arXiv subjects

Hong-Shi Zong

Publications and source records attributed to Hong-Shi Zong.

At least 37 records · Page 2Linked to original sources

arXiv2020

The contributions of the vector-channel at finite isospin chemical potential with the self-consistent mean field approximation

The self-consistent mean field approximation of two-flavor NJL model, which introduces a free parameter $α$ ($α$ reflects the weight of different interaction channels), is employed to investigate the contributions of the vector-channel at finite isospin chemical potential $μ_I$ and zero baryon chemical potential $μ_B$ and zero temperature $T$. The calculations show that the consideration of the vector-channel contributions leads to lower value of pion condensate in superfluid phase, compared with the standard Lagrangian of NJL model ($α=0$). In superfluid phase, we also obtain lower isospin number density, and the discrepancy is getting larger with the increase of isospin potential. Compared with the recent results from Lattice QCD, the isospin density and energy density we obtained with $α=0.5$ agree with the data of lattice well. In the phase diagram in the $T-μ_I$ plane for $μ_B=0$, we can see that the difference of the critical temperatures of phase transition between the results with $α=0$ and $α=0.5$ is up to $3\%-5\%$ for a fixed isospin potential. All of these indicate that the vector channels play an important role in isospin medium.

hep-ph↗

arXiv2020

Effective dynamics for a spin-1/2 particle constrained to a space curve in an electric and magnetic field

We consider the dynamics of a spin-1/2 particle constrained to move in an arbitrary space curve with an external electric and magnetic field applied. With the aid of gauge theory, we successfully decouple the tangential and normal dynamics and derive the effective Hamiltonian. A new type of quantum potential called SU(2) Zeeman interaction appears, which is induced by the electric field and couples spin and intrinsic orbital angular momentum. Based on the Hamiltonian, we discuss the spin precession for zero intrinsic orbital angular momentum case and the energy splitting caused by the SU(2) Zeeman interaction for a helix as examples, showing the combined effect of geometry and external field. The new interaction may bring new approaches to manipulate quantum states in spintronics.

cond-mat.mes-hall↗

arXiv2020

Spin polarization of electrons through corrugated surface in magnetic field

Noninteracting electrons confined to a corrugated surface are investigated in magnetic field, and the associated effective Pauli equation is given analytically by the thin-layer quantization scheme. Interestingly, the Zeeman splitting gaps can be adjusted by curvature, and there is a geometric potential induced by curvature. Further, we discuss the spin-dependent transport properties for confined electrons by numerical calculation. More interestingly, we find that the spin polarization induced by curvature becomes substantial when the incident energy has small value. The results are considerable for a spin transistor with small spin current.

cond-mat.mes-hall↗

arXiv2019

Non-strange quark stars from NJL model with proper-time regularisation

The structure of light quark star is studied within a new two-flavor NJL model. By retaining the contribution from the vector term in the Fierz-transformed Lagrangian, a two-solar-mass pure quark star is achieved. To overcome the disadvantage of three-momentum truncation in the regularisation procedure, we introduce the proper-time regularisation. We also employ the newly proposed definition of vacuum pressure, in which the quasi-Wigner vacuum (corresponding to the quasi-Winger solution of the gap equation) is used as the reference ground state. Free parameter includes only a mixing constant $α$ which weighs contribution from Fierz-transformed Lagrangian. We constrain $α$ to be around $0.9$ by the observed mass of pulsars $PSR J0348+0432$ and $PSR J1614-2230$. We find the calculated surface energy density meets the requirement ($> 2.80\times10^{14}$g/cm$^3 $). Besides, for a 1.4 solar mass star, the tidal Love number $k_2$ and deformability $Λ$ are calculated which satisfies the constrain $200 < Λ< 800$.

hep-ph↗

arXiv2019

Cosmic Acceleration Caused by the Extra-Dimensional Evolution in a Generalized Randall-Sundrum Model

We investigate a $(n+1)$-dimensional generalized Randall-Sundrum model with an anisotropic metric which has three different scale factors. One obtain a positive effective cosmological constant $Ω_{eff}\sim10^{-124}$ (in Planck unit) which only need a solution $kr\simeq50-80$ without fine tuning, and both the visible and hidden brane tensions are positive which results in the two branes to be stable. Then, we find that the Hubble parameter is seem to be a constant in a large region near its minimum, thus causing the acceleration of the universe. Therefore, the fine tuning problem also can be solved in this model. Meanwhile, the scale of extra dimensions is smaller than the observed scale but greater than the Planck length. This demonstrates that the observed present acceleration of the universe is caused by the extra-dimensional evolution rather than dark energy.

gr-qc↗

arXiv2019

Elastic electromagnetic form factors of vector mesons

A symmetry-preserving approach to the two valence-body continuum bound-state problem is used to calculate the elastic electromagnetic form factors of the $ρ$-meson and subsequently to study the evolution of vector-meson form factors with current-quark mass. To facilitate a range of additional comparisons, $K^\ast$ form factors are also computed. The analysis reveals that: vector mesons are larger than pseudoscalar mesons; composite vector mesons are non-spherical, with magnetic and quadrupole moments that deviate $\sim 30$\% from point-particle values; in many ways, vector-meson properties are as much influenced by emergent mass as those of pseudoscalars; and vector meson electric form factors possess a zero at spacelike momentum transfer. Qualitative similarities between the electric form factors of the $ρ$ and the proton, $G_E^p$, are used to argue that the character of emergent mass in the Standard Model can force a zero in $G_E^p$. Morover, the existence of a zero in vector meson electric form factors entails that a single-pole vector meson dominance model can only be of limited use in estimating properties of off-shell vector mesons, providing poor guidance for systems in which the Higgs-mechanism of mass generation is dominant.

nucl-th↗

arXiv2019

QCD phase diagram in chiral imbalance with self-consistent mean field approximation

We employ a new self-consistent mean field approximation of NJL model, which introduces a free parameter $α$ ($α$ reflects the weight of different interaction channels), to study the effects of the chiral chemical potential $μ_5$ on QCD phase structure, especially the location of the QCD critical end point (CEP). We find that, at a high temperature, the critical temperature of QCD phase transition smoothly increases with $μ_5$ at the beginning, and then decreases rapidly. At low temperature and high baryon density region, the increase of the chiral chemical potential will reduce the critical chemical potential of phase transition. The temperature of the CEP shows a non-monotonic dependence on the chiral chemical potential with a long plateau around the maximum. At $μ_5=0$, we found that the CEP will disappear when the $α$ value is larger than 0.71 and will reappear when the $μ_5$ increases. This study is important for exploring the QCD phase structure and the location of CEP in chiral imbalanced systems.

nucl-th↗

arXiv2019

The geometric potential of a double-frequency corrugated surface

For an electron confined to a surface reconstructed by double-frequency corrugations, we give the effective Hamiltonian by the formula of geometric influences, obtain an additive scalar potential induced by curvature that consists of attractive wells with different depth. The difference is generated by the multiple frequency of the double-frequency corrugation. Subsequently, we investigate the effects of geometric potential on the transmission probability, and find the resonant tunneling peaks becoming rapidly sharper and the transmission gaps being substantially widened with increasing the multiple frequency. As a potential application, double-frequency corrugations can be employed to select electrons with particular incident energy, as an electronic switch, which are more effective than a single-frequency ones.

cond-mat.mes-hall↗

arXiv2019

Geometric effects on the electronic structure and the bound states in annular corrugated wires

In the spirit of the thin-layer quantization scheme, we give the effective Hamiltonian describing the noninteracting electrons confined to an annular corrugated surface, and find that the geometrically induced potential is considerably influenced by corrugations. By using numerical calculation, we investigate the eigenenergies and the corresponding eigenstates, and find that the transition energies can be sufficiently improved by adding corrugations. Particularly, the transition energy between the adjacent eigenstates corresponds to energy levels difference based on the wavefunction of annular wire, and the number of the energy levels is equal to the number of corrugations. And the larger magnitude of corrugations is capable of increasing the number of bound states. In addition, the distribution of ground state probability density is reconstructed by the corrugations, and the energy shift is generated.

cond-mat.mes-hall↗

arXiv2019

Geometric effects of a quarter of corrugated torus

In the spirit of the thin-layer quantization scheme, we give the effective Shrödinger equation for a particle confined to a corrugated torus, in which the geometric potential is substantially changed by corrugation. We find the attractive wells reconstructed by the corrugation not being at identical depths, which is strikingly different from that of a corrugated nanotube, especially in the inner side of the torus. By numerically calculating the transmission probability, we find that the resonant tunneling peaks and the transmission gaps are merged and broadened by the corrugation of the inner side of torus. These results show that the quarter corrugated torus can be used not only to connect two tubes with different radiuses in different directions, but also to filter the particles with particular incident~energies.

cond-mat.mes-hall↗

arXiv2019

Fine Tuning Problem of the Cosmological Constant in a Generalized Randall-Sundrum Model

To solve the cosmological constant fine tuning problem, we investigate a $(n+1)$-dimensional generalized Randall-Sundrum brane world scenario with two $(n-1)$-branes instead of two 3-branes. Adopting an anisotropic metric ansatz, we obtain the positive effective cosmological constant $Ω_{eff}$ of order $10^{-124}$ and only require a solution $\simeq50-80$. Meanwhile, both the visible and hidden branes are stable because their tensions are positive. Therefore, the fine tuning problem can be solved quite well. Furthermore, the Hubble parameter $H_{1}(z)$ as a function of redshift $z$ is in good agreement with cosmic chronometers dataset. The evolution of the universe naturally shifts from deceleration to acceleration. This demonstrates that the evolution of the universe is intrinsically an extra-dimensional phenomenon. It can be seen as a dynamic model of dark energy which is driven by the evolution of the extra dimensions on the brane.

gr-qc↗

arXiv2019

Close-in Exoplanets as Candidates of Strange Quark Matter Objects

Since the true ground state of the hadrons may be strange quark matter (SQM), pulsars may actually be strange stars rather than neutron stars. According to this SQM hypothesis, strange planets can also stably exist. The density of normal matter planets can hardly be higher than 30 g cm$^{-3}$. As a result, they will be tidally disrupted when its orbital radius is less than $\sim 5.6\times10^{10} \rm \, cm $, or when the orbital period ($P_{\rm orb}$) is less than $ \sim \rm 6100\, s $. On the contrary, a strange planet can safely survive even when it is very close to the host, due to its high density. The feature can help us identify SQM objects. In this study, we have tried to search for SQM objects among close-in exoplanets orbiting around pulsars. Encouragingly, it is found that four pulsar planets (XTE J1807-294 b, XTE J1751-305 b, PSR 0636 b, PSR J1807-2459A b) completely meet the criteria of $P_{\rm orb} < \rm 6100\, s $, and are thus good candidates for SQM planets. The orbital periods of two other planets (PSR J1719+14 b and PSR J2051-0827 b) are only slightly higher than the criteria. They could be regarded as potential candidates. Additionally, we find that the periods of five white dwarf planets (GP Com b, V396 Hya b, J1433 b, WD 0137-349 b, and SDSS J1411+2009 b) are less than 0.1 days. We argue that they might also be SQM planets. It is further found that the persistent gravitational wave emissions from at least three of these close-in planetary systems are detectable to LISA. More encouragingly, the advanced LIGO and Einstein Telescope are able to detect the gravitational wave bursts produced by the merger events of such SQM planetary systems, which will provide a unique test for the SQM hypothesis.

astro-ph.HE↗

arXiv2019

Do the current astronomical observations exclude the existence of non-strange quark stars?

As is pointed out in a recent work (Phys. Rev. Lett. 120, 222001), quark matter may not be strange. Inspired by this argument, we use a new self-consistent mean field approximation method to study the equation of state of cold dense matter within the framework of the two-flavor NJL model. Then the mass-radius relationship of two-flavor pure quark stars is studied. In the new self-consistent mean field approximation method we introduced, there is a free parameter $α$, which reflects the weight of different interaction channels. In principal, $α$ should be determined by experiments rather than the self-consistent mean field approximation itself. In this paper, thus, the influence of the variation of $α$ on the critical chemical potential of chiral phase transition and the stiffness of the EOS are thoroughly explored. It is found that the stiffness of EOS can be increased greatly to support a two-solar-mass pure quark star when $α$ is greater than 0.95. This means that current theoretical calculations and astronomical observations cannot rule out the possibility of a two-flavor pure quark star.

nucl-th↗

arXiv2019

Anisotropic evolution of 4-brane in a 6D generalized Randall-Sundrum model

We investigate a 6d generalized Randall-Sundrum brane world scenario with a bulk cosmological constant. It is shown that each stress-energy tensor $T_{ab}^{i}$ on the brane is similar to a constant vacuum energy. This is consistent with the Randall-Sundrum model in which each 3-brane Lagrangian separated out a constant vacuum energy. By adopting an anisotropic metric ansatz, we obtain the 5d Friedmann-Robertson-Walker field equations. At a little later period, the expansion of the universe is proportional to $t^{\frac{1}{2}}$ which is as similar as the period of the radiation-dominated. We also investigate the case with two $a(t)$ and two $b(t)$. In a large region of $t$, we obtain the 3d effective cosmological constant $Λ_{eff}=-2Ω/3>0$ which is independent of the integral constant. Here the scale factor is exponential expansion which is consistent with our present observation of the universe. Our results demonstrate that it is possible to construct a model which solves the dark energy problem, meanwhile guaranteeing a positive brane tension.

gr-qc↗

arXiv2019

Transition form factors: $γ^\ast + p \to Δ(1232)$, $Δ(1600)$

Electroproduction form factors describing the $γ^\ast p \to Δ^+(1232), Δ^+(1600)$ transitions are computed using a fully-dynamical diquark-quark approximation to the Poincaré-covariant three-body bound-state problem in relativistic quantum field theory. In this approach, the $Δ(1600)$ is an analogue of the Roper resonance in the nucleon sector, appearing as the simplest radial excitation of the $Δ(1232)$. Precise measurements of the $γ^\ast p \to Δ^+(1232)$ transition already exist on $0 \leq Q^2 \lesssim 8\,$GeV$^2$ and the calculated results compare favourably with the data outside the meson-cloud domain. The predictions for the $γ^\ast p \to Δ^+(1600)$ magnetic dipole and electric quadrupole transition form factors are consistent with the empirical values at the real photon point, and extend to $Q^2 \approx 6 m_p^2$, enabling a meaningful direct comparison with experiment once analysis of existing data is completed. In both cases, the electric quadrupole form factor is particularly sensitive to deformation of the $Δ$-baryons. Interestingly, whilst the $γ^\ast p \to Δ^+(1232)$ transition form factors are larger in magnitude than those for $γ^\ast p \to Δ^+(1600)$ in some neighbourhood of the real photon point, this ordering is reversed on $Q^2 \gtrsim 2 m_p^2$, suggesting that the $γ^\ast p \to Δ^+(1600)$ transition is more localised in configuration space.

nucl-th↗

arXiv2019

New algorithm to study the pseudo-Wigner solution of the quark gap equation in the framework of the (2+1)-flavor NJL model

In this paper, we study the pseudo-Wigner solution of the quark gap equation with a recently proposed algorithm in the framework of the (2+1)-flavor Nambu-Jona-Lasinio (NJL) model. We find that for the current quark mass $m_{\rm u,d}=5.5$ MeV and chemical potential $μ<μ_{\rm TCP}=272.5$ MeV, the Nambu solution and the positive pseudo-Wigner solution obtained via this algorithm is consistent with the physical solution obtained with the iterative method. Furthermore, the algorithm we used can help to illustrate the evolution of the solutions of the gap equation from the chiral limit to non-chiral limit and gives a prediction where the crossover line is located in the phase diagram for $μ<272.5$ MeV. In addition, we also study the chiral susceptibilities as well as the loss of solutions for different chemical potentials.

hep-ph↗

arXiv2019

Chiral phase transition from the Dyson-Schwinger equations in a finite spherical volume

Within the framework of Dyson-Schwinger equations and by means of Multiple Reflection Expansion, we study the finite volume effects on the chiral phase transition in a sphere, especially discuss its influence on the location of the possible critical end point (CEP). According to our calculations, when we take the sphere instead of cube as a research, the influence of finite volume effects on phase transition is not as significant as previously calculated. For instance, as the radius of spherical volume decreases from infinite to $2 \mathrm{fm}$, at zero chemical potential and finite temperature, the critical temperature $T_{c}$ has only a slight drop. And at finite chemical potential and finite temperature, the location of CEP shifts toward smaller temperature and higher chemical potential, but the amplitude of variation does not exceed $20\%$. So we find that not only the size of the volume, but also the shape of the volume will have a considerable impact on the phase transition.

hep-ph↗

arXiv2019

Geometrical phase and Hall effect associated with the transverse spin of light

By analyzing the vectorial Helmholtz equation within the thin-layer approach, we find that light acquires a novel geometrical phase, in addition to the usual one (the optical Berry phase), during the propagation along a curved path. Unlike the optical Berry phase, the novel geometrical phase is induced by the transverse spin along the binormal direction and associated with the curvature of the curve. Furthermore, we show a novel Hall effect of light induced by the torsion of the curve and associated with the transverse spin along the binormal direction, which is different from the usual spin Hall effect of light. Finally, we demonstrate that the usual and novel geometrical phase phenomena are described by different geometry-induced U(1) gauge fields in different adiabatic approximations. In the nonadiabatic case, these gauge fields are united in one effective equation by SO(3) group.

physics.optics↗