From masses and radii of neutron stars to EOS of nuclear matter through neural network

The equation of state(EOS)of dense nuclear matter is a key factor for determining the internal structure and properties of neutron stars.However,the EOS of high-density nuclear matter has great uncertainty,mainly because terrestrial nuclear experiments cannot reproduce matter as dense as that in the inner core of a neutron star.Fortunately,continuous improvements in astronomical observations of neutron stars provide the opportunity to inversely constrain the EOS of high-density nuclear matter.Several methods have been proposed to implement this inverse constraint,including the Bayesian analysis algorithm,the Lindblom’s approach,and so on.Neural network algorithm is an effective method developed in recent years.By employing a set of isospin-dependent parametric EOSs as the training sample of a neural network algorithm,we set up an effective way to reconstruct the EOS with relative accuracy using a few mass-radius data.Based on the obtained neural network algorithms and according to the NICER observations on masses and radii of neutron stars with assumed precision,we obtain the inversely constrained EOS and further calculate the corresponding macroscopic properties of the neutron star.The results are basically consistent with the constraint on EOS in Huth et al.[Nature 606,276(2022)]based on Bayesian analysis.Moreover,the results show that even though the neural network algorithm was obtained using the finite parameterized EOS as the training set,it is valid for any rational parameter combination of the parameterized EOS model.

Distinguishing the observational signatures of hot spots orbiting Reissner-Nordström spacetime

This paper investigates observable signatures of hot spots orbiting Reissner-Nordström(RN)black holes and naked singularities.For an RN black hole,we find two discernible lensing image tracks in time integrated images,capturing a complete orbit of hot spots and a image shadow within the critical curve where photons with a small impact parameter fall into the event horizon.Conversely,in RN singularities,additional image tracks can be found within the critical curve,originating from photons reflected by the infinitely high effective potential well.Moreover,we find incomplete and converging tracks from the time integrated images of hot spot orbiting RN singularities that have no photon sphere.The presence of these additional image tracks significantly influences temporal magnitudes at their local maxima,enabling us to differentiate between RN black holes and RN naked singularities.

U(1)Lμ-Lτ breaking phase transition, muon g–2, dark matter, collider, and gravitational wave

Combining the dark matter and muon g-2 anomaly,we study the U(1)Lμ-Lτbreaking phase transition,gravitational wave spectra,and direct detection at the LHC in an extra U(1)Lμ-Lτgauge symmetry extension of the standard model.The new fields include vector-like leptons(E1,E2,N),the U(1)Lμ-Lτbreaking scalar S,and the gauge boson Z’,as well as the dark matter candidate XI and its heavy partner XR.A joint explanation of the dark matter relic density and muon g-2 anomaly excludes the region where both min(mE1,mE2,mN,mXR)and min(mZ’,mS)are much larger than mXI.In the parameter space accommodating the DM relic density and muon g-2 anomaly,the model can achieve a first-order U(1)Lμ-Lτbreaking phase transition,whose strength is sensitive to the parameters of the Higgs potential.The corresponding gravitational wave spectra can reach the sensitivity of UDECIGO.In addition,the direct searches at the LHC impose stringent bounds on the mass spectra of the vector-like leptons and dark matter.

Production of higher excited quarkonium pair at the super Z factory

The heavy constituent quark pair of the heavy quarkonium is produced perturbatively and subsequently undergoes hadronization into the bound state non-perturbatively.The production of the heavy quarkonium is essential to testing our understanding of quantum chromodynamics(QCD)in both perturbative and non-perturbative aspects.The electron-positron collider will provide a suitable platform for the precise study of the heavy quarkonium.The higher excited heavy quarkonium may contribute significantly to the ground states,which should be considered for sound estimation.We study the production rates of the higher excited states quarkonium pair in■at the future Z factory under the non-relativistic QCD(NRQCD)framework,where the■represents the color-singlet states■The differential angle distribution of cross sections■is given.We also discuss the uncertainties of cross sections caused by the varying quark masses and the renormalization scaleμ.We show that significant numbers of events for pairs of higher excited state quarkonia can be generated at the super Z factory.

Neutrino oscillations in the Non-Kerr black hole with quantum phenomenon

In this study,we have investigated the mathematical components of the Dirac equation in curved spacetime and how they can be applied to the analysis of neutrino oscillations.More specifically,we have developed a method for calculating the phase shift in flavor neutrino oscillations by utilizing a Taylor series expansion of the action that takes into account△m^(4) orders.In addition,we have used this method to assess how the phase difference in neutrino mass eigenstates changes according to the gravitational field described by the Johannsen spacetime.