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 Select Comparison of Proton Shower Developments in the BGO Calorimeter of the Dark Matter Particle Explorer between GEANT4 and FLUKA Simulations Wei Jiang, Chuan Yue, Ming-Yang Cui, Xiang Li, Qiang Yuan, Francesca Alemanno, Paolo Bernardini, Giovanni Catanzani, Zhan-Fang Chen, Ivan De Mitri, Tie-Kuang Dong, Giacinto Donvito, David Francois Droz, Piergiorgio Fusco, Fabio Gargano, Dong-Ya Guo, Dimitrios Kyratzis, Shi-Jun Lei, Yang Liu, Francesco Loparco, Peng-Xiong Ma, Giovanni Marsella, Mario Nicola Mazziotta, Xu Pan, Wen-Xi Peng, Antonio Surdo, Andrii Tykhonov, Yi-Yeng Wei, Yu-Hong Yu, Jing-Jing Zang, Ya-Peng Zhang, Yong-Jie Zhang, and Yun-Long Zhang Chin. Phys. Lett.    2020, 37 (11): 119601 .   DOI: 10.1088/0256-307X/37/11/119601 Abstract   HTML   PDF (1020KB) The DArk Matter Particle Explorer (DAMPE) is a satellite-borne detector for high-energy cosmic rays and $\gamma$-rays. To fully understand the detector performance and obtain reliable physical results, extensive simulations of the detector are necessary. The simulations are particularly important for the data analysis of cosmic ray nuclei, which relies closely on the hadronic and nuclear interactions of particles in the detector material. Widely adopted simulation softwares include the GEANT4 and FLUKA, both of which have been implemented for the DAMPE simulation tool. Here we describe the simulation tool of DAMPE and compare the results of proton shower properties in the calorimeter from the two simulation softwares. Such a comparison gives an estimate of the most significant uncertainties of our proton spectral analysis.
 Select Neutrino Emission and Cooling of Dark-Matter-Admixed Neutron Stars Wen-Bo Ding, Zi Yu, Yan Xu, Chun-Jian Liu, Tmurbagan Bao Chin. Phys. Lett.    2019, 36 (4): 049701 .   DOI: 10.1088/0256-307X/36/4/049701 Abstract   HTML   PDF (632KB) The GW170817 binary neutron star merger event in 2017 has raised great interest in the theoretical research f neutron stars. The structure and cooling properties of dark-matter-admixed neutron stars are studied here using relativistic mean field theory and cooling theories. The non-self-annihilating dark matter (DM) component is assumed to be ideal fermions, among which the weak interaction is considered. The results show that pulsars J1614-2230, J0348+0432 and EXO 0748-676 may all contain DM with the particle mass of 0.2–0.4 GeV. However, it is found that the effect of DM on neutron star cooling is complicated. Light DM particles favor the fast cooling of neutron stars, and the case is converse for middle massive DM. However, high massive DM particles, around 1.0 GeV, make the low mass (around solar mass) neutron star still undergo direct Urca process of nucleons at the core, which leads the DM-admixed stars cool much more quickly than the normal neutron star, and cannot support the direct Urca process with a mass lower than 1.1 times solar mass. Thus, we may conjecture that if small (around solar mass) and super cold (at least surface temperature 5–10 times lower than that of the usual observed data) pulsars are observed, then the star may contain fermionic DM with weak self-interaction.
 Select Gravitational constant in f(R) theories of gravity with non-minimal coupling between matter and geometry Jun Wang, Li-Jia Cao Chin. Phys. Lett.    2018, 35 (12): 129801 .   DOI: 10.1088/0256-307X/35/12/129801 Abstract   HTML   PDF (530KB) We study the effect of the non-minimal coupling between matter and geometry on the gravitational constant in the context of $f(R)$ theories of gravity on cosmic scales. For a class of $f(R)$ models, the result shows that the value of the gravitational constant not only changes over time but also has the dampened oscillation behavior. Compared with the result of the standard ${\it \Lambda}$CDM model, the consequence suggests that the coupling between matter and geometry should be weak.
 Select Effect of Kinetic Alfvén Waves on Electron Transport in an Ion-Scale Flux Rope Bin-Bin Tang, Wen-Ya Li, Chi Wang, Lei Dai, Jin-Peng Han Chin. Phys. Lett.    2018, 35 (11): 119401 .   DOI: 10.1088/0256-307X/35/11/119401 Abstract   HTML   PDF (2772KB) At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves (KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90$^{\circ}$ pitch angle is observed throughout the flux rope, where intense KAWs are identified. The KAWs can effectively trap electrons by the wave parallel electric field and the magnetic mirror force, allowing electrons to undergo Landau resonance and be transported into more field-aligned directions. The pitch angle range for the trapped electrons is estimated from the wave analysis, which is in good agreement with direct pitch angle measurements of the electron distributions. The newly formed beam-like electron distribution is unstable and excites whistler waves, as revealed in the observations. We suggest that KAWs could be responsible for the plasma depletion inside a flux rope by this transport process, and thus be responsible for the formation of a typical flux rope.
 Select Global Statistical Study of Ionospheric Waves Based on COSMIC GPS Radio Occultation Data Xuan-Yun Zeng, Xiang-Hui Xue, Xin-An Yue, Ming-Jiao Jia, Bing-Kun Yu, Jian-Fei Wu, Chao Yu Chin. Phys. Lett.    2018, 35 (10): 109401 .   DOI: 10.1088/0256-307X/35/10/109401 Abstract   HTML   PDF (7182KB) Extracting and parameterizing ionospheric waves globally and statistically is a longstanding problem. Based on the multichannel maximum entropy method (MMEM) used for studying ionospheric waves by previous work, we calculate the parameters of ionospheric waves by applying the MMEM to numerously temporally approximate and spatially close global-positioning-system radio occultation total electron content profile triples provided by the unique clustered satellites flight between years 2006 and 2007 right after the constellation observing system for meteorology, ionosphere, and climate (COSMIC) mission launch. The results show that the amplitude of ionospheric waves increases at the low and high latitudes ($\sim$0.15 TECU) and decreases in the mid-latitudes ($\sim$0.05 TECU). The vertical wavelength of the ionospheric waves increases in the mid-latitudes (e.g., $\sim$50 km at altitudes of 200–250 km) and decreases at the low and high latitudes (e.g., $\sim$35 km at altitudes of 200–250 km). The horizontal wavelength shows a similar result (e.g., $\sim$1400 km in the mid-latitudes and $\sim$800 km at the low and high latitudes).
 Select Magnetic Field of a Compact Spherical Star under f(R,T) Gravity Safiqul Islam, Shantanu Basu Chin. Phys. Lett.    2018, 35 (9): 099501 .   DOI: 10.1088/0256-307X/35/9/099501 Abstract   HTML   PDF (624KB) We present the interior solutions of distributions of magnetized fluid inside a sphere in $f(R,T)$ gravity. The magnetized sphere is embedded in an exterior Reissner–Nordström metric. We assume that all physical quantities are in static equilibrium. The perfect fluid matter is studied under a particular form of the Lagrangian density $f(R,T)$. The magnetic field profile in modified gravity is calculated. Observational data of neutron stars are used to plot suitable models of magnetized compact objects. We reveal the effect of $f(R,T)$ gravity on the magnetic field profile, with application to neutron stars, especially highly magnetized neutron stars found in x-ray pulsar systems. Finally, the effective potential $V_{\rm eff}$ and innermost stable circular orbits, arising out of the motion of a test particle of negligible mass influenced by attraction or repulsion from the massive center, are discussed.
 Select Effect of Tidal Torques on Rotational Mixing in Close Binaries Zhi Li, Han-Feng Song, Wei-Guo Peng Chin. Phys. Lett.    2018, 35 (7): 079701 .   DOI: 10.1088/0256-307X/35/7/079701 Abstract   HTML   PDF (620KB) The effect of tidal torques on rotational mixing in close binaries is investigated. It is found that spin angular momentum can attain a high value due to a strong tidal torque. Nitrogen and helium enrichment occurs early in the binary system that is triggered by tides. The stellar radius can reach a high value in the single star model with high initial velocities at the early stage of the evolution, but efficient rotational mixing can inhibit stellar expanding at the subsequent evolution. Central compactness is increased by the centrifugal force at the early stage of evolution but is reduced by rotational mixing induced by strong tides. The binary models with weak tides have high values of central temperature and stellar radius. Rotational mixing in single stars can slow down the shrinkage of convective cores, while convective cores can be expanded by strong tides in the binary system. Efficient rotational mixing induced by tides can cause the star to evolve towards high temperature and luminosity.
 Select Simulation of the Galactic Cosmic Ray Shadow of the Sun Mohsin Saeed, Min Zha, Zhen Cao Chin. Phys. Lett.    2017, 34 (12): 129601 .   DOI: 10.1088/0256-307X/34/12/129601 Abstract   HTML   PDF (1559KB) The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space, and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise. A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth–Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.
 Select Constraints on Estimation of Radius of Double Pulsar PSR J0737-3039A and Its Neutron Star Nuclear Matter Composition Yi-Yan Yang, Li Chen, Rong-Feng Linghu, Li-Yun Zhang, Ali TAANI Chin. Phys. Lett.    2017, 34 (12): 129701 .   DOI: 10.1088/0256-307X/34/12/129701 Abstract   HTML   PDF (529KB) The aspect of formation and evolution of the recycled pulsar (PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram ($B$–$P$ diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate (or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.
 Select An Explanation for the Undetection of Radio Pulsar in Supernova 1987A Shuang-Qiang Wang, Na Wang, De-Hua Wang, Lun-Hua Shang Chin. Phys. Lett.    2017, 34 (12): 129702 .   DOI: 10.1088/0256-307X/34/12/129702 Abstract   HTML   PDF (520KB) Supernova 1987A is a core collapse supernova in the Large Magellanic Cloud, inside which the product is most likely a neutron star. Despite the most sensitive available detection instruments from radio to $\gamma$-ray wavebands being exploited in the pass thirty years, there have not yet been any pulse signals detected. By considering the density of the medium plasma in the remnant of 1987A, we find that the plasma cut-off frequency is approximately 7 GHz, a value higher than the conventional observational waveband of radio pulsars. As derived, with the expansion of the supernova remnant, the radio signal will be detected in 2073 A.D. at 3 GHz.
 Select Energy Conditions and Constraints on the Generalized Non-Local Gravity Model Ya-Bo Wu, Xue Zhang, Bo-Hai Chen, Nan Zhang, Meng-Meng Wu Chin. Phys. Lett.    2017, 34 (7): 079801 .   DOI: 10.1088/0256-307X/34/7/079801 Abstract   HTML   PDF (527KB) We study and derive the energy conditions in generalized non-local gravity, which is the modified theory of general relativity obtained by adding a term $m^{2n-2}R\Box^{-n}R$ to the Einstein–Hilbert action. Moreover, to obtain some insight on the meaning of the energy conditions, we illustrate the evolutions of four energy conditions with the model parameter $\varepsilon$ for different $n$. By analysis we give the constraints on the model parameters $\varepsilon$.
 Select Viscous Modified Chaplygin Gas in Classical and Loop Quantum Cosmology D. Aberkane, N. Mebarki, S. Benchikh Chin. Phys. Lett.    2017, 34 (6): 069801 .   DOI: 10.1088/0256-307X/34/6/069801 Abstract   HTML   PDF (664KB) We investigate the cosmological model of viscous modified Chaplygin gas (VMCG) in classical and loop quantum cosmology (LQC). Firstly, we constrain its equation of state parameters in the framework of standard cosmology from Union 2.1 SNe Ia data. Then, we probe the dynamical stability of this model in a universe filled with VMCG and baryonic fluid in LQC background. It is found that the model is very suitable with $(\chi^{2/d.o.f}=0.974)$ and gives a good prediction of the current values of the deceleration parameter $q_{0}=\in(-0.60,-0.57)$ and the effective state parameter $\omega_{\rm eff}\in(-0.76,-0.74)$ that is consistent with the recent observational data. The model can also predict the time crossing when $(\rho_{\rm DE}\approx\rho_{\rm matter})$ at $z=0.75$ and can solve the coincidence problem. In LQC background, the Big Bang singularity found in classical cosmology ceases to exist and is replaced by a bounce when the Hubble parameter vanishes at $\rho_{\rm tot}\approx \rho_{\rm c}$.
 Select Nucleosynthesis in Advection-Dominated Accretion Flow onto a Black Hole Jiang Zhang, Ren-Yi Ma, Hong-Jie Li, Bo Zhang Chin. Phys. Lett.    2017, 34 (4): 049701 .   DOI: 10.1088/0256-307X/34/4/049701 Abstract   HTML   PDF (3091KB) Nucleosynthesis in advection-dominated accretion flow (ADAF) onto a black hole is proposed to be an important role in chemical evolution around compact stars. We investigate the nucleosynthesis in ADAF relevant for a black hole of low mass, different from that of the self-similar solution. In particular, the presence of supersolar metal mass fractions of some isotopes seems to be associated with the known black hole nucleosynthesis in ADAF, which offers further evidence of diversity of the chemical enrichment.
 Select Effects of Tensor Couplings on Nucleonic Direct URCA Processes in Neutron Star Matter Yan Xu, Xiu-Lin Huang, Cheng-Zhi Liu, Tmurbagan Bao, Guang-Zhou Liu Chin. Phys. Lett.    2016, 33 (09): 099701 .   DOI: 10.1088/0256-307X/33/9/099701 Abstract   HTML   PDF (508KB) The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree–Fock approximation. We particularly study the influences of the tensor couplings of vector mesons $\omega$ and $\rho$ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons $\omega$ and $\rho$ can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons $\omega$ and $\rho$ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non-superfluid neutron star matter. However, when considering only the tensor coupling of vector meson $\rho$, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson $\rho$ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.
 Select The Pulsation Induced by Mass Transfer in Critically Rotating Stars Jiang-Tao Wang, Han-Feng Song Chin. Phys. Lett.    2016, 33 (09): 099702 .   DOI: 10.1088/0256-307X/33/9/099702 Abstract   HTML   PDF (516KB) The structural characteristics of the critically rotating accretor in binaries are investigated during rapid mass transfer. It is found that the accretor is subjected to periodic pulsation due to accretions and rejections of mass and angular momentum. The gainer attempts to attain both hydrostatic and thermal balances. This physical process can cause the thermal structure of the accreting star to fluctuate with a period of $\sim0.19$ y. Stellar wind can be enhanced by a factor of $\sim $$1.25$$\,\times\,$$10^{4}$ when the accretor approaches break-down velocity. Surface entropy and density decrease with the increase of the stellar radius due to the fact that rapid rotation leads to a reduction in the number density and surface temperature. The rotational energy has the same trend as stellar radius due to stellar expansion. Surface opacity which is extremely sensitive to surface temperature has an opposite trend to stellar radius. Moreover, the rate of nuclear energy must be adjusted due to mass removal or accretion at the stellar surface.
 Select A Possible Cause of Magnetic Anomalies on the Southern Martian Hemisphere Chu-Xin Chen Chin. Phys. Lett.    2016, 33 (08): 089601 .   DOI: 10.1088/0256-307X/33/8/089601 Abstract   HTML   PDF (247KB) From the topology of a synthetic aurora map, we propose a mechanism for the magnetic anomalies on the southern martian hemisphere, i.e., impacts by asteroids when the dynamo is active. The quasi concentric circles of aurora suggest that there are two-to-three convectional cells for each impact. The whole synthetic aurora is induced by three major impacts of asteroids. The east–west lineation features of crust magnetizations are due to the east–west trending locations of three impacts. The alternatively changed sign of crust magnetization originates from the alternatively changed flow direction on the tops of adjacent convectional cells.
 Select Cosmic Constraints to the $w$CDM Model from Strong Gravitational Lensing Jie An, Bao-Rong Chang, Li-Xin Xu Chin. Phys. Lett.    2016, 33 (07): 079801 .   DOI: 10.1088/0256-307X/33/7/079801 Abstract   HTML   PDF (1075KB) We study the cosmic constraint to the $w$CDM (cold dark matter with a constant equation of state $w$) model via 118 strong gravitational lensing systems which are compiled from SLACS, BELLS, LSD and SL2S surveys, where the ratio between two angular diameter distances $D^{\rm obs}=D_{\rm A}(z_{\rm l},z_{\rm s})/D_{\rm A}(0,z_{\rm s})$ is taken as a cosmic observable. To obtain this ratio, we adopt two strong lensing models: one is the singular isothermal sphere model (SIS) and the other one is the power-law density profile (PLP) model. Via the Markov chain Monte Carlo method, the posterior distribution of the cosmological model parameters space is obtained. The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index $\gamma$. Furthermore, the PLP model gives a relatively tighter constraint to the cosmological parameters than that of the SIS model. The predicted value of ${\it \Omega}_{\rm m}=0.31^{+0.44}_{-0.24}$ by the SIS model is compatible with that obtained by Planck2015: ${\it \Omega}_{\rm m}=0.313\pm0.013$. However, the value of ${\it \Omega}_{\rm m}=0.15^{+0.13}_{-0.11}$ based on the PLP model is smaller and has $1.25\sigma$ tension with that obtained by Planck2015.
 Select Dynamical Study of a Constant Viscous Dark Energy Model in Classical and Loop Quantum Cosmology Sara Benchikh, Noureddine Mebarki, Dalel Aberkane Chin. Phys. Lett.    2016, 33 (05): 059501 .   DOI: 10.1088/0256-307X/33/5/059501 Abstract   HTML   PDF (679KB) Dynamical behaviors and stability properties of a flat space Friedmann–Robertson–Walker universe filled with pressureless dark matter and viscous dark energy are studied in the context of standard classical and loop quantum cosmology. Assuming that the dark energy has a constant bulk viscosity, it is found that the bulk viscosity effects influence only the quintessence model case leading to the existence of a viscous late time attractor solution of de-Sitter type, whereas the quantum geometry effects influence the phantom model case where the big rip singularity is removed. Moreover, our results of the Hubble parameter as a function of the redshift are in good agreement with the more recent data.
 Select Test of the Cosmic Transparency with the Baryon Acoustic Oscillation and Type Ia Supernova Data He-Kun Li, Pu-Xun Wu, Hong-Wei Yu Chin. Phys. Lett.    2016, 33 (05): 059801 .   DOI: 10.1088/0256-307X/33/5/059801 Abstract   HTML   PDF (375KB) We use the latest baryon acoustic oscillation and Union 2.1 type Ia supernova data to test the cosmic opacity between different redshift regions without assuming any cosmological models. It is found that the universe may be opaque between the redshift regions 0.35–0.44, 0.44–0.57 and 0.6–0.73 since the best fit values of cosmic opacity in these regions are positive, while a transparent universe is favored in the redshift region 0.57–0.63. However, in general, a transparent universe is still consistent with observations at the $1\sigma$ confidence level.
 Select Consistency Conditions and Constraints on Generalized $f(R)$ Gravity with Arbitrary Geometry-Matter Coupling Si-Yu Wu, Ya-Bo Wu, Yue-Yue Zhao, Xue Zhang, Cheng-Yuan Zhang, Bo-Hai Chen Chin. Phys. Lett.    2016, 33 (03): 039801 .   DOI: 10.1088/0256-307X/33/3/039801 Abstract   HTML   PDF (533KB) We study the consistency conditions of the generalized $f(R)$ gravity by extending $f(R)$ gravity with non-minimal coupling to the generalized $f(R)$ with arbitrary geometry-matter coupling. Specifically, we discuss the two particular models of generalized $f(R)$ by means of consistency conditions. It is found that the second model is not physically viable so as to be ruled out. Moreover, we further constrain the first model using the Dolgov–Kawasaki stability criterion, and give the value ranges of the parameters in the first model. It is worth stressing that our results include the ones in $f(R)$ gravity with non-minimal coupling as the special case of $Q(L_{\rm m})=L_{\rm m}$.
 Select Quintessence Cosmology with an Effective Λ-Term in Lyra Manifold Khurshudyan M., Pasqua A., Sadeghi J., Farahani H. Chin. Phys. Lett.    2015, 32 (10): 109501 .   DOI: 10.1088/0256-307X/32/10/109501 Abstract   PDF (491KB) We study quintessence cosmology with an effective Λ-term in Lyra manifold. We consider three different models by choosing variable Λ depending on time, the Hubble parameter and the energy density of dark matter and dark energy. Dark energy is assumed as quintessence which interacts with the dark matter. Using numerical analysis we investigate the behavior of cosmological parameters in three different models and compare our results with observational data. State-finder diagnostic is also performed for all models.
 Select Glitch Crisis or Not: a Microscopic Study LI Ang Chin. Phys. Lett.    2015, 32 (07): 079701 .   DOI: 10.1088/0256-307X/32/7/079701 Abstract   PDF (402KB) The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two-component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However, the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4 M? canonical star, based on a microscopic equation of state for the neutron star's core using the Brueckner–Hartree–Fock approach. For this purpose, two requisite parameters are chosen as follows: the core-crust transition pressure is in the range of Pt=0.2–0.65 MeV/fm3, and the fractional crust radius ΔR/R=0.082 based on experiments. To account for the possibility of a heavier star, a larger value of ΔR/R=0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.
 Select Constraining the Generalized and Superfluid Chaplygin Gas Models with the Sandage–Loeb Test ZHU Wen-Tao, WU Pu-Xun, YU Hong-Wei Chin. Phys. Lett.    2015, 32 (5): 059501 .   DOI: 10.1088/0256-307X/32/5/059501 Abstract   PDF (1138KB) The Sandage–Loeb (SL) test is a direct measurement of the cosmic expansion by probing the redshift drifts of quasi-stellar objects in the 'redshift desert' of 2
 Select Effects of Gravitational Correction on Neutrino Emission from Neutron Stars DING Wen-Bo, E Shan-Shan, YU Zi, ZHANG Qi, QI Zhan-Qiang Chin. Phys. Lett.    2015, 32 (5): 059701 .   DOI: 10.1088/0256-307X/32/5/059701 Abstract   PDF (598KB) Considering the gravitational correction through introduction of weakly interacting light vector U bosons, not only the equation of state (EoS) of the neutron star matter, but also the cooling properties of neutron stars may be changed. In this work, effects of gravitational correction on neutrino emission and cooling of neutron stars in the matter with neutrons, protons, electrons, muons, Δ? and Δ0 are studied by the relativistic mean field theory and the related cooling theory. The results show that the effects are sensitive to the ratio of coupling strength to mass squared of U bosons, defined as gU. With increasing gU, the radial region where direct Urca process of nucleons can be allowed in a neutron star with the fixed mass becomes narrower, while the neutrino emissivity is somewhat higher. Moreover, the gravitational correction suppresses the effects of Δ? on neutrino emission. The gravitational correction leads the star to cool faster, and the higher the gU is, the faster the star cools.
 Select Constraining Equation of State of Dark Matter: Including Weak Gravitational Lensing YANG Lei, YANG Wei-Qiang, XU Li-Xin Chin. Phys. Lett.    2015, 32 (5): 059801 .   DOI: 10.1088/0256-307X/32/5/059801 Abstract   PDF (517KB) Usually the equation of state (EoS) of dark matter is zero when it is cold, however there exists the possibility of a (effective) nonzero EoS of dark matter due to its decay and interaction with dark energy. In this work, we try to constrain the EoS of dark matter wdm using the currently available cosmic observations which include the geometrical and dynamical measurements. For the geometrical measurements, the luminosity distance of type Ia supernovae, the angular diameter distance and comoving sound horizon from baryon acoustic oscillations and the cosmic microwave background radiation will be employed. The data points from the redshift-space distortion and weak gravitational lensing will be taken as dynamical measurements. Using the Markov chain Monte Carlo method, we obtain a very tight constraint on the EoS of dark matter: wdm=0.0000532?0.000686?0.00136?0.00177+0.000692+0.00136+0.00183.
 Select Energy Extraction from a Black Hole and Its Influence on X-Ray Spectra HUANG Chang-Yin, GONG Xiao-Long, WANG Ding-Xiong Chin. Phys. Lett.    2014, 31 (12): 129701 .   DOI: 10.1088/0256-307X/31/12/129701 Abstract   PDF (561KB) Taking into account the energy and angular momentum transferred from a rotating black hole (BH) to the inner accretion disk by the magnetic connection (MC) process, we simulate the x-ray spectra from the disk-corona system with two different magnetic configurations using the Monte Carlo method. The results show that the MC process reduces the ratio of the power dissipated in the corona to the total and softens the spectrum. The influence of the MC process is stronger with a higher BH spin, a larger accretion rate, and a larger and more centralized magnetic flux threading the disk. The comparison of the model spectra with the observational data suggests that large-scale magnetic fields accumulating in the inner disk could be a candidate explanation for the hard-to-soft state evolutions in BH binaries.
 Select Characteristics of Double Gamma-Ray Bursts LIU Tong, SUN Mou-Yuan, HOU Shu-Jin, LI Ang, ZHANG Fu-Wen, GU Wei-Min, LU Ju-Fu Chin. Phys. Lett.    2014, 31 (11): 119801 .   DOI: 10.1088/0256-307X/31/11/119801 Abstract   PDF (557KB) Double gamma-ray bursts (DGRBs) have two well-separated sub-bursts in the main prompt emission and the typical time interval between them is in the hundreds of seconds. Among DGRBs, gamma-ray bursts (DGRBs) 110801A and 120716A are the ones with known redshifts. However, unlike GRB 110801A, we show that the two sub-bursts of GRB 120716A is severally similar to the short- and long-duration GRBs, thus it is difficult to explain the origin of GRB 120716A by the popular models on the central engine of GRBs. We suggest that some mechanisms of x-ray flares in GRBs, i.e., a post-merger millisecond pulsars or the jet precession in a black hole hyperaccretion system may produce the DGRB.
 Select Hadronic Scenarios for Gamma-Ray Emission from Three Supernova Remnants Interacting with Molecular Clouds YU Huan, FANG Jun, ZHANG Li Chin. Phys. Lett.    2014, 31 (04): 049801 .   DOI: 10.1088/0256-307X/31/4/049801 Abstract   PDF (546KB) GeV γ-rays detected with the large area telescope on board the Fermi Gamma-ray space telescope in the direction of HB21, MSH 17-39 and G337.0-0.1 have been recently reported. The three supernova remnants (SNRs) show interactions with molecular clouds, and they are effective gamma-ray emitters as the relativistic protons accelerated by the SNR shocks inelastically colliding with the dense gas in the clouds. The origin of the observed γ-rays for the three remnants is investigated in the scenario of the diffusive shock acceleration. In the model, a part of the SNR shock transmits into the nearby molecular clouds, and the shock velocity is greatly reduced. As a result, a shock with a relatively low Alfvén Mach number is generated, and the spectra of the accelerated protons and theγ-ray photons produced via proton-proton interaction can be obtained. The results show that the observed γ-ray spectra for the three SNRs interacting with the molecular clouds can be reproduced. It can be concluded that the hadronic origin of the γ-rays for the three SNRs is approved, and the ability of SNR shocks to accelerate protons is also supported.
 Select An Improved Model of the Jovian Magnetosphere LU Bin, CHEN Chu-Xin Chin. Phys. Lett.    2014, 31 (03): 039601 .   DOI: 10.1088/0256-307X/31/3/039601 Abstract   PDF (436KB) The Jovian magnetosphere is modulated by the solar wind and centrifugal force. The configuration of the magnetic field in the previous model of the magnetosphere including the centrifugal force is consistent with the observations at low magnetic latitude (Λ<50°), while there is a substantial difference between the results of the model and the observations at high magnetic latitude (Λ≥50°), especially in the distant magnetotail. Based on the previous model, a new configuration of the Jovian magnetosphere in the night side is suggested by a three-step transformation in this study. The new magnetosphere obtained by the transformation method is flattened in the z-direction and stretched in the x-direction in distant magnetotail, which agree with general knowledge.
 Select Reconstruction of New Holographic Chaplygin Gas Model with Viscosity WU Ya-Bo, TONG Hai-Dan, YANG Hao, LU Jian-Bo, ZHAO Yue-Yue, LU Jun-Wang, ZHANG Xue Chin. Phys. Lett.    2014, 31 (2): 029801 .   DOI: 10.1088/0256-307X/31/2/029801 Abstract   PDF (530KB) We investigate the interacting new holographic dark energy (HDE) with viscosity. Specifically, we not only study the dynamical evolutions of the new HDE with viscosity and the influences of viscosity as well as the coupling constant on the equation of state for the new HDE, but also establish the correspondence between the new HDE with viscosity and variable generalized Chaplygin gas (VGCG) models in the flat Friedmann–Robertson–Walker universe. Furthermore, we also reconstruct the potential and the dynamics of VGCG as the scalar field. By analysis we show that for the new holographic Chaplygin gas model, if the related parameters to the potential satisfy some constraints, the accelerated expansion can be achieved. These research results can reduce to the ones without viscosity.
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