This book represents the proceedings from the NATO sponsored Advanced Research Workshop entitled "Observational Tests of Inflation" held at the University of Durham, England on the 10th-14th December, 1990. In recent years, the cosmological inflation model has drawn together the worlds of particle physics, theoretical cosmology and observational astronomy. The aim of the workshop was to bring together experts in all of these fields to discuss the current status of the inflation theory and its observational predictions. The simplest inflation model makes clear predictions which are testable by astronomical observation. Foremost is the prediction that the cosmological density parameter, no, should have a value negligibly different from the critical, Einstein-de Sitter value of 00=1. The other main prediction is that the spectrum of primordial density fluctuations should be Gaussian and take the Harrison-Zeldovich form. The prediction that n =l, in patticular, leads to several important consequences o for cosmology. Firstly, there is the apparent contradiction with the limits on baryon density from Big Bang nucleosynthesis which has led to the common conjecture that weakly interacting particles rather than baryons may form the dominant mass constituent of the Universe. Secondly, with n =l, the age of the Universe is uncomfortably short if o the Hubble constant and the ages of the oldest star clusters lie within their currently believed limits.

When my colleague Dr. Paul Kent asked me which branch of Physics was most lively and which would lend itself best to a small high quality Symposium, I had no hesitation in answering 'Cosmology'. It seemed very timely that a meeting should take place which would bring together scientists interested in all branches of Astronomy, including Cosmic Rays, and Elementary Particles too and endeavour to put at least some of the pieces of the jigsaw together. The vast majority of the papers presented were later produced ~n appropriate camera-ready form and are published in this volume. I am very grateful to the authors for their ready cooperation. Grateful thanks are also extended to the Board of Management of the Foster-Wills and Theodor Heuss Scholarships, Oxford University and the Deutscher Akademischer Austauschdienst (German Academic Exchange Service) who funded the Symposium. The Director of the German Academic Exchange Service, Frau M.E. Schmitz and her colleague Mrs. Susan Putt, organized the whole meeting in a most exemplary fashion. Finally, on behalf of all participants and guests, s~ncere thanks are offered to Paul Kent as Convenor for initiating the Symposium, arranging the social events and organizing accommodation in such magnificent surroundings. Christ Church was the horne of Lewis Carrol and we were ever mindful - and appropriately so - of Alice. A. W. Wolfendale Durham, February 10th, 1982 vii A. W. Wolfendale (ed.), Progress in Cosmology, vii.

Solar and geomagnetic variability are of considerable interest for scientists of many different persuasions and indeed one has the distinct impression that for the sun at least, there is direct relevance for mankind in general as the interrelation between solar and terrestrial phenomena is starting to be appreciated. From the vast time scale of interest in the variability field, attention was confined to the last 10,000 years in a NATO Advanced Research Workshop held from April 6 - 10, 1987 in Durham, England, and the present publication comprises the lectures given there. Such a Workshop was very timely in view of the impressive new data available from 14C analysis in dated tree rings and lOBe in polar ice cores, from natural palaeomagnetic records in lacustrine sediments and from archaeomagnetic material. Also to be mentioned are new studies of historical accounts of naked-eye sunspots and aurorae. All the data have contributed to improvements in under standing the relative variations of solar properties, the geomagnetic field and climate and it is hoped that this volume will convey the flavour of these advances in knowledge. A feature of the Workshop was the lively discussions which followed so many of the papers. There were several instances of healthy disagreement and this is reflected in the opposing views presented inanumber of the papers published here."

This book represents the proceedings from the NATO sponsored Advanced Research Workshop entitled "Observational Tests of Inflation" held at the University of Durham, England on the 10th-14th December, 1990. In recent years, the cosmological inflation model has drawn together the worlds of particle physics, theoretical cosmology and observational astronomy. The aim of the workshop was to bring together experts in all of these fields to discuss the current status of the inflation theory and its observational predictions. The simplest inflation model makes clear predictions which are testable by astronomical observation. Foremost is the prediction that the cosmological density parameter, no, should have a value negligibly different from the critical, Einstein-de Sitter value of 00=1. The other main prediction is that the spectrum of primordial density fluctuations should be Gaussian and take the Harrison-Zeldovich form. The prediction that n =l, in patticular, leads to several important consequences o for cosmology. Firstly, there is the apparent contradiction with the limits on baryon density from Big Bang nucleosynthesis which has led to the common conjecture that weakly interacting particles rather than baryons may form the dominant mass constituent of the Universe. Secondly, with n =l, the age of the Universe is uncomfortably short if o the Hubble constant and the ages of the oldest star clusters lie within their currently believed limits.

Solar and geomagnetic variability are of considerable interest for scientists of many different persuasions and indeed one has the distinct impression that for the sun at least, there is direct relevance for mankind in general as the interrelation between solar and terrestrial phenomena is starting to be appreciated. From the vast time scale of interest in the variability field, attention was confined to the last 10,000 years in a NATO Advanced Research Workshop held from April 6 - 10, 1987 in Durham, England, and the present publication comprises the lectures given there. Such a Workshop was very timely in view of the impressive new data available from 14C analysis in dated tree rings and lOBe in polar ice cores, from natural palaeomagnetic records in lacustrine sediments and from archaeomagnetic material. Also to be mentioned are new studies of historical accounts of naked-eye sunspots and aurorae. All the data have contributed to improvements in under standing the relative variations of solar properties, the geomagnetic field and climate and it is hoped that this volume will convey the flavour of these advances in knowledge. A feature of the Workshop was the lively discussions which followed so many of the papers. There were several instances of healthy disagreement and this is reflected in the opposing views presented inanumber of the papers published here."

The cosmic radiation was discovered by Hess in 1912 but its origin is still the subject of much controversy and considerable study. For several decades most workers in the cosmic ray field were interested in the Nuclear Physical aspect of the particle beam and many important dis coveries were made, notably the identification of the positron, the muon, the pion and the strange particles. More recently however, em phasis has changed to the Astrophysical aspect both with re8ard to the origin of the radiation and to its relation with the other radiation fields. Mindful of the increasing importance of the Astrophysical facets of the subject the Cosmic Ray Commission of IUPAP approached the High Energy Astrophysics Commission of the IAU with the suggestion of a joint Symposium on Cosmic Ray Origin. The plan was to bring together workers in all the various astronomical fields - from Radio, through Optical to Gamma Rays - with Cosmic Ray physicists and to fully explore the various interrelations. The approach was received with enthusiasm and this book contains the proceedings of the ensuing Symposium, (styled IUPAP/ IAU Symposium No. 94) which was held in Bologna from 11th - 14th June 1980. Virtually all the papers presented are reproduced here. The Scientific Organizing Committee chose the invited speakers whose papers formed the major scientific component of the meeting. Additional short contributed papers were also called for and very brief 2-page resumes (which have not been refereed) are given in the proceedings."