ayala ◽  
C. A. Dominguez ◽  
Saul Hernandez-Ortiz ◽  
L. A. Hernandez ◽  
M. Loewe ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Transition Temperature ◽  
Strong Coupling ◽  
Magnetic Field Dependence ◽  
Magnetic Field Intensity ◽  
Quark Condensate ◽  
Temperature Decrease ◽  
Magnetic Catalysis ◽  
The Magnetic Field

The properties of strongly interacting matter at finite temperature in a magnetized medium have received a great deal of attention in recent years, mainly due to the so called Inverse Magnetic Catalysis phenomenon whereby the pseudo critical quiral phase transition temperature and the quark condensate above this transition temperature decrease as a function of the magnetic field intensity. In this work we argue that this phenomenon is linked to the properties of the strong coupling when its temperature and magnetic field dependence are considered.

CHIRAL SYMMETRY BREAKING AND THE GLUON CONDENSATE

1993 ◽  
Vol 08 (04) ◽  
pp. 335-339
Author(s):  
M. FABER ◽  
A.N. IVANOV ◽  
M. NAGY ◽  
N.I. TROITSKAYA
Keyword(s):  
Magnetic Field ◽  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Sum Rules ◽  
Chiral Symmetry Breaking ◽  
Gluon Condensate ◽  
Quark Condensate ◽  
Low Energy ◽  
Qcd Sum Rules ◽  
Energy Approximation

For the low-energy approximation of QCD, the extended Nambu-Jona-Lasinio model has been used. Quarks interact with an external homogeneous color-magnetic field, simulating the contribution of the gluon condensate. The value of the gluon condensate, needed to reach the correct value of the quark condensate, is determined and agrees well with the value obtained from QCD sum rules.

scholarly journals Chiral magnetic properties of QCD phase-diagram

2021 ◽  
Vol 57 (6) ◽  
Author(s):  
Abdel Nasser Tawfik ◽  
Abdel Magied Diab
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Magnetic Susceptibility ◽  
Degrees Of Freedom ◽  
Linear Sigma Model ◽  
Critical Temperatures ◽  
Magnetic Catalysis ◽  
Qcd Phase Diagram ◽  
Hadron Phase ◽  
Chemical Potentials

AbstractThe QCD phase-diagram is studied, at finite magnetic field. Our calculations are based on the QCD effective model, the SU(3) Polyakov linear-sigma model (PLSM), in which the chiral symmetry is integrated in the hadron phase and in the parton phase, the up-, down- and strange-quark degrees of freedom are incorporated besides the inclusion of Polyakov loop potentials in the pure gauge limit, which are motivated by various underlying QCD symmetries. The Landau quantization and the magnetic catalysis are implemented. The response of the QCD matter to an external magnetic field such as magnetization, magnetic susceptibility and permeability has been estimated. We conclude that the parton phase has higher values of magnetization, magnetic susceptibility, and permeability relative to the hadron phase. Depending on the contributions to the Landau levels, we conclude that the chiral magnetic field enhances the chiral quark condensates and hence the chiral QCD phase-diagram, i.e. the hadron-parton phase-transition likely takes place, at lower critical temperatures and chemical potentials.

scholarly journals Landau levels in QCD in an external magnetic field

2018 ◽  
Vol 175 ◽  
pp. 07014 ◽  
Author(s):  
Falk Bruckmann ◽  
Gergely Endrődi ◽  
Matteo Giordano ◽  
Sándor D. Katz ◽  
Tamás G. Kovács ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Landau Level ◽  
Low Energy ◽  
Landau Levels ◽  
Dimensional Case ◽  
Strong Interactions ◽  
Two Dimensional ◽  
Energy Models ◽  
Lowest Landau Level

We will discuss the issue of Landau levels of quarks in lattice QCD in an external magnetic field. We will show that in the two-dimensional case the lowest Landau level can be identified unambiguously even if the strong interactions are turned on. Starting from this observation, we will then show how one can define a “plowest Landau level” in the four-dimensional case, and discuss how much of the observed effects of a magnetic field can be explained in terms of it. Our results can be used to test the validity of low-energy models of QCD that make use of the lowest-Landau-level approximation.

scholarly journals Exploring the BEC-BCS Crossover in a Cold and Magnetized 2-Color QCD

2017 ◽  
Vol 45 ◽  
pp. 1760066 ◽  
Author(s):  
Dyana C. Duarte ◽  
Pablo G. Allen ◽  
Ricardo L. S. Farias ◽  
Pedro H. A. Manso ◽  
Norberto N. Scoccola
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Regularization Scheme ◽  
Magnetic Catalysis ◽  
Chemical Potentials ◽  
Njl Model

We study the BEC-BCS crossover in the presence of an external magnetic field for a two color NJL model with diquark interactions, giving special attention to the regularization scheme. We found a inverse magnetic catalysis on the critical chemical potentials, both for BEC phase transition and the BEC-BCS crossover for small values of magnetic fields, and a magnetic catalysis for large [Formula: see text].

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