The QCD Vacuum and Chiral Symmetry

1990 ◽  
pp. 87-117 ◽  
Author(s):  
Jürg Gasser
Keyword(s):  
Chiral Symmetry ◽  
Qcd Vacuum

scholarly journals Domain wall network as QCD vacuum: confinement, chiral symmetry, hadronization

2017 ◽  
Vol 137 ◽  
pp. 03014
Author(s):  
Sergei N. Nedelko ◽  
Vladimir V. Voronin
Keyword(s):  
Domain Wall ◽  
Chiral Symmetry ◽  
Qcd Vacuum

CHIRAL SYMMETRY BREAKING IN A PHENOMENOLOGICAL DESCRIPTION OF THE QCD VACUUM

1992 ◽  
Vol 01 (01) ◽  
pp. 73-94 ◽  
Author(s):  
S. SCHRAMM ◽  
W. GREINER
Keyword(s):  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Phenomenological Description ◽  
Bcs Theory ◽  
Qcd Vacuum

Quark–antiquark condensation in the QCD groundstate is discussed in the framework of BCS theory. Adopting a phenomenological interaction between the quarks, the vacuum wavefunction is determined variationally. Taking these results, the properties of the vacuum and its excitations are determined. In addition the effect of instanton-type induced quark interactions is discussed.

scholarly journals ENTROPY IN QUANTUM CHROMODYNAMICS

2012 ◽  
Vol 27 (09) ◽  
pp. 1230011 ◽  
Author(s):  
JOHN M. CORNWALL
Keyword(s):  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Entanglement Entropy ◽  
Configurational Entropy ◽  
Zero Temperature ◽  
Massive Quark ◽  
Flux Tubes ◽  
Qcd Vacuum ◽  
Symmetry Breakdown

We review the role of zero-temperature entropy in several closely-related contexts in QCD. The first is entropy associated with disordered condensates, including [Formula: see text]. The second is effective vacuum entropy arising from QCD solitons such as center vortices, yielding confinement and chiral symmetry breaking. The third is entanglement entropy, which is entropy associated with a pure state, such as the QCD vacuum, when the state is partially unobserved and unknown. Typically, entanglement entropy of an unobserved three-volume scales not with the volume but with the area of its bounding surface. The fourth manifestation of entropy in QCD is the configurational entropy of light-particle world-lines and flux tubes; we argue that this entropy is critical for understanding how confinement produces chiral symmetry breakdown, as manifested by a dynamically-massive quark, a massless pion, and a [Formula: see text] condensate.

scholarly journals DOES ONE OBSERVE CHIRAL SYMMETRY RESTORATION IN BARYON SPECTRUM?

2002 ◽  
Vol 17 (10) ◽  
pp. 1327-1353 ◽  
Author(s):  
THOMAS D. COHEN ◽  
LEONID YA. GLOZMAN
Keyword(s):  
Chiral Symmetry ◽  
Experimental Studies ◽  
Spontaneous Breaking ◽  
Operator Product ◽  
Asymptotic Freedom ◽  
Chiral Symmetry Restoration ◽  
Baryon Spectrum ◽  
Qcd Vacuum ◽  
Doublet Structure ◽  
Recent Developments

It has recently been suggested that the parity doublet structure seen in the spectrum of highly excited baryons may be due to effective chiral symmetry restoration for these states. We review the recent developments in this field. We demonstrate with a simple quantum-mechanical example that it is a very natural property of quantum systems that a symmetry breaking effect which is important for the low-lying spectrum of the system, can become unimportant for the highly-lying states; the highly lying states reveal a multiplet structure of nearly degenerate states. Using the well-established concepts of quark–hadron duality, asymptotic freedom in QCD and validity of the operator product expansion in QCD, we show that the spectral densities obtained with the local currents that are connected to each other via chiral transformations, very high in the spectrum must coincide. Hence effects of spontaneous breaking of chiral symmetry in QCD vacuum that are crucially important for the low-lying spectra, become irrelevant for the highly-lying states. Then to the extent that identifiable hadronic resonances still exist in the continuum spectrum at high excitations, this implies that the highly excited hadrons must fall into multiplets associated with the representations of the chiral group. We demonstrate that this is indeed the case for meson spectra in the large Nc limit. All possible parity-chiral multiplets are classified for baryons and it is demonstrated that the existing data on highly excited N and Δ states at masses of 2 GeV and higher is consistent with approximate chiral symmetry restoration. However new experimental studies are needed to achieve any definitive conclusions.

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