arXiv subjects

Weiqin Chao

Publications and source records attributed to Weiqin Chao.

8 recordsLinked to original sources

arXiv2002

Charge Neutrality Effects on 2-flavor Color Superconductivity

The effect of electric and color neutrality on 2-flavor color superconductivity has been investigated. It has been found that the effect of the charge neutrality on a 2-flavor quark system is very different from that on a 3-flavor system. The BCS diquark pair in 2-flavor color superconducting phase has been largely reduced by the large Fermi momentum of electron, the diquark condensate first increases with the increasing of quark's chemical potential $μ$,then decreases rapidly and finally disappears at about $μ=535MeV$, at which the thermodynamic potential equals to that in the neutral normal 2-flavor quark matter.

hep-ph↗

arXiv2002

Massive Quark Propagator in the Color-superconducting Phase

A more general expression for the quark propagator including both chiral and diquark condensates has been derived by using energy projectors. This makes it possible to study the phase transition from hadron phase to color superconductivity phase in the moderate baryon density region by using Feynman diagrammatic method or Green-function method.

hep-ph↗

arXiv2001

Color Superconductivity at Moderate Density

The effect of color breaking on colored quarks' chiral condensates has been investigated at zero temperature and moderate baryon density. It is found that the influence of the diquark condensate on different colored quarks is very small.

hep-ph↗

arXiv2001

The Mesonic Fluctuations and Corrections in the Chiral Symmetry Breaking Vacuum

The mesonic quantum fluctuations and their corrections on the chiral condensate and pion polarization function are investigated in the self-consistent scheme of SU(2) Nambu-Jona-Lasinio model by exactly calculating the next-to-leading order (NLO) Feynman diagrams in $1/N_c$ expansion. While the fluctuations and corrections depend strongly on the meson's three-momentum cut-off $Λ_M$, no chiral symmetry restoration is found since the cancellation between the NLO and the one-quark-loop diagram with quark mass deviated from the mean-field value.

hep-ph↗

arXiv2001

Meson Effects on Chiral Condensate at Finite Density

Meson corrections on chiral condensate up to next-to-leading order in $1/N_c$ expansion at finite density are investigated in NJL model with chiral symmetry explicitly breaking. Compared with the mean-field results, the chiral phase transition is still of first order, while the properties at the critical density of chiral phase transition are found to change significantly.

hep-ph↗

arXiv1999

S-wave $π- π$ Scattering Lengths in the SU(2) NJL Model Beyond Mean-field Approximation

The S-wave $π- π$ scattering lengths $a_0$ and $a_2$ are calculated to the lowest order of $1/N_c$ expansion in the general framework of SU(2) NJL model beyond mean-field approximation. It is shown that using the universal curve of $a_0$ and $a_2$ the four NJL parameters, i.e., the current quark mass $m_0$, the four fermion coupling constant $G$, the quark momentum cut-off $Λ_f$ and the meson momentum cut-off $Λ_b$, also the S-wave $π- π$ scattering lengths in NJL model can be uniquely determined.

hep-ph↗

arXiv1999

$π- π$ Scattering Lengths and Chiral Condensate in NJL Model

Within the general framework of SU(2) Nambu-Jona-Lasinio model beyond mean-field approximation, the S-wave $π- π$ scattering lengths $a_0^0$ and $a_0^2$ are calculated. The numerical results are in agreement with that analyzed from recent experiment $πN \to ππN$ data by using Chew-Low-Goebel technique, and the corresponding chiral condensate $<{\bar q}q>$ is around $-(250 {\rm MeV})^3$, which is close to the ones obtained from lattice and sum rules.

hep-ph↗

arXiv1999

Massive Meson Fluctuation in NJL Model

Based on the self-consistent scheme beyond mean-field approximation in the large $N_c$ expansion, including current quark mass explicitly, a general scheme of SU(2) NJL model is developed. To ensure the quark self-energy expanded in the proper order of $N_c$, an approximate internal meson propagator is deduced, which is in order of $O(1/N_c)$. In our scheme, adopting the method of external momentum expansion, all the Feynman diagrams are calculated in a unified way by only expanding the quark propagator. Our numerical results show, that different from the mean field approximation in which the explicitly chiral symmetry breaking is invisible, the effect of finite pion mass can be seen clearly when beyond mean-field approximation.

hep-ph↗