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Evaluating topological charge density with symmetric multi-probing method
Guang-Yi Xiong, Jian-Bo Zhang, You-Hao Zou
Published:   , doi: 10.1088/1674-1137/43/3/033102
We evaluated the topological charge density of SU(3) gauge fields on lattice by calculating the trace of overlap Dirac matrix employing symmetric multi-probing(SMP) method with 3 modes. Since the topological charge Q for a given lattice configuration must be an integer number, it's easy to estimate the systematic error (the deviation of Q to nearest integer). The results showed high efficiency and accuracy in calculating the trace of the inverse of a large sparse matrix with locality by using SMP sources, compared with that using point sources. We also showed the correlation between the errors and probing scheme parameter \begin{document}$r_{\min}$\end{document} as well as lattice volume \begin{document}$N_{L}$\end{document} and lattice spacing a. It was found that the computing time of calculating the trace by employing SMP sources is less dependent on \begin{document}$N_{L}$\end{document} than that by using point sources. Therefore the SMP method is very suitable for calculations on large lattices.
Probing the QCD phase structure with higher order baryon number susceptibilities within the NJL model
Wenkai Fan, Xiaofeng Luo, Hongshi Zong
Published:   , doi: 10.1088/1674-1137/43/3/033103
Conserved charge fluctuations can be used to probe the phase structure of the strongly interacting nuclear matter in relativistic heavy-ion collisions. To obtain the characteristic signatures of the conserved charge fluctuations for the QCD phase transition, we perform a detailed study on the susceptibilities of dense quark matter up to 8th order by using an effective QCD based model. We studied two cases, one with the QCD critical end point (CEP) and one without due to an additional vector interaction term. The higher order susceptibilities display rich structures near the CEP and show sign changes as well as large fluctuations. These can provide us information about the presence and location of the CEP. Furthermore, we find that the case without the CEP also show similar sign change pattern, but with relatively smaller magnitude comparing to the case with the CEP. Finally, we conclude that higher order susceptibilities of conserved charge can be used to probe the QCD phase structures in heavy-ion collisions.
On matrix method for black hole quasinormal modes
Kai Lin, Wei-Liang Qian
Published:   , doi: 10.1088/1674-1137/43/3/031001
In this paper, we provide a comprehensive survey of possible applications of the matrix method for black hole quasinormal modes. The proposed algorithm can generally be applied to various background metrics, and in particular, it accommodates for both analytic and numerical forms of the tortoise coordinates, as well as black hole spacetimes. Our discussions give a detailed account of different types of black hole metrics, master equations, and the corresponding boundary conditions. Besides, we argue that the method can readily be applied to cases where the master equation is a system of coupled equations. By adjusting the number of interpolation points, the present method provides a desirable degree of precision, in reasonable balance with its efficiency. The method is flexible and can easily be adopted by various distinctive physical scenarios.
Fermion scattering by a class of Bardeen black holes
Ciprian A. Sporea
Published:   , doi: 10.1088/1674-1137/43/3/035104
In this paper the scattering of fermions by a class of Bardeen black holes is investigated. After obtaining the scattering modes by solving the Dirac equation in this geometry, we use the partial wave method to derive an analytical expression for the phase shifts that enter into the definitions of partial amplitudes that define the scattering cross sections and the induced polarization. It is then shown that, like in the case of Schwarzschild and Reissner-Nordström, the phenomena of glory and spiral scattering are present.
Finite volume effects on QCD chiral phase transition with finite size dependent Nambu-Jona-Lasinio model
Yonghui Xia, Qingwu Wang, Hongtao Feng, Hongshi Zong
Published:   , doi: 10.1088/1674-1137/43/3/034101
In principle, the effective Lagrangian of the finite volume system should depend on the system size. To this end, in the framework of Nambu-Jona-Lasinio (NJL) model, by considering the influence of quark feedback on the effective coupling, we obtain a modified NJL model and it's Lagrangian depends on the volume. Based on the modified NJL model, we study the influence of the finite volume effect on the chiral phase transition at finite temperature, and find that the pseudo-critical temperature of crossover is much lower than the corresponding pseudo-critical temperature obtained by the normal NJL model. This clearly reflects that the volume dependent effective Lagrangian plays an important role in the chiral phase transitions at finite temperature.
Charged scalar fields in a Kerr-Sen black hole: exact solutions, Hawking radiation and resonant frequencies
H. S. Vieira, V. B. Bezerra
Published:   , doi: 10.1088/1674-1137/43/3/035102
We consider charged massive scalar fields around a Kerr-Sen spacetime. The radial and angular parts of the covariant Klein-Gordon equation are solved in terms of the confluent Heun function. From the exact radial solution, we obtain the Hawking radiation spectrum and discuss the resonant frequencies. The massless case of the resonant frequencies is also examined.
Testing the fidelity of Gaussian processes for cosmography
Huan Zhou, Zhengxiang Li
Published:   , doi: 10.1088/1674-1137/43/3/035103
The dependence of implications from observations on cosmological models is an intractable problem not only in cosmology, but also sometimes in astrophysics. Gaussian processes, a powerful nonlinear interpolating tool without assuming a model or parametrization, has been widely used in directly reconstructing functions from observational data (e.g., expansion rate and distance measurements) for cosmography. However, the fidelity of this reconstructing method has never been checked. In this paper, we test the fidelity of Gaussian processes for cosmography by mocking observational data sets comprising different number of events with various uncertainty level. It is suggested that both these two factors are of great importance for the fidelity of reconstruction. That is, for expansion rate measurements, Gaussian processes is valid for reconstructing functions of Hubble parameter versus redshift when the number of observed events is as many as 256 and the uncertainty of data reaches to ~ 3%. Moreover, the distance-redshift relation reconstructed from observations of the upcoming Dark Energy Survey type Ia supernovae is credible.
Nuclear matter and neutron star properties with the extended Nambu-Jona-Lasinio model
Yan-Jun Chen
Published:   , doi: 10.1088/1674-1137/43/3/035101
An extended Nambu-Jona-Lasinio (eNJL) model with nucleons as the degrees of freedom is used to explore properties of nuclear matter and neutron stars, including the binding energy and symmetry energy of nuclear matter, the core-crust transition density and mass-radius relation of neutron stars. The fourth-order symmetry energy at saturation density is also investigated. When the bulk properties of nuclear matter at saturation density are used to determine the model parameters, the double solutions of parameters are found for a given nuclear incompressibility. It is shown that the influences of the isovector-vector interaction on the nuclear matter and neutron star properties are significant and the sign of isovector-vector coupling constant is critical to determine the trend of the symmetry energy and equation of state. The effects of the other model parameters and symmetry energy slope at saturation density are discussed.
Leptogenesis via Varying Weinberg Operator: a Semi-Classical Approach
Silvia Pascoli, Jessica Turner, Ye-Ling Zhou
Published:   , doi: 10.1088/1674-1137/43/3/03310
In this Letter, we introduce leptogenesis via a varying Weinberg operator from a semi-classical perspective. This mechanism is motivated by the breaking of an underlying symmetry which triggers a phase transition that causes the coupling of the Weinberg operator to become dynamical. Consequently, a lepton anti-lepton asymmetry arises from the interference of the Weinberg operator at two different spacetime points. Using this semi-classical approach, we treat the Higgs as a background field and show a reflection asymmetry between the leptons and anti-leptons is generated in the vicinity of the bubble wall. We solve the equations of motion of the lepton and anti-lepton quasiparticles to obtain the final lepton asymmetry.
Potential of octant degeneracy resolution in JUNO
M.V. Smirnov, Zhoujun HU, Shuaijie LI, Jiajie LING
Published:   , doi: 10.1088/1674-1137/43/3/033001
This research continues to focus on the idea using cyclotronic antineutrino source for purposes of neutrino physics. Long baseline experiments suffer from degeneracies and correlations between \begin{document}$ \Theta_{23} $\end{document} , \begin{document}$ \delta_{\rm CP} $\end{document} and the mass hierarchy. However the combination of a superconductive cyclotron and a big liquid scintillator detector like JUNO in a medium baseline experiment, which doesn't depend on the mass hierarchy, may allow us to determine whether the position of the mixing angle \begin{document}$ \Theta_{23} $\end{document} is in the lower octant or the upper octant. Such an experiment would improve the precision of the \begin{document}$ \Theta_{23} $\end{document} measurement to a degree which depends on the CP-phase.