Aspects of confinement from QCD correlation functions
Christian S. Fischer, Axel Maas, Jan M. Pawlowski
备注：
5 pages, 2 figures; invited talk presented by CF at the conference "Quark Confinement and the Hadron Spectrum VIII", Mainz, Germany, 1st-6th of September 2008
We discuss the properties of ghost and gluon propagators in Landau gauge Yang-Mills theory and their relation to the confinement problem. In general two types of infrared behavior of these functions are allowed from their functional equations: scaling and decoupling. Both solutions show positivity violations in the gluon propagator and lead to a confining Polyakov loop potential. However, only the scaling solution agrees with the Kugo-Ojima confinement scenario and the related formulation of a physical Hilbert space of Yang-Mills theory. Our numerical results for the gluon dressing function agree almost pointwise with the lattice results at all physical momenta.
Colormagnetic confinement as a natural component of the QCD confinement is explained and treated in the framework of the Field Correlator Method. For quarks and gluons in hadrons the effects of the colormagnetic confinement are discussed at zero temperature, where it contributes to the spectrum properties and can create its own bound states, while at nonzero temperature in the EoS of the quark gluon plasma the colormagnetic confinement plays a dominating role. Its properties in the QCD thermodynamics are discussed in detail.
We study confinement and chiral symmetry breaking phase transitions for QCD and supersymmetric QCD. The method is based on some justified assumption regarding the behavior of the Green function relevant for the potential between two charges or a gap equation. We determine the number of flavors at which the transitions to confinement and chiral symmetry breaking take place. We find that whereas for chiral symmetry breaking the results are in perfect agreement with those in the literature for confinement the situation is more complex.
The scalar confinement in QCD is shown to produce the nonzero quark condensate for any current quark mass. Mechanisms for the Chiral Symmetry breaking and for the nonzero quark condensates are revealed. For the light and strange flavors the condensates are essentially chiral (proportional to (string tension)$^{3/2}$). The expressions for the quark condensates are obtained as a sum over non-chiral meson states, and, using the operator product expansion, as an explicit expression that involves the confining string tension and the current quark mass. The numerical results are fairly close to the …
We provide an analytical derivation of the confinement deconfinement phase transition to QCD in the pure gluon sector at finite temperature within the framework of S U(3) dual QCD formulation. The mechanism of color confinement has been explained by adopting magnetic symmetry to extract magnetic monopoles in a gauge invariant way and produce magnetic condensation of S U(3) dual QCD vacuum which guarantees the dual Meissner effect. The deconfinement phase transition has been described by constructing the effective potential at finite temperature in the imaginary time formalism. The magnetic mon…
If the strong coupling is promoted to a dynamical field-dependent quantity, it is possible that the strong force looked very different in the early Universe. We consider a scenario in which the dynamics is such that QCD confines at high temperatures with a large dynamical scale, relaxing back to ~1 GeV before big bang nucleosynthesis. We discuss the cosmological implications and explore potential applications, including fleshing out a new mechanism for baryogenesis which opens up if QCD confines before the electroweak phase transition of the Standard Model.
We provide a study of quantum chromodynamics with the technique of Dyson-Schwinger equations in differential form. In this way, we are able to approach the non-perturbative limit and recover, with some approximations, the 't Hooft limit of the theory. Quark mass in the propagator term goes off-shell at low-energies signaling confinement. A condition for such occurrence in the theory is provided.
The mechanism of color confinement has been studied in the framework of SU (3) color gauge theory in terms of abelian fields and monopoles extracted by adopting magnetic symmetry. The existence of the mechanism of color confinement corresponds to the dual Meissner effect caused by monopoles. The two length scales, i.e. the penetration depth and coherence length are defined to demonstrate the scaling nature of the QCD vacuum and their ratio defines the Ginzburg-Landau parameter indicating the border of type I and type II dual superconductor. The existence of these two length scales describes th…
Standard lore states that there is tension between the need to accommodate the relic density of a weakly interacting massive particle and direct searches for dark matter. However, the estimation of the relic density rests on an extrapolation of the cosmology of the early Universe to the time of freeze out, untethered by observations. We explore a nonstandard cosmology in which the strong coupling constant evolves in the early Universe, triggering an early period of QCD confinement at the time of freeze out. We find that depending on the nature of the interactions between the dark matter and th…
We study in this Letter the origin of the confinement in QCD by analyzing the colour charge of physics states. We derive the colour charge operator in QCD and compare it with the electromagnetic charge operator in QED. It shows that the two charges have very similar structure, but the dynamical properties of the gauge fields are different. The difference between the behaviours of the gauge boson propagator at zero momentum for QCD and that for QED guarantees that there occurs colour confinement in QCD but there is no confinement in QED. We give then a universal relation between the confinement…
An approach to QCD vacuum as a medium describable in terms of statistical ensemble of almost everywhere homogeneous Abelian (anti-)self-dual gluon fields is briefly reviewed. These fields play the role of the confining medium for color charged fields as well as underline the mechanism of realization of chiral $SU_{\rm L}(N_f)\times SU_{\rm R}(N_f)$ and $U_A(1)$ symmetries. Hadronization formalism based on this ensemble leads to manifestly defined quantum effective meson action. Strong, electromagnetic and weak interactions of mesons are represented in the action in terms of nonlocal $n$-point …
Three current models of QCD in (1+1) dimensions are examined and extended in light-front coordinates. A pion of high momentum is found to have an infinite extent along its direction of motion.
We study confinement-deconfinement phase transition in a holographic soft-wall QCD model. By solving the Einstein-Maxwell-scalar system analytically, we obtain the phase structure of the black hole backgrounds. We then impose probe open strings in such background to investigate the confinement-deconfinement phase transition from different open string configurations under various temperatures and chemical potentials. Furthermore, we study the Wilson loop by calculating the minimal surface of the probing open string world-sheet and obtain the Cornell potential in confinement phase analytically.
Momentum sum rule in QCD is widely used at high energy colliders. Although the exact form of the confinement potential energy is not known but the confinement potential energy at large distance $r$ can not rise slower than ${\rm ln}(r)$. In this paper we find that if the confinement potential energy at large distance $r$ rises linearly with $r$ (or faster) then the momentum sum rule in QCD is violated at the high energy colliders if we consider the hadron size as infinite. For finite size hadron we find that the momentum sum rule in QCD is violated at the high energy colliders for any form of …
