摘要:

After some general remarks about‘big bang’cosmology it is pointed out how, in order to explain why there is matter but no antimatter in the observed Universe, reactions involving violation of baryon number must have taken place at early times. It turns out that processes violating time reversal invariance are also necessary. The article surveys the subjects of the discrete symmetries (space inversion, time reversal and particle-antiparticle transformation) and their violation in elementary-particle physics, and grand unified theories, which predict baryon number violation. A simple model is then presented which could account qualitatively for the dominance of matter over antimatter in the Universe. It is pointed out that grand unified theories are not the only providers of a mechanism for baryon number violation; one other possibility, the sphaleron, is briefly explained.

ISSN:0010-7514    

DOI:10.1080/00107519408229110

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

I explore a major controversy surrounding the physics of the aurora. Prevailing wisdom holds that the electrons causing bright and highly structured aurorae are accelerated into the upper atmosphere by a static electric field. It is argued here that this theory is so seriously flawed as to constitute a modern auroral myth. The evidence on which the theory was based and the reasoning that has served to preserve it in the face of numerous inconsistencies are briefly reviewed. An alternative theory is presented in which acceleration is caused by electrostatic waves. It is shown from first principles by means of a stylized Monte Carlo model that electrostatic waves could, if present in sufficient quantity, readily account for the consistently observed properties of the electrons. In considering wider implications of the wave theory, it is suggested that the aurora and other sites of wave acceleration of electrons in the plasmas of space may be natural manifestations of the process employed to energize plasmas in the laboratory in the drive towards controlled nuclear fusion.

ISSN:0010-7514    

DOI:10.1080/00107519408229111

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Cluster compounds represent an important class of molecules that lie between the bulk metal and conventional chemistry based on single metal centres. They contain three to 150 metal atoms bonded together by covalent bonds in a polyhedral arrangement that does not necessarily conform to that found in the bulk metal. Their electronic structure has been interpreted using free-electron spherical harmonic models that relate the polyhedral features to the total number of valence electrons in the molecule. The occurrence of these molecules raises interesting questions regarding the transition from metallic to non-metallic properties.

ISSN:0010-7514    

DOI:10.1080/00107519408229112

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A review of experimental research in neutron β-decay is presented, including the lifetime measurements and investigations of angular correlations. The experimental data, derived during the past 20 years, are analysed from the viewpoint of the modern theory of weak interactions. Various possible reasons for some contradictions between the latest most precise experiments and the theory predictions are discussed.

ISSN:0010-7514    

DOI:10.1080/00107519408229113

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519408229114

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519408229115

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519408229116

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Atmospheric ChangeBy T. E. Graedel and P. J. Crutzen 1993, £35·95 (hbk), £14·95 (pbk), pp. xiii + 446. Freeman, ISBN 0 7167 2332 8. Scope: text. Level: undergraduate.

ISSN:0010-7514    

DOI:10.1080/00107519408229117

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107519408229118

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor