Si-xue Qin

Interaction model for the gap equation

We explain a form for the rainbow-ladder kernel whose momentum-dependence is consonant with modern DSE- and lattice-QCD results, and assess its capability as a tool in hadron physics. In every respect tested, this form produces results for observables that are at least equal to the best otherwise obtained in a comparable approach. Moreover, it enables the natural extraction of a monotonic running-coupling and -gluon-mass.

Investigation of rainbow-ladder truncation for excited and exotic mesons

Si-xue Qin, Lei Chang, Yu-xin Liu, 3 Craig D. Roberts, 2, 4 and David J. Wilson Department of Physics, Center for High Energy Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000, China Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616-3793, USA

Phase Diagram and Critical End Point for Strongly Interacting Quarks

We introduce a method based on chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential-temperature plane for strongly interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical end point at (μ(E),T(E))∼(1.0,0.9)T(c), where T(c) is the critical temperature for chiral-symmetry restoration at μ=0, and find that a domain of phase coexistence opens at the critical end point whose area increases as a confinement length scale grows.

Practical corollaries of transverse Ward-Green-Takahashi identities

The gauge principle is fundamental in formulating the Standard Model. Fermion–gauge-boson couplings are the inescapable consequence and the primary determining factor for observable phenomena. Vertices describing such couplings are simple in perturbation theory and yet the existence of strong-interaction bound-states guarantees that many phenomena within the Model are nonperturbative. It is therefore crucial to understand how dynamics dresses the vertices and thereby fundamentally alters the appearance of fermion–gauge-boson interactions. We consider the coupling of a dressed-fermion to an Abelian gauge boson, and describe a unified treatment and solution of the familiar longitudinal Ward-Green-Takahashi identity and its less well known transverse counterparts. Novel consequences for the dressed-fermion–gauge-boson vertex are exposed.

Symmetry preserving truncations of the gap and Bethe-Salpeter equations

Ward-Green-Takahashi (WGT) identities play a crucial role in hadron physics, e.g. imposing stringent relationships between the kernels of the one- and two-body problems, which must be preserved in any veracious treatment of mesons as bound-states. In this connection, one may view the dressed gluon-quark vertex,

Existence and stability of multiple solutions to the gap equation

\Gamma_\mu^a

Zero mode in a strongly coupled quark gluon plasma

, as fundamental. We use a novel representation of

Phase diagram and thermal properties of strong-interaction matter

\Gamma_\mu^a

Quark spectral density and a strongly-coupled QGP

, in terms of the gluon-quark scattering matrix, to develop a method capable of elucidating the unique quark-antiquark Bethe-Salpeter kernel,

Quark spectral density and a strongly-coupled quark-gluon plasma.

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