Three regimes of QCD

2021 ◽  
pp. 2044031
Author(s):  
L. Ya. Glozman
Keyword(s):  
Dirac Operator ◽  
Quark Gluon Plasma ◽  
Degrees Of Freedom ◽  
Magnetic Interaction ◽  
Gluon Plasma ◽  
Magnetic Interactions ◽  
Hadron Spectrum ◽  
Zero Modes ◽  
Electric Interaction ◽  
Hadron Gas

While the QCD Lagrangian as the whole is only chirally symmetric, its electric part has larger chiral-spin [Formula: see text] and [Formula: see text] symmetries. This allows separation of the electric and magnetic interactions in a given reference frame. Artificial truncation of the near-zero modes of the Dirac operator results in the emergence of the [Formula: see text] and [Formula: see text] symmetries in hadron spectrum. This implies that while the confining electric interaction is distributed among all modes of the Dirac operator, the magnetic interaction is located at least predominantly in the near-zero modes. Given this observation one could anticipate that above the pseudocritical temperature, where the near-zero modes of the Dirac operator are suppressed, QCD is [Formula: see text] and [Formula: see text] symmetric, which means absence of deconfinement in this regime. Solution of the [Formula: see text] QCD on the lattice with a chirally symmetric Dirac operator reveals that indeed in the interval [Formula: see text] QCD is approximately [Formula: see text] and [Formula: see text] symmetric which implies that degrees of freedom are chirally symmetric quarks bound by the chromoelectric field into color-singlet objects without the chromomagnetic effects. This regime is referred to as a Stringy Fluid. At larger temperatures this emergent symmetry smoothly disappears and QCD approaches the Quark–Gluon Plasma regime with quasifree quarks. The Hadron Gas, the Stringy Fluid and the Quark–Gluon Plasma differ by symmetries, degrees of freedom and properties.

scholarly journals Chiralspin Symmetry and Its Implications for QCD

Universe ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 38 ◽  
Author(s):  
Leonid Glozman
Keyword(s):  
Dirac Operator ◽  
Invariant Theory ◽  
Magnetic Interaction ◽  
Kinetic Term ◽  
Dirac Fermions ◽  
Gauge Invariant ◽  
Zero Modes ◽  
Left Handed ◽  
Electric Interaction ◽  
The Right

In a local gauge-invariant theory with massless Dirac fermions, a symmetry of the Lorentz-invariant fermion charge is larger than a symmetry of the Lagrangian as a whole. While the Dirac Lagrangian exhibits only a chiral symmetry, the fermion charge operator is invariant under a larger symmetry group, S U ( 2 N F ) , that includes chiral transformations as well as S U ( 2 ) C S chiralspin transformations that mix the right- and left-handed components of fermions. Consequently, a symmetry of the electric interaction, which is driven by the charge density, is larger than a symmetry of the magnetic interaction and of the kinetic term. This allows separating in some situations electric and magnetic contributions. In particular, in QCD, the chromo-magnetic interaction contributes only to the near-zero modes of the Dirac operator, while confining chromo-electric interaction contributes to all modes. At high temperatures, above the chiral restoration crossover, QCD exhibits approximate S U ( 2 ) C S and S U ( 2 N F ) symmetries that are incompatible with free deconfined quarks. Consequently, elementary objects in QCD in this regime are quarks with a definite chirality bound by the chromo-electric field, without the chromo-magnetic effects. In this regime, QCD can be described as a stringy fluid.

scholarly journals SU(2NF) symmetry of confinement in QCD and its observation at high temperature.

2018 ◽  
Vol 182 ◽  
pp. 02046 ◽  
Author(s):  
L.Ya. Glozman
Keyword(s):  
High Temperature ◽  
Dirac Operator ◽  
Magnetic Interaction ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Zero Modes ◽  
Left Handed ◽  
Electric Interaction ◽  
The Right ◽  
Increasing Temperature

In this talk we first overview lattice results that have led to the observation of new SU(2)CS and SU(2NF) symmetries upon artificial truncation of the near-zero modes of the Dirac operator at zero temperatute and at high temperature without any truncation. These symmetries are larger than the chiral symmetry of the QCD Lagrangian and contain chiral symmetries SU(NF)L x SU(NF)R and U(1)A as subgroups. In addition to the standard chiral transformations the SU(2)CS and SU(2NF) transformations mix the right- and left-handed components of the quark fields. It is a symmetry of the confining chromo-electric interaction while the chromo-magnetic interaction manifestly breaks it. Emergence of these symmetries upon truncation of the near-zero modes of the Dirac operator at T=0 means that all effects of the chromo-magnetic interaction are located exclusively in the near-zero modes, while confining chromo-electric interaction is distributed among all modes. Appearance of these symmetries at high T, where the temperature suppresses the near-zero modes, has radical implications because these symmetries are incompatible with the asymptotically free deconfined quarks at increasing temperature. The elementary objects in the high-temperature phase of QCD should be quarks bound by the pure chromo-electric field that is not accompanied by the chromo-magnetic effects.

scholarly journals Quark Cluster Expansion Model for Interpreting Finite-T Lattice QCD Thermodynamics

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 514
Author(s):  
David Blaschke ◽  
Kirill A. Devyatyarov ◽  
Olaf Kaczmarek
Keyword(s):  
Lattice Qcd ◽  
Cluster Expansion ◽  
Quark Gluon Plasma ◽  
Degrees Of Freedom ◽  
Gluon Plasma ◽  
Polyakov Loop ◽  
Unified Approach ◽  
Narrow Temperature Interval ◽  
Levinson Theorem ◽  
Expansion Model

In this work, we present a unified approach to the thermodynamics of hadron–quark–gluon matter at finite temperatures on the basis of a quark cluster expansion in the form of a generalized Beth–Uhlenbeck approach with a generic ansatz for the hadronic phase shifts that fulfills the Levinson theorem. The change in the composition of the system from a hadron resonance gas to a quark–gluon plasma takes place in the narrow temperature interval of 150–190 MeV, where the Mott dissociation of hadrons is triggered by the dropping quark mass as a result of the restoration of chiral symmetry. The deconfinement of quark and gluon degrees of freedom is regulated by the Polyakov loop variable that signals the breaking of the Z(3) center symmetry of the color SU(3) group of QCD. We suggest a Polyakov-loop quark–gluon plasma model with O(αs) virial correction and solve the stationarity condition of the thermodynamic potential (gap equation) for the Polyakov loop. The resulting pressure is in excellent agreement with lattice QCD simulations up to high temperatures.

scholarly journals Holographic Multiquarks in the Quark-Gluon Plasma: A Review

2011 ◽  
Vol 2011 ◽  
pp. 1-40 ◽  
Author(s):  
Piyabut Burikham ◽  
Ekapong Hirunsirisawat
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Magnetic Properties ◽  
Quark Gluon Plasma ◽  
Bound States ◽  
Degrees Of Freedom ◽  
Gluon Plasma ◽  
Screening Length ◽  
Holographic Approach ◽  
Multiquark States

We review the holographic multiquark states in the deconfined quark-gluon plasma. Nuclear matter can become deconfined by extremely high temperature and/or density. In the deconfined nuclear medium, bound states with colour degrees of freedom are allowed to exist. Using holographic approach, the binding energy and the screening length of the multiquarks can be calculated. Using the deconfined Sakai-Sugimoto model, the phase diagram of the multiquark phase, the vacuum phase, and the chiral-symmetric quark-gluon plasma can be obtained. Then we review the magnetic properties of the multiquarks and their phase diagrams. The multiquark phase is compared with the pure pion gradient, the magnetized vacuum, and the chiral-symmetric quark-gluon plasma phases. For moderate temperature and sufficiently large density at a fixed magnetic field, the mixed phase of multiquark and pion gradient is the most energetically preferred phase.

Quark-gluon plasma versus hadron gas. What one can learn from hadron abundances

1988 ◽  
Vol 37 (4) ◽  
pp. 1452-1462 ◽  
Author(s):  
Kang S. Lee ◽  
M. J. Rhoades-Brown ◽  
Ulrich Heinz
Keyword(s):  
Quark Gluon Plasma ◽  
Gluon Plasma ◽  
Hadron Gas

scholarly journals Effective degrees of freedom of the quark–gluon plasma

2007 ◽  
Vol 644 (5-6) ◽  
pp. 336-339 ◽  
Author(s):  
P. Castorina ◽  
M. Mannarelli
Keyword(s):  
Quark Gluon Plasma ◽  
Degrees Of Freedom ◽  
Gluon Plasma

scholarly journals Degrees of Freedom of the Quark Gluon Plasma, Tested by Heavy Mesons

2016 ◽  
pp. 151-165 ◽  
Author(s):  
H. Berrehrah ◽  
M. Nahrgang ◽  
T. Song ◽  
V. Ozvenchuck ◽  
P. B. Gossiaux ◽  
...  
Keyword(s):  
Quark Gluon Plasma ◽  
Degrees Of Freedom ◽  
Gluon Plasma ◽  
Heavy Mesons

EFFECTIVE MESONIC AND BARYONIC DEGREES OF FREEDOM IN NEUTRON STARS

2004 ◽  
Vol 13 (07) ◽  
pp. 1365-1373 ◽  
Author(s):  
MANFRED DILLIG ◽  
MATHIAS SCHOTT ◽  
EDUARDO F. LÜTZ ◽  
ALEXANDRE MESQUITA ◽  
CÉSAR A. Z. VASCONCELLOS
Keyword(s):  
Neutron Stars ◽  
Quark Gluon Plasma ◽  
Degrees Of Freedom ◽  
Gluon Plasma ◽  
Hadronic Matter

We present a sketchy survey on the role of effective mesonic and baryonic degrees of freedom in dense hadronic matter and briefly mention still very crude attempts to include constituent quarks degrees of freedom for a transition to a quark gluon plasma.

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