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Hong-Shi Zong

Publications and source records attributed to Hong-Shi Zong.

At least 109 records · Page 6Linked to original sources

Pauli equation for a charged spin particle on a curved surface in an electric and magnetic field

We derive the Pauli equation for a charged spin particle confined to move on a spatially curved surface $\mathcal{S}$ in an electromagnetic field. Using the thin-layer quantization scheme to constrain the particle on $\mathcal{S}$, and in the transformed spinor representations, we obtain the well-known geometric potential $V_g$ and the presence of $e^{-iφ}$, which can generate additive spin connection geometric potentials by the curvilinear coordinate derivatives, and we find that the two fundamental evidences in the literature [Giulio Ferrari and Giampaolo Cuoghi, Phys. Rev. Lett. 100, 230403 (2008).] are still valid in the present system without source current perpendicular to $\mathcal{S}$. Finally, we apply the surface Pauli equation to spherical, cylindrical, and toroidal surfaces, in which we obtain expectantly the geometric potentials and new spin connection geometric potentials, and find that only the normal Pauli matrix appears in these equations.

quant-ph↗

Influence of gauge boson mass on the staggered spin susceptibility

Based on the study of the linear response of the fermion propagator in the presence of an external scalar field, we calculate the staggered spin susceptibility in the low energy limit in the framework of the Dyson-Schwinger approach. We analyze the effect of a finite gauge boson mass on the staggered spin susceptibility in both Nambu phase and Wigner phase. It is found that the gauge boson mass suppresses the staggered spin susceptibility in Wigner phase. In addition, we try to give an explanation for why the antiferromagnetic spin correlation increases when the doping is lowered.

hep-ph↗

Locate QCD Critical End Point in a Continuum Model Study

With a modified chemical potential dependent effective model for the gluon propagator, we try to locate the critical end point (CEP) of strongly interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond the chiral limit, we find that Nambu solution and Wigner solution could coexist in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we show that these two phases are connected by a first order phase transition. We then locate CEP as the end point of the first order phase transition line. Meanwhile, based on CJT effective action, we give a direct calculation for the chiral susceptibility and thereby study the crossover.

hep-ph↗

Flavour symmetry breaking in the kaon parton distribution amplitude

We compute the kaon's valence-quark (twist-two parton) distribution amplitude (PDA) by projecting its Poincare'-covariant Bethe-Salpeter wave-function onto the light-front. At a scale ζ=2GeV, the PDA is a broad, concave and asymmetric function, whose peak is shifted 12-16% away from its position in QCD's conformal limit. These features are a clear expression of SU(3)-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state's momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on the difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD's conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, $F_K/F_π=1.23$ at spacelike-$Q^2=17\,{\rm GeV}^2$, which compares satisfactorily with the value of $0.92(5)$ inferred in $e^+ e^-$ annihilation at $s=17\,{\rm GeV}^2$.

nucl-th↗

A model study of the chiral phase diagram of QCD

In this paper we study the chiral phase transition of QCD at finite temperature and density by using the rank-2 confining separable gluon propagator model in the framework of Dyson-Schwinger Equations. The critical end point is located at (T_CEP, μ_CEP) = (69 MeV, 270.3 MeV). It is also found that the first order phase transition might not end at one point, but experiences a two-phase coexisting meta-stable state. A comparison with the results in the previous literature is given.

hep-ph↗

Constraints on the ultracompact minihalos using neutrino signals from the gravitino dark matter decay

Ultracompact dark matter minihalos (UCMHs) would be formed during the earlier universe if there were large density perturbations. If the dark matter can decay into the standard model particles, such as neutrinos, these objects would become the potential astrophysical sources and could be detected by the related instruments, such as IceCube. In this paper, we investigate the neutrino signals from the nearby UCMHs due to the gravitino dark matter decay and compare these signals with the background neutrino flux which is mainly from the atmosphere to get the constraints on the abundance of UCMHs.

astro-ph.CO↗

A thermodynamically consistent quasi-particle model without density-dependent infinity of the vacuum zero point energy

In this paper, we generalize the improved quasi-particle model proposed in J. Cao et al., [ Phys. Lett. B {\bf711}, 65 (2012)] from finite temperature and zero chemical potential to the case of finite chemical potential and zero temperature, and calculate the equation of state (EOS) for (2+1) flavor Quantum Chromodynamics (QCD) at zero temperature and high density. We first calculate the partition function at finite temperature and chemical potential, then go to the limit $T=0$ and obtain the equation of state (EOS) for cold and dense QCD, which is important for the study of neutron stars. Furthermore, we use this EOS to calculate the quark-number density, the energy density, the quark-number susceptibility and the speed of sound at zero temperature and finite chemical potential and compare our results with the corresponding ones in the existing literature.

hep-ph↗

The Dirac Conjecture and the Non-uniqueness of Lagrangian

By adding the total time derivatives of all the constraints to the Lagrangian step by step, we achieve the further work of the Dirac conjecture left by Dirac. Hitherto, the Dirac conjecture is proved completely. It is worth noticing that the addition of the total time derivatives to the Lagrangian can turn up some constraints hiding in the original Lagrangian. For a constrained system, the extended Hamiltonian $H_E$ considers more constraints, and shows symmetries more obviously than the total Hamiltonian $H_T$. In the Lagrangian formalism, we reconsider the Cawley counterexample, and offer an example in which in accordance with its original Lagrangian its extended Hamiltonian is better than its total Hamiltonian.

hep-th↗

Calculation of the staggered spin correlation in the framework of the Dyson-Schwinger approach

Based on the linear response of the fermion propagator with respect to an external field, we first derive a model-independent expression for the staggered spin susceptibility in which the influence of the full pseudoscalar vertex function is included. This expression for the staggered spin susceptibility is quite different from that given in the previous literature. The numerical values of the staggered spin susceptibility are calculated within the framework of the Dyson-Schwinger approach. Our numerical result shows that the nonperturbative dressing effects on the fermion propagator is very important when one studies the staggered spin susceptibility which corresponding to antiferromagnetic correlation in both Nambu phase and Winger phase.

cond-mat.str-el↗

Possible interpretation of the $Z_b$(10610) and $Z_b$(10650) in a chiral quark model

Motivated by the two charged bottomonium-like resonances $Z_b$(10610) and $Z_b$(10650) newly observed by the Belle collaboration, the possible molecular states composed of a pair of heavy mesons, $B\bar{B}, B\bar{B}^*, B^*\bar{B}^*, B_s\bar{B}$, etc (in S-wave), are investigated in the framework of chiral quark models by the Gaussian expansion method. The bound states $B\bar{B}^*$ and $B^*\bar{B}^*$ with quantum numbers $I(J^{PC})=1(1^{+-})$, which are good candidates for the $Z_b(10610)$ and $Z_b(10650)$ respectively, are obtained. Other three bound states $B\bar{B}^*$ with $I(J^{PC})=0(1^{++})$, $B^*\bar{B}^*$ with $I(J^{PC})=1(0^{++}), 0(2^{++})$ are predicted. These states may be observed in open-bottom or hidden-bottom decay channel of highly excited $Υ$. When extending directly the quark model to the hidden color channel of the multi-quark system, more deeply bound states are found. Future experimental search of those states will cast doubt on the validity of applying the chiral constituent quark model to the hidden color channel directly.

hep-ph↗

New application of decomposition of U(1) gauge potential:Aharonov-Bohm effect and Anderson-Higgs mechanism

In this paper we study the Aharonov-Bohm (A-B) effect and Anderson-Higgs mechanism in Ginzburg-Landau model of superconductors from the perspective of the decomposition of U(1) gauge potential. By the Helmholtz theorem, we derive exactly the expression of the transverse gauge potential $\vec{A}_\perp$ in A-B experiment, which is gauge-invariant and physical. For the case of a bulk superconductor, we find that the gradient of the total phase field $θ$ provides the longitudinal component ${\vec A}_{\parallel}$, which reflects the Anderson-Higgs mechanism. For the case of a superconductor ring, the gradient of the longitudinal phase field $θ_1$ provides the longitudinal component ${\vec A}_{\parallel}$, while the transverse phase field $θ_2$ produces new physical effects such as the flux quantization inside a superconducting ring.

cond-mat.supr-con↗

Analytical Computation of Critical Exponents in Several Holographic Superconductors

It is very interesting that all holographic superconductors, such as s-wave, p-wave and d-wave holographic superconductors, show the universal mean-field critical exponent 1/2 at the critical temperature, just like Gindzburg-Landau (G-L) theory for second order phase transitions. Now it is believed that the universal critical exponents appear because the dual gravity theory is classic in the large $N$ limit. However, even in the large $N$ limit there is an exception called "non-mean-field theory": an extension of the s-wave model with a cubic term of the charged scalar field shows a different critical exponent 1. In this paper, we try to use analytical methods to obtain the critical exponents for these models to see how the properties of the gravity action decides the appearance of the mean-field behaviors. It will be seen that just like the G-L theory, it is the fundamental symmetries rather than the detailed parameters of the bulk theory that lead to the universal properties of the holographic superconducting phase transition. The feasibility of the called "non-mean-field theory" is also discussed.

hep-th↗

Influence of a uniform magnetic field on dynamical chiral symmetry breaking in QED$_3$

We study dynamical chiral symmetry breaking (DCSB) in an effective QED$_{3}$ theory of d-wave high temperature cuprate superconductors under a uniform magnetic field. At zero temperature, the external magnetic field induces a mixed state by generating vortices in the condensate of charged holons. The growing magnetic field suppresses the superfluid density and thus reduces the gauge field mass which is opened via the Anderson-Higgs mechanism. By numerically solving the Dyson-Schwinger gap equation, we show that the massless fermions acquires a dynamical gap through DCSB mechanism when the magnetic field strength $H$ is above a critical value $H_{c}$ and the fermion flavors $N$ is below a critical value $N_{c}$. Further, it is found that both $N_{c}$ and the dynamical fermion gap increase as the magnetic field $H$ grows. It is expected that our result can be tested in phenomena in high temperature cuprate superconductors.

cond-mat.supr-con↗

Calculation of bulk viscosity of QCD at zero temperature and finite chemical potential

In this letter, based on Kubo's formula and the QCD low energy theorem, we propose a direct formula for calculating the bulk viscosity of QCD at finite chemical potential $μ$ and zero temperature. According to this formula, the bulk viscosity at finite $μ$ is totally determined by the dressed quark propagator at finite $μ$. We then use a dynamical, confining Dyson-Schwinger equation model of QCD to calculate the bulk viscosity at finite $μ$. It is found that no sharp peak behavior of the bulk viscosity at finite $μ$ is observed, which is quite different from that of the bulk viscosity at finite temperature.

hep-ph↗

A model study of quark number susceptibility at finite temperature beyond rainbow-ladder approximation

In this paper we calculate the quark number susceptibility (QNS) of QCD at finite temperature under the rainbow-ladder and Ball-Chiu type truncation schemes of the Dyson-Schwinger approach. It is found that the difference between the result of the rainbow-ladder truncation and that of Ball-Chiu type truncation is small, which shows that the dressing effect of the quark-gluon vertex on the QNS at finite temperature is small. It is also found that at low temperature the quark number susceptibility is nearly zero and it increases sharply when the temperature approaches the chiral phase transition point. A comparison between the result in the present paper with those in the literature is made.

hep-ph↗

Supercurrent in p-wave Holographic Superconductor

The p-wave and $p+ip$-wave holographic superconductors with fixed DC supercurrent are studied by introducing a non-vanishing vector potential. We find that close to the critical temperature $T_c$ of zero current, the numerical results of both the p wave model and the $p+ip$ model are the same as those of Ginzburg-Landau (G-L) theory, for example, the critical current $j_c \sim (T_c-T)^{3/2}$ and the phase transition in the presence of a DC current is a first order transition. Besides the similar results between both models, the $p+ip$ superconductor shows isotropic behavior for the supercurrent, while the p-wave superconductor shows anisotropic behavior for the supercurrent.

hep-th↗

Model Study of a Quark Star

In this paper we apply the equation of state (EOS) of QCD at finite chemical potential and zero temperature proposed in H. S. Zong and W. M. Sun [Int. J. Mod. Phys. {\bf A23}, 3591 (2008)] to the study of properties of quark star. This EOS contains only one adjustable parameter $m_D$ which sets the scale of chiral symmetry breaking (in our calculation we have chosen two values of $m_D$: $m_D=244 MeV$ and $m_D=239 MeV$, which is fitted from the value of $f_π$ and determined by $e^+ e^-$ annihilation experiment, respectively). From this EOS a model of quark star is established by applying the Tolman-Oppenheimer-Volkoff equation under two conditions: with the $P(μ=0)$ term and without the $P(μ=0)$ term. Our results show clearly that the $P(μ=0)$ term is an important quantity in the study of quark star. A comparison between our model and other models of quark star is made. In particular, we have compared our results with the most recent observational data measured using Shapiro delay reported in P.B. Demorest et al. [Nature (London) {\bf 467}, 1081 (2010)].

hep-ph↗

Characteristic length of a Holographic Superconductor with $d$-wave gap

After the discovery of the $s$-wave and $p$-wave holographic superconductors, holographic models of $d$-wave superconductor have also been constructed recently. We study analytically the perturbation of the dual gravity theory to calculate the superconducting coherence length $ξ$ of the $d$-wave holographic superconductor near the superconducting phase transition point. The superconducting coherence length $ξ$ divergents as $(1-T/T_c)^{-1/2}$ near the critical temperature $T_c$. We also obtain the magnetic penetration depth $λ\propto(T_c-T)^{-1/2}$ by adding a small external homogeneous magnetic field. The results agree with the $s$-wave and $p$-wave models, which are also the same as the Ginzburg-Landau theory.

hep-th↗