The Main Path to C, N, O Elements in Big Bang Nucleosynthesis

The production of C, N, O elements in a standard big bang nucleosynthesis scenario is investigated. Using the up-to-date data of nuclear reactions in BBN, in particular the ^8Li （n,γ） ^9Li which has been measured in China Institute of Atomic Energy, a full nucleosynthesis network calculation of BBN is carried out. Our calculation results show that the abundance of 12 C is increased for an order of magnitude after addition of the reaction chain ^8Li（n,γ） ^9Li（α,n） ^12B（β） ^12C, which was neglected in previous studies. We find that this sequence provides the main channel to convert the light elements into C, N, O in standard BBN.     

超越爱因斯坦,从大爆炸到黑洞

据美国双月刊《Mercury》报道：由众多宇宙学家、理论工作者和天体物理学家在2004年5月12～15日于美国斯坦福大学校园举行的学术会议讨论了黑洞、暗能量、暗物质、空间的额外维数和弦论等问题．     

Letter: Effects of a Torsion Field on Big Bang Nucleosynthesis

In this paper we investigate whether torsion,which arises naturally in most theories of quantumgravity, has observable implications for the Big Bangnucleosynthesis. Torsion can lead to spin flips amongst neutrinos thus turning them into sterileneutrinos. In the early Universe they can alter thehelium abundance which is tightly constrained byobservations. Here I calculate to what extent torsion ofthe string theory type leads to a disagreement withthe Big Bang nucleosynthesis predictions.     

在RHIC和LHC能区双喷注诱发的马赫锥：大爆炸物质的声速

A study of Mach shocks generated by fast partonic jets propagating through the quark-gluon plasma (QGP) is reviewed briefly. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies compared to those created by a jet propagation through a static medium. Moreover, a new hydrodynamical study of jet energy loss is presented.     

在RHIC和LHC能区双喷注诱发的马赫锥:大爆炸物质的声速

A study of Mach shocks generated by fast partonic jets propagating through the quark-gluon plasma(QGP)is reviewed briefly.We predict a significant deformation of Mach shocks in central Au Au collisions at RHIC and LHC energies compared to those created by a jet propagation through a static medium. Moreover,a new hydrodynamical study of jet energy loss is presented.     

大爆炸核合成相关的8Li(d,p)9Li反应截面测量

利用8Li次级束测量了质心系能量7.8 MeV2H(8Li, 9Li)1H反应的角分布，导出了8Li(d, p)9Li反应的天体物理S因子及9Li→8Li+n虚衰变的渐近归一化系数. We have measured the angular distribution of 2H(8Li,9Li)1H at Ecm= 7.8 MeV and deduced the astrophysical S factor of 8Li(d, p)9Li reaction as well as the Asymptotic Normalization Coefficient (ANC) for 9Li → 8Li+n virtual decay.     

Big entropy fluctuations in statistical equilibrium: The macroscopic kinetics

Large entropy fluctuations in the equilibrium steady state of classical mechanics are studied in extensive numerical experiments in a simple strongly chaotic Hamiltonian model with two degrees of freedom described by the modified Arnold cat map. The rise and fall of a large separated fluctuation is shown to be described by the (regular and stable) “macroscopic” kinetics, both fast (ballistic) and slow (diffusive). We abandon a vague problem of the “appropriate” initial conditions by observing (in a long run) a spontaneous birth and death of arbitrarily big fluctuations for any initial state of our dynamical model. Statistics of the infinite chain of fluctuations similar to the Poincaré recurrences is shown to be Poissonian. A simple empirical relationship for the mean period between the fluctuations (the Poincaré “cycle”) is found and confirmed in numerical experiments. We propose a new representation of the entropy via the variance of only a few trajectories (“particles”) that greatly facilitates the computation and at the same time is sufficiently accurate for big fluctuations. The relation of our results to long-standing debates over the statistical “irreversibility” and the “time arrow” is briefly discussed.     

The single-fibre pull-out method: its advantages,interpretation and experimental realization

Past results from the single-fibre pull-out tests are reviewed and new results obtained with carbon in thermoplastics are presented. The force-distance curve during pull-out indicates some pseudo-ductility, in some cases, as the applied force builds up to the failure load. However, the failure itself is not ductile; rather, it is sudden, suggesting brittle fracture. The debonding force vs. embedded length (L) plots range from straight lines intersecting the origin, through smooth curves, to scatter diagrams, depending on the fibre and polymer. Interfacial shear strengths estimated from the shorter embedded lengths are often high and, quite frequently, higher than that of the polymer matrix. In addition, there is normally no correlation between interface properties (strength or work of fracture) and the corresponding polymer properties. This could well be due to the growth of an oriented interphasial layer, with a modulus and strength up to six times greater than that of the bulk polymer, as has been observed for modulus at least, with particulate reinforced materials.     

The water molecule and its interactions: the interaction between theory, modelling, and experiment

Understanding the behaviour of water at the molecular level requires a quantitative understanding of the water molecule and its interactions. Although many current empirical potential functions are able to reproduce some of the known behaviour, our understanding of the water molecule and its interactions is not yet sufficient for our modelling to reproduce much of the subtleness of the water molecule's behaviour in both the pure liquid and in solution. Some recent experimental and theoretical developments are discussed that may lead to an improvement in our understanding of the water molecule and its interactions in a range of environments and over a range of experimental conditions.     

Big q-Jacobi polynomials,q-Hahn polynomials,and a family of quantum 3-spheres

The big q-Jacobi polynomials and the q-Hahn polynomials are realized as spherical functions on a new quantum SU _q (2)-space which can be regarded as the total space of a family of quantum 3-spheres.     

Engineering the Big Chill: The Story of JLab’s Central Helium Liquefier

This article tells the story of the Central Helium Liquefier (CHL) at the Thomas Jefferson National Accelerator Facility (JLab), one of the US National Laboratories. JLab’s successful superconducting radio frequency accelerator was only possible because a group of JLab engineers successfully tackled a complex of difficulties to build a cryogenic system that included the CHL, a task that required advancing the frontier of cryogenic technology. Ultimately, these cryogenic advances were applied far beyond JLab to the benefit of cutting-edge programs at other US national laboratories (Oak Ridge, Brookhaven, and the Facility for Rare Isotope Beams at MSU) as well as NASA. This innovation story dramatizes the sort of engineer-driven technological problem solving that allows the successful launch and operation of experimental projects. Along the way, the CHL story also provides an important addition to our understanding of the role played by engineers and industry in creating knowledge at physics laboratories.     

Nonadditive entropy: The concept and its use

The thermodynamical concept of entropy was introduced by Clausius in 1865 in order to construct the exact differential dS = Q/T , where Q is the heat transfer and the absolute temperature T its integrating factor. A few years later, in the period 1872-1877, it was shown by Boltzmann that this quantity can be expressed in terms of the probabilities associated with the microscopic configurations of the system. We refer to this fundamental connection as the Boltzmann-Gibbs (BG) entropy, namely (in its discrete form) , where k is the Boltzmann constant, and {p _i} the probabilities corresponding to the W microscopic configurations (hence ∑^W _i=1 p _i = 1 . This entropic form, further discussed by Gibbs, von Neumann and Shannon, and constituting the basis of the celebrated BG statistical mechanics, is additive. Indeed, if we consider a system composed by any two probabilistically independent subsystems A and B (i.e., , we verify that . If a system is constituted by N equal elements which are either independent or quasi-independent (i.e., not too strongly correlated, in some specific nonlocal sense), this additivity guarantees S_BG to be extensive in the thermodynamical sense, i.e., that in the N ≫ 1 limit. If, on the contrary, the correlations between the N elements are strong enough, then the extensivity of S_BG is lost, being therefore incompatible with classical thermodynamics. In such a case, the many and precious relations described in textbooks of thermodynamics become invalid. Along a line which will be shown to overcome this difficulty, and which consistently enables the generalization of BG statistical mechanics, it was proposed in 1988 the entropy . In the context of cybernetics and information theory, this and similar forms have in fact been repeatedly introduced before 1988. The entropic form S_q is, for any q 1 , nonadditive. Indeed, for two probabilistically independent subsystems, it satisfies . This form will turn out to be extensive for an important class of nonlocal correlations, if q is set equal to a special value different from unity, noted q_ent (where ent stands for entropy . In other words, for such systems, we verify that , thus legitimating the use of the classical thermodynamical relations. Standard systems, for which S_BG is extensive, obviously correspond to q _ent = 1 . Quite complex systems exist in the sense that, for them, no value of q exists such that S_q is extensive. Such systems are out of the present scope: they might need forms of entropy different from S_q, or perhaps --more plainly-- they are just not susceptible at all for some sort of thermostatistical approach. Consistently with the results associated with S_q, the q -generalizations of the Central Limit Theorem and of its extended Lévy-Gnedenko form have been achieved. These recent theorems could of course be the cause of the ubiquity of q -exponentials, q -Gaussians and related mathematical forms in natural, artificial and social systems. All of the above, as well as presently available experimental, observational and computational confirmations --in high-energy physics and elsewhere-- are briefly reviewed. Finally, we address a confusion which is quite common in the literature, namely referring to distinct physical mechanisms versus distinct regimes of a single physical mechanism. This paper is part of the Topical Issue Statistical Power Law Tails in High-Energy Phenomena.     

航空飞行试验工程大数据管理与应用思考

飞行试验是航空装备研制的重要环节之一,形成和产生的工程数据具有明显的大数据特征。传统的以试验测试数据为主的数据管理思想,难以保证试飞工程数据及其关系的完整性和准确性,无法全面表征飞行试验全过程,不利于试飞数据的再利用。在分析航空飞行试验复杂系统工程的有机组成及其工程大数据的本质特征和逻辑结构的基础上,结合近年来在飞行试验数据管理和处理研究中取得的技术成果和实践经验,提出了基于试飞工程全生命周期的航空飞行试验工程大数据管理思想,以试验对象为中心的一体化大数据采集和系统化大数据结构模型,和面向业务的基于SOA的分布式系统框架,便于建立一个综合、全面、开放的试飞工程大数据管理和挖掘应用平台,促进航空产品试飞数据处理效率的提升和试飞工程大数据在航空科研中的挖掘和广泛应用,发挥试飞工程大数据的发展助推作用。