Quadrupole polarizabilities of the pion in the Nambu–Jona-Lasinio model

The electromagnetic dipole and quadrupole polarizabilities of the neutral and charged pions are calculated in the Nambu–Jona-Lasinio model. Our results agree with the recent experimental analysis of these quantities based on dispersion sum rules. Comparison is made with the results from the chiral perturbation theory.     

Time-dependent Ginzburg–Landau equation in the Nambu–Jona-Lasinio model

We apply the closed time-path Green function formalism in the Nambu–Jona-Lasinio model. First of all, we use this formalism to obtain the well-known gap equation for the quark condensate in a stationary homogeneous system. We have also used this formalism to obtain the Ginzburg–Landau (GL) equation and the time-dependent Ginzburg–Landau (TDGL) equation for the chiral order parameter in an inhomogeneous system. In our derived GL and TDGL equations, there is no other parameters except for those in the original NJL model.     

Low-energy processes of meson production in the extended Nambu–Jona-Lasinio model

The processes of meson production in electron–positron collisions at low energies are characterized within the extended Nambu–Jona-Lasinio model. It is demonstrated that intermediate vector mesons (both in the ground state and in the first radially excited one) play a critical part in these processes. The obtained results are in reasonable agreement with the available experimental data. A number of theoretical predictions are made, which can be tested experimentally in the near future.     

Chemical potentials and parity breaking: the Nambu–Jona-Lasinio model

Relying on the collinear factorization approach, we demonstrate that H1 and ZEUS measurements of exclusive light vector meson and photon electroproduction cross sections can be simultaneously described for photon virtualities of ${\mathcal {Q}}\gtrsim 2\, \mathrm{GeV}$ . Our findings reveal that quark exchanges are important in this small $x_\mathrm{Bj}$ region and that in leading order approximation the gluonic component is suppressed, e.g., the skewness ratio can be much smaller than one.     

Nonlocal Nambu–Jona-Lasinio model and chiral chemical potential

We derive the critical temperature in a nonlocal Nambu–Jona-Lasinio model with the presence of a chiral chemical potential. The model we consider uses a form factor derived from recent studies of the gluon propagator in Yang–Mills theory and has the property to fit in excellent way the form factor arising from the instanton liquid picture for the vacuum of the theory. Nambu–Jona-Lasinio model is derived form quantum chromodynamics providing all the constants of the theory without any need for fits. We show that the critical temperature in this case always exists and increases as the square of the chiral chemical potential. The expression we obtain for the critical temperature depends on the mass gap that naturally arises from Yang–Mills theory at low-energy as also confirmed by lattice computations.     

Chiral susceptibility and chiral phase transition in Nambu–Jona-Lasinio model

We give a general relation between the chiral susceptibility and the thermodynamical potential and a relation between the chiral susceptibility and the condition for furcations to appear in the Wigner solution(s) in the Nambu–Jona-Lasinio (NJL) model. We find that the chiral susceptibility is a quantity able to represent the appearance of furcation in the solution(s) of the gap equation and the concavo–convexity of the thermodynamical potential in the NJL model. It indicates that the chiral susceptibility can identify the stability of the states and the chiral phase transition in NJL model. We propose that analyzing the chiral susceptibility may play an important role in studying the chiral phase transition in approaches superior to the NJL model.     

On the Problem of Spontaneous Isotopic Symmetry Breaking in Nambu–Jona-Lasinio Models

Physics of Particles and Nuclei Letters - The problem of spontaneous isotopic symmetry breaking in Nambu–Jona-Lasinio quark models is considered. It is shown that, in models with light...     

Meson electro-magnetic form factors in an extended Nambu–Jona-Lasinio model including heavy quark flavors

Based on an extended NJL model including heavy quark flavors, we calculate the form factors of pseudoscalar and vector mesons. After taking into account the vector-meson-dominance effect, which introduces a form factor correction to the quark vector coupling vertices, the form factors and electric radii of π+and K+pseudo-scalar mesons in the light flavor sector fit the experimental data well. The magnetic moments of the light vector mesonsρ+and K*+are comparable with other theoretical calculations. The form factors in the light-heavy flavor sector are presented to compare with future experiments or other theoretical calculations.     

Nuclear matter and neutron star properties with the extendedNambu-Jona-Lasinio model

An extended Nambu-Jona-Lasinio(eNJL) model with nucleons as the degrees of freedom is used to investigate properties of nuclear matter and neutron stars(NSs),including the binding energy and symmetry energy of the nuclear matter, the core-crust transition density, and mass-radius relation of NSs. 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 obtained for a given nuclear incompressibility. It is shown that the isovector-vector interaction has a significant influence on the nuclear matter and NS properties, and the sign of isovector-vector coupling constant is critical in the determination of 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.     

Influence of the nuclear equation of state on the hadron-quark phase transition in neutron stars

We study the hadron-quark phase transition in the interior of neutron stars, and examine the influence of the nuclear equation of state on the phase transition and neutron star properties. The relativistic mean field theory with several parameter sets is used to construct the nuclear equation of state, while the     

Parity violation,the neutron radius of lead,and neutron stars

The neutron radius of a heavy nucleus is a fundamental nuclear-structure observable that remains elusive. Progress in this arena has been limited by the exclusive use of hadronic probes that are hindered by large and controversial uncertainties in the reaction mechanism. The parity radius experiment at the Jefferson Laboratory offers an attractive electro-weak alternative to the hadronic program and promises to measure the neutron radius of ²⁰⁸Pb accurately and model independently via parity-violating electron scattering. In this contribution we examine the far-reaching implications that such a determination will have in areas as diverse as nuclear structure, atomic parity violation, and astrophysics.     

双中子星的星族合成研究

双中子星是天体物理中重要的研究对象,对于许多研究领域都有重要作用。2017年LIGO/Virgo发现第一个双中子星并合事件GW170817,开启了用引力波探测发现双中子星的序幕。文章主要介绍了双中子星的双星演化通道,以及双中子星星族合成的一些性质。此外,还介绍了双星演化中的一些不确定性以及形成GW170817双中子星的双星演化通道。     

Searching for gravitational waves from rotating neutron stars

Rotating neutron stars are one of the important sources of gravitational waves (GW) for the ground based as well as space based detectors. Since the waves are emitted continuously, the source is termed as a continuous gravitational wave (CGW) source. The expected weakness of the signal requires long integration times (∼year). The data analysis problem involves tracking the phase coherently over such large integration times, which makes it the most computationally intensive problem among all GW sources envisaged. In this article, the general problem of data analysis is discussed, and more so, in the context of searching for CGW sources orbiting another companion object. The problem is important because there are several pulsars, which could be deemed to be CGW sources orbiting another companion star. Differential geometric techniques for data analysis are described and used to obtain computational costs. These results are applied to known systems to assess whether such systems are detectable with current (or near future) computing resources.     

Effects of relativistic parameter sets on tidal deformabilities and f-mode oscillations of neutron stars

The implications of relativistic parameter sets established at saturation density on the tidal deformabilities and f-mode oscillations of neutron stars (NSs) are examined using constraints from the gravitational wave (GW) event GW170817 and NICER. According to our findings, the isovector saturation parameters have a greater impact on the radii and tidal deformabilities of NSs than the isoscalar saturation parameters. Our analysis also examines the impact of saturation properties on f-mode frequencies and finds that f-mode frequencies with 1.4 M_⊙ (solar mass) are roughly between 1.95 and 2.15 kHz. These findings could be confirmed by future advanced GW detectors. A good linear parameter-independent correlation between f-mode frequencies inferred from saturation parameters in the entire region is also observed, and we attempt to fit an updated version of this universal relationship. Furthermore, we used chiral effective theory (χEFT) together with the multi-messenger astronomy constraints to further reinforce the rationality of the conclusions we have reached.     

Crust-core transition and dynamical instabilities in neutron stars for model with point-coupling interactions

We explore the effects of the density dependence of symmetry energy on the crust-core phase transition and dynamical instabilities in cold and warm neutron star...     

Hypernuclear physics for neutron stars

The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon–nucleon and hyperon–hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Nonmesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars.