光谱与氢原子之间无区别

<正>物质与反物质之间的极端不平衡是宇宙中最令人困惑的谜题之一。它们都是在大爆炸期间产生,但如今占统治地位的却是普通物质,其缘由我们不得而知。要解决这一谜题,最显而易见的方法便是观察反物质本身。如果科学家能够发现反物质的行为有某种不同,或许就能找到解释这种极端不平衡的线索。为此,研究人员决定对氢原子和反氢原子是否具有相同的光谱——吸收和释放相同波长的光——进行测     

威力强大的反物质

根据丹·布朗的巨著拍摄的一部电影,为我们提供了另一种假设在瑞士日内瓦附近的粒子物理实验室生成的危险物——反物质,用这种物质制成的武器具有非凡的破坏力。虽然布朗书中的反物质是虚构的,但是这种物质本身并不是虚构的。我们在宇宙射线里就能看到它的迹象,科学家通过在世界各地的粒子加速器里进行高能撞击,制成这种物质。     

“核能星舰”花50年可载人类抵达半人马座

不需虫洞不需反物质引擎,利用最新科技,人类有生之年进行星际旅行不是梦——据美国最新一期《天文学》杂志报道,人类进行"星际旅行"迄今仍然只是科幻小说或科幻电影中的情节,多年来,虽然科学家们一直在探讨如何利用虫洞、反物质动力引擎、"亚光速飞船"等未来科技进行星际旅行的可能性,但很少有人相信在未来50年到     

狄拉克的科学思想

狄拉克是二十世纪最杰出的理论物理学家之一。他对量子力学的建立和发展,作出了重大贡献;他所建立的相对论性电子理论,预言了反物质(正电子)的存在,从而改变了人们对物质和真空的认识,使二十世纪的自然观发生了深刻的变化。狄拉克在现代物理学史上占有极为崇高的地位,是一件举世公认的事实。比如,海森伯认为:“对于本世纪本质上崭新的物理图象的建立来说,是普朗克发现作用量子的贡献大,还是狄拉     

揭秘反物质

据英国《新科学家》杂志报道，不久前我们听说欧洲粒子物理研究所利用大型强子对撞机产生可摧毁行星的黑洞。现在根据丹·布朗的巨著拍摄的一部电影，为我们提供了另一种假设在瑞士日内瓦附近的粒子物理实验室生成的危险物——反物质，用这种物质制成的武器具有非凡的破坏力。     

宇宙de诞生(下)

五、诺亚方舟各星球代表们纷纷返回自己的星球执行“休眠计划”,很快他们又携带光盘返回阿尔法星,邻近星系也将自己的燃料球运抵B恒星系中的正、反物质星球,诺亚方舟制成了,“盼盼”、“新生”这一对最优秀的青年也在阿尔法星上被挑选了出来。哈恩总督和各星球代表为这一对寄托着人类全部希望的青年举行了隆重的宣誓仪式。     

几克就能毁灭地球：美国反物质武器浮出水面

18年前，美国格林空军基地“革命性弹药”研发小组的负责入肯尼斯·爱德华兹。开始率队进行一项近乎“天方夜谭”的工作——反物质武器的研究；18年后，当这种威力超过原子弹的划时代新武器就要浮出水面时，人们不禁担心：它可能引发一场“地球灭绝战争”。     

科学家发现未知梨形原子核

《自然》杂志刊载了一篇此前未知的梨形原子核的文章,这种不规则形状的原子核将有望颠覆传统的原子物理理论,并揭开宇宙中物质多于反物质的谜团。原子核是由强核力聚合在一起的,这种力必须克服质子间的静电斥力而将原子核聚集在一起。然而要想使用第一性原理来计算这些粒子间的相互作用是非常复杂的,因此理论物理学家们提出了一些有时是相互矛盾的模型来描述原子核结     

大师的“无知”

正丁肇中曾给南航师生作报告,有学生问:"您觉得人类在太空能找到暗物质和反物质吗?"他回答:"不知道。"又有学生问:"您觉得您从事的科学实验有什么经济价值吗?"他又回答:"不知道。"有学生又问:"您能不能谈谈物理学未来20年的发展方向?"他仍     

大型强子对撞相建造完成——我国科学家积极参与并做出重要贡献

大型强子对撞机（Large Hadron Collider,LHC）是在欧洲核子中心（CERN）建造的当今最大的高能物理科学实验装置。科学家期待用它来模拟和重现宇宙大爆炸后一万亿分之一秒时的能量和条件,通过仔细分析撞击产生的残骸,以验证粒子物理学的标准模型,并研究探索反物质和暗物质。LHC装置和实验受到国际科学界和社会公众的广泛关注,预期将推动物理学进入崭新阶段。     

风险社会中的科技伦理:问题与出路

风险社会是全球化时代不可避免的境遇,风险社会中关于科技伦理的理解发生重大变化,也使科技伦理本身的发展面临重大问题与困境.导致这种困境的原因是多方面的.本文认为,基于人类整体的和未来的根本利益具有普世意义的科技伦理价值观应当成为我们不懈的追求,科技伦理与科学技术发展的历史循环、对私人利益与公共利益的分裂与对立的历史性批判是走出困境寻求出路的根本思路.     

Some Epistemic Questions of Cosmology

We discuss a number of fundamental aspects of modern cosmological concepts, from the phenomenological, observational, theoretical and epistemic points of view. We argue that the modern cosmology, despite a great advent, in particular in the observational sector, is yet to solve important problems, posed already by the classical times. In particular the stress is put on discerning the scientific features of modern cosmological paradigms from the more speculative ones, with the latter immersed in some aspects deeply into mythological world picture. We finally discuss the principal paradigms, which are present in the modern cosmological studies and evaluate their epistemic merits.     

A Combinatorial Approach to Assess the Separability of Clusters

Separability of clusters is an issue that arises in many different areas, and is often used in a rather vague and subjective manner. We introduce a combinatorial notion of interiority to derive a global view on separability of a set of entities. We develop this approach further to evaluate the overall separability of a partition in the context of cluster analysis. Our approach captures combinatorial and geometrical aspects of data and provides, in addition to numerical evaluations, graphical representations particularly useful when data are not easily visualized. We illustrate the methodology on some real and simulated datasets.     

The MAP test for multimodality

We introduce a test for detecting multimodality in distributions based on minimal constrained spanning trees. We define a Minimal Ascending Path Spanning Tree (MAPST) on a set of points as a spanning tree that has the minimal possible sum of lengths of links with the constraint that starting from any link, the lengths of the links are non-increasing towards a root node. We define similarly MAPSTs with more than one root. We present some algorithms for finding such trees. Based on these trees, we devise a test for multimodality, called the MAP Test (for Minimal Ascending Path). Using simulations, we estimate percentage points of the MAP statistic and assess the power of the test. Finally, we illustrate the use of MAPSTs for determining the number of modes in a distribution of positions of galaxies on photographic plates from a rich galaxy cluster.     

A Burgessian Critique of Nominalistic Tendencies in Contemporary Mathematics and its Historiography

We analyze the developments in mathematical rigor from the viewpoint of a Burgessian critique of nominalistic reconstructions. We apply such a critique to the reconstruction of infinitesimal analysis accomplished through the efforts of Cantor, Dedekind, and Weierstrass; to the reconstruction of Cauchy’s foundational work associated with the work of Boyer and Grabiner; and to Bishop’s constructivist reconstruction of classical analysis. We examine the effects of a nominalist disposition on historiography, teaching, and research.     

On lattice consensus methods

We investigate the consensus problem for classifications of three types: partitions, dendrograms, and n-trees For partitions or dendrograms, lattice polynomials define natural consensus functions We extend these lattice methods to n-trees, introducing a general class of consensus functions that includes the intersection consensus functions in current use These lattice consensus methods have a number of desirable mathematical properties We prove that they all satisfy the Pareto Axiom For each of the three classification types, we determine which lattice consensus functions satisfy the Betweenness AxiomAuthor partially supported by a research grant from the Faculty Research Committee, Bowling State University     

Anthropomorphic Quantum Darwinism as an Explanation for Classicality

According to Zurek, the emergence of a classical world from a quantum substrate could result from a long selection process that privileges the classical bases according to a principle of optimal information. We investigate the consequences of this principle in a simple case, when the system and the environment are two interacting scalar particles supposedly in a pure state. We show that then the classical regime corresponds to a situation for which the entanglement between the particles (the system and the environment) disappears. We describe in which circumstances this factorisability condition is fulfilled, in the case that the particles interact via position-dependent potentials, and also describe in appendix the tools necessary for understanding our results (entanglement, Bell inequalities and so on).     

Graph Partitioning by Correspondence Analysis and Taxicab Correspondence Analysis

We consider correspondence analysis (CA) and taxicab correspondence analysis (TCA) of relational datasets that can mathematically be described as weighted loopless graphs. Such data appear in particular in network analysis. We present CA and TCA as relaxation methods for the graph partitioning problem. Examples of real datasets are provided.     

Contours and Tight Clusters

Nested clusters arise independently in graph partitioning and in the study of contours. We take a step toward unifying these two instances of nested clusters. We show that the graph theoretical tight clusters introduced by Dress, Steel, Moulton and Wu in 2010 are a special case of nested clusters associated to contours.