Strange stars properties calculated in the framework of the Field Correlator Method

We calculate the strange star properties in the framework of the Field Correlator Method. We find that for gluon condensate values G₂$G_2$ in the range 0.006–0.007 GeV⁴$0.006\text{–}0.007{\text{GeV}}^4$, which give a critical temperature Tc∼170 MeV$T_c\sim 170\text{MeV}$ at μc=0${\mu }_c=0$, the sequences of strange stars are compatible with some of the semi-empirical mass–radius relations and data obtained from astrophysical observations.     

Extraction of Nuclear Matter Properties from Nuclear Masses by a Model of Equation of State

The extraction of nuclear matter properties from measured nuclear masses is investigated in the energy density functional formalism of nuclei.It is shown that the volume energy a1 and the nuclear incompressibility Ko depend essentially on μ_nN + μ_pZ - 2E_N,whereas the symmetry energy J and the density symmetry coefficient L as well as symmetry incompressibility Ks depend essentially on μ_n - μ_p,where μ_p ＝μp - ∂E_c/∂Z,μ_n and μ_p are the neutron and proton chemical potentials respectively,E_N the nuclear energy,and E_c the Coulomb energy.The obtained symmetry energy is J ＝ 28.5 MeV,while other coefficients are uncertain within ranges depending on the model of nuclear equation of state.     

On some measurements of the propagation properties of thermal waves in the Nb-H and Ta-H systems

Summary By means of an experimental technique based on a nonsteady-state method,i.e. on the propagation of thermal waves, we have measured at room temperature for oscillation frequencies between 6 and 30 mHz the thermal diffusivity, the lateral thermal-loss coefficient and the ?fractional heat loss? in Nb and Ta wires as a function of hydrogen doping. The appearance of hydride formation and precipitation notably changes the behaviour of these quantities. From these measurements it was also possible to calculate the propagation velocity and attenuation coefficient of thermal waves. It was found that the increase of the hydrogen concentration in the solid solution produces a gradual decrease in the velocity and increase in the attenuation coefficient until the solubility limit is reached. For larger hydrogen concentrations, the velocity showed a tendency to increase towards the value of the pure metal, while the attenuation coefficient decreased below the value of the pure metal. These results as a whole appear quite promising for studying the properties of hydrogenated systems. This work was supported by the Gruppo Nazionale di Struttura della Materia of the Consiglio Nazionale delle Ricerche and by the Centro Interuniversitario di Struttura della Materia of the M.P.I., Roma (Italia).     

暗物质理论研究进展

评述了天体物理中暗物质的发现以及标准模型所面临的问题,综述了解决这些问题及标准模型之外可能出现的新物理与暗物质的联系。介绍了暗物质粒子选择条件和可能的暗物质粒子的候选者;对圆柱形暗物质表面密度与星系和星系团暗物质晕的晕核半径的关系进行了讨论,与其他模型进行了比较,得出暗物质晕的特征半径r_*的暗物质表面密度分布不是一个普适量;并叙述了近几年暗物质研究中提出的新理论模型-Hidden dark matter,最后叙述了中国暗物质实验探测研究的进展,2016年底DAMPE的第一批数据有可能给出;中国锦屏地下实验室（CJPL）的CDEX和PandaX合作组的第一期实验没有发现暗物质粒子存在的信号,期待他们下期的实验。A review of the evidence of the dark matter found in universe and the problems faced by the standard model. To address these issues as well as the possible relationship between the new physics beyond the standard model and dark matter, and given the selection condition of dark matter and possible candidates of the weakly-interacting massive particles (WIMPs). The correlation between the column surface density and the halo core radius of the dark matter halos of galaxies and cluster of galaxies is discussed, and the other models are compared. We find that the surface density within the halo characteristic radius r* is not an universal quantity; The new model (hidden dark matter)proposed in the study of dark matter is described. At last, the research progress of dark matter experiment in China is commented. At the end of 2016, the first batch of DAMPE data may be given;No significant excess events of WIMPS were found in the first stage of both the CDEX and PandaX experiments located in the China Jinping Underground Laboratory(CJPL). Look forward to their the next stage of these experiments in CJPL.     

Geometric Conditions on the Type of Matter Determining the Flat Behavior of the Rotational Curves in Galaxies

In an arbitrary axisymmetric stationary spacetime, we determine the expression for the tangential velocity of test objects following a circular stable geodesic motion in the equatorial plane, as function of the metric coefficients. Next, we impose the condition, observed in large samples of disks galaxies, that the magnitude of such tangential velocity be radii independent in the dark matter dominated region, obtaining a constraint equation among the metric coefficients, and thus arriving to an iff (iff means: if and only if.) condition: The tangential velocity of test particles is radii independent iff the metric coefficients satisfied the mentioned constraint equation. Furthermore, for the static case, the constraint equation can be easily integrated, leaving the spacetime at the equatorial plane essentially with only one independent metric coefficient. With the geometry thus fixed, we compute the Einstein tensor and equate it to an arbitrary stress energy tensor, in order to determine the type of energy-matter which could produce such a geometry. Within an approximation, we deduce a constraint equation among the components of the stress energy tensor. We test in that constraint equation several well known types of matter, which have been proposed as dark matter candidates and are able to point for possible right ones. Finally, we also present the spherically symmetric static case and apply the mentioned procedure to perfect fluid stress energy tensor, recovering the Newtonian result as well as the one obtained in the axisymmetric case. We also present arguments on the need to use GR to study types of matter different than the dust one.     

The effect of the chemical environment on theKβ/Kα X-ray intensity ratio

Summary Chemical effects on theKβ/Kα X-ray intensity ratios were investigated for different constitutions of Ti, V, Fe, Se, Br, Zr and Ce by a Ge(Li) X-ray detector. The vacancies were produced by heavily filtered²⁴¹Am gamma-rays. It is found that theKβ/Kα X-ray intensity ratios measured with compounds deviated up to 12% from the corresponding values of the pure elements (Ti, V, Fe) are larger than for the others (Se, Br, Zr and Ce).     

凝聚态物质状态方程的一个数值模型

建立了凝聚态物质的一个三项式状态方程：以Faussurier平均原子模型为基础计算电子热压和电子热能;以Cowan模型为基础计算离子热压和离子热能;用基于实验数据的半经验拟合公式计算物质的冷压和冷能。用实验数据检验了用平均原子模型计算的平均电离度。将状态方程与Hugoniot关系式相结合,计算了Be和Al的冲击绝热曲线,结果充分地展现出电子在高温、高密度条件下的壳层结构效应。     

N Law for bosons in 2D

A rigorous upper bound is derived for the exact ground-state energy of N negative charged bosons and N motionless, i.e. fixed, positive charges with Coulomb interactions in 2D for arbitrary N ? 4 giving rise to an N²-upper bound. The consistency of such an N² behaviour is also investigated by examining a lower bound to the ground-state energy.     

A ring-source method to measure the thermal diffusivity of a conducting specimen in forced air flow: Study on aluminium

Summary Thermal diffusivity is obtained with an accuracy of ∼ 1% by means of a new simple method, in which two parallel disks (of chromel and alumel, respectively) surround the middle section of a cylindrical specimen of conducting material. The disks act in the clamped zone as the hot juction of a thermocouple and, at the same time, as a heat source for the specimen, subjected to a laminar air flow. A second thermocouple placed at the base of the cylinder accomplishes acquisition of another set of experimental data from which the thermal diffusivity and the surface heat loss coefficient can be determined. Preliminary measurements on aluminium 99.999% consistent with literature data have been reported. Work supported by the Ministero della Pubblica Istruzione of the Italian Goverment.     

Stability and instability of relativistic electrons in classical electromagnetic fields

The stability of matter composed of electrons and static nuclei is investigated for a relativistic dynamics for the electrons given by a suitably projected Dirac operator and with Coulomb interactions. In addition there is an arbitrary classical magnetic field of finite energy. Despite the previously known facts that ordinary nonrelativistic matter with magnetic fields, or relativistic matter without magnetic fields, is already unstable when a, the fine structure constant, is too large, it is noteworthy that the combination of the two is still stableprovided the projection onto the positive energy states of the Dirac operator, whichdefines the electron, is chosen properly. A good choice is to include the magnetic field in the definition. A bad choice, which always leads to instability, is the usual one in which the positive energy states are defined by the free Dirac operator. Both assertions are proved here. This paper is dedicated to Bernard Jancovici on the occasion of his 65th birthday.     

Effect of granular size on the angle of repose in the chute

Avalanche in the chute has been studied to examine how the sizes of granules affect the angle of repose θ _r when the width of the chute is fixed. The results show that the angle of repose in the chute has exponential decay with λ, which is the reciprocal of granular diameter d. The fluctuation of the angle of repose is also studied during the chute being tilted, and the results indicate that the fluctuation of the angle of repose increases with the increase of granular diameter d. Supported by the Youth Project Foundation of Taizhou University (Grant No. 06QN08)     

Heterotic string dark matter from the graviton multiplet

In the string theory framework for physics beyond the standard model the hidden sector of E₈×E₈ heterotic string theory and the graviton multiplet provide compelling sources for the dark matter in the universe.

In the present investigation I consider the graviton multiplet as one particular dark matter source in heterotic string theory. In particular, it is pointed out that an appreciable fraction of dark matter from the graviton multiplet requires a mass generating phase transition around T_c10⁸ GeV, where the symmetry partners of the graviton would evolve from an ultrahard fluid to pressureless dark matter. This indicates m10 MeV for the massive components of the graviton multiplet, and it is reassuring that the corresponding dilaton lifetime τ10¹⁷ s is compatible with a dark matter interpretation.     

颗粒介质的离散态特性研究

回顾了颗粒介质中应力的分布和传播模式以及物体在颗粒介质中运动所受阻力的研究进展，并报道了我们对颗粒体系中代表离散特性的颗粒尺寸效应对颗粒介质特性影响的研究.研究发现物体由于自身重量在颗粒介质中下沉的深度随着颗粒尺寸的增大单调减小；球体在下陷过程中受到的颗粒床的支撑力，除了在约1 mm范围的表面作用区域以外，与下陷深度之间满足很好的幂率关系，幂值在1.5—1.0之间，并且此幂值随着颗粒尺寸的增大而单调减小.颗粒床的支撑力与下陷深度的幂率关系可解释为颗粒介质内部应力结构重组的宏观反应结果. 关键词： 颗粒物质 离散介质力学     

Study of the glass transition region in amorphous selenium by EXAFS

Summary EXAFS spectra of amorphous bulk selenium and Se₈₀Te₂₀ alloy have been analysed in the temperature range of the glass transition region (−15 to 37°C). α-Se shows an unexpected behaviour because the modulated part of the X absorption increases with the temperature, irrespectively of the action of the EXAFS Debye-Waller factor from which one expects an opposite behaviour. Analogous features do not appear in the Se₈₀Te₂₀ alloy, probably because of the role played by the intramolecular covalent Se−Te bond strength, weaker than the corresponding Se−Se. In the absence of suitable models for the temperature dependence of the microscopic processes occurring in glasses nearT _g, a tentative explanation is proposed in terms of the temperature dependence of the backscattering amplitude functionF(k).

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Riassunto Il selenio amorfo e lega Se₈₀Te₂₀ sono stati studiati con tecnica EXAFS nell'intervallo delle temperature noto come regione della transizione vetrosaT _g (da −15 a 37°C). Il selenio amorfo mostra un comportamento inaspettato per effetto dell'aumento, con la temperatura sottoT _g, della parte modulata dell'assorbimento dei raggi X, in contrasto con quanto ci si aspetterebbe per l'effetto di smorzamento del fattore di Debye-Waller. Un comportamento analogo non si riscontra invece nella lega Se₈₀Te₂₀ dove, probabilmente, il legame covalente intracatena Se−Te, piú debole del corrispondente Se−Se, rende piú efficace l'azione di smorzamento del fattore di Debye-Waller, smascherando altri effetti. In assenza di modelli adeguati che descrivono la dipendenza dalla temperatura dei processi microscopici nei materiali vetrosi nella regione della transizione vetrosa, si ipotizza che il comportamento ≪anomalo≫ del selenio sia attribuibile ad una dipendenza dalla temperatura della funzione ampiezza di backscatteringF(k).

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Резюме Анализируются спектры EXAFS аморфного объемного селена и сплава Se₈₀Te₂₀ в области температур переходной области стекла (от 15° до 37°C). а-Se обнаруживает неожиданное поведение, потому что модулированная часть Х поглощения увеличивается с температурой, независимо от действия фактора дебая-Уоллера EXAFS, который предполагает противоположное поведение. Аналогичные особенности не возникают в сплаве Se₈₀Te₂₀, так как сила межмолекулярной ковалентной связи Se−Te, по-видимому, слабее, чем соответствующвя связь Se−Se. В отсутствии соответствующих моделей для температурной зависимости микроскопических процессов, происходящих в стеклах вблизиT _g,a, предлагается предварительное объяснение в терминах температурной зависимости функцииF(k) амплитуды обратного рассеяния.

     

Hamiltonian formulation for the positron trapping model

Summary A Hamiltonian formulation is used to build up an adequate Hamiltonian for the positron trapping model. The number of positrons annihilated in the free state,n _f, or the trapped one,n _v, are considered canonical conjugate variables; this point of view provides a route to propose a Hamiltonian which leads to the previously proposed phenomenological master equations.

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Riassunto Si usa una formulazione hamiltoniana per elaborare un'hamiltoniana adeguata per il modello a trappola dei positroni. Il numero di positroni annichilati nello stato libero,n _f, o in quello intrappolato,n _v, è considerato come variabili coniugate canoniche; in questo senso si fornisce una via per proporre un'hamiltoniana che porti alle equazioni principali fenomenologiche proposte precedentemente.

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Резюме Гамильтонова формулировка используется для конструирования адекватного Гамильтониана для модели захвата позитрона. Число аннигилированных позитронов в свободном состоянии,n _f, или число захваченных позитронов,n _v, рассматриваются как канонически сопряженные переменные. Этот подход приводит к Гамильтониану. Который дает ранее предположенные феноменологические ?управляющие? уравнения.

     

通道宽度对二维粗糙边界斜面颗粒流的影响

在此之前已经报道了二维斜面颗粒流在通道中的分布规律以及二维斜面粗糙边界附近的颗粒 流量密度（ξ=ρ·ν）分布.本文则主要研究通道宽度W对边界附近颗粒流量密度(ξ=ρ· ν)分布的影响.结果表明，颗粒流量密度随通道宽度的变化（ξ W）存在一临界通道宽度W c.在本实验条件下临界通道宽度Wc=70d.当通道宽度小于临界宽度Wc时 ，通道中距边界20d—30d区间内的相对颗粒流量密度随斜面倾斜角的变化可描述为ξ∝( sinθ)α，α是与通道宽度W有关的参数，其数值在032至085之间. 关键词： 二维颗粒流 颗粒物质 颗粒流量密度     

暗物质粒子的质量与物态

讨论一类与宇宙超大尺度结构有关的、稳定的弱作用暗物质粒子,它们很可能是处在简并态的费米子(也可能处在近高温态)和处在近高温态的玻色子,其质量均为～10^－1eV,而其化学势的绝对值均远小于10^－1eV,这个结果与超高能原初宇宙线能谱在～10¹⁵eV及～10¹⁸eV附近出现拐折的现象不相矛盾.     

Neutron stars within the SU(2) parity doublet model

The equation of state of beta-stable and charge neutral nucleonic matter is computed within theSU(2) parity doublet model in mean-field and in the relativistic Hartree approximation. The mass of the chiral partner of the nucleon is assumed to be 1200MeV. The transition to the chiral restored phase turns out to be a smooth crossover in all the cases considered, taking place at a baryon density of just 2ρ₀ . The mass-radius relations of compact stars are calculated to constrain the model parameters from the maximum mass limit of neutron stars. It is demonstrated that chiral symmetry starts to be restored, which in this model implies the appearance of the chiral partners of the nucleons, in the center of neutron stars. However, the analysis of the decay width of the assumed chiral partner of the nucleon poses limits on the validity of the present version of the model to describe vacuum properties.     

An upper bound on the critical temperature for a continuous system with short-range interaction

A classical gas with short-range interaction in the grand canonical ensemble is studied. Ifp(, z) denotes the thermodynamic pressure at inverse temperature and activityz, then it follows from the Mayer expansion thatp(, z) is infinitely differentiable provided andz are sufficiently small. Here it is shown that there exists ₀>0 such thatp(, z) is infinitely differentiable if< ₀ andz>0. One can interpret this result as saying that ( ₀)^–1 is an upper bound on the critical temperature for the system.