This volume is the documentation of the second Course on 'Neutron Stars, Active Galactic Nuclei and Jets', held at Erice in September 1988. This second Course was devoted to our knowledge about neutron-star sources. The poster spoke of: pulsars, accreting X-ray sources and jet englnes, perhaps also UHE pulsars, X ra~' bursters and black-hole candidat.es. Neutron stars have even been proposed as the primary cosmic-ray boosters. Most of theil' properties are stil1 controversial, such as their birth mechanism (neutrino versus magnetic piston), internal structure (neutrons, quarks, strange particles), magnetic, thermal and spin histories, wind generation (hydrogen versus pair plasma, radiation versus centrifugal pressure), magnetospheric structure and accretion modes (along field lines versus quasi-Keplerian). The listed controversies have largely survived through the Course and entered into the proceedings. Several lecturers speak of 'magnetic-field decay' in neutron stars, of the 'recycling' of old pulsars, and of 'accretion-induced collapse' of white dwarfs as though such processes were textbook knowledge. Terms and abbreviations like RPSR (=recycled pulsar), spinup line, AIC, and ADC (=accretion disk corona) help to foster the assumptions. It is not clear to me at this time whether any of these notions has an application to reality.

This NATO AS! was the third in the series of Advanced Study Institutes on neutron stars, which started with 'Timing Neutron Stars', held in Qe§me near izmir, Turkey (April 1988), followed by 'Neutron Stars, an Interdis ciplinary Subject', held in Agia Pelagia on the island of Crete (September 1990). The first school centered on our main observational access to neu tron stars, i. e. the timing of radio pulsars and accretion powered neutron stars, and on what timing of neutron stars teaches us of their structure and environment. The second school had as its theme the interplay between diverse areas of physics which find interesting, even exotic applications in the extreme conditions of neutron stars and their magnetospheres. As the field has developed, with the number of observed neutron stars rapidly in creasing, and our knowledge of many individual neutron stars getting deeper and more detailed, an evolutionary picture of neutron stars has started to emerge. This led us to choose 'The Lives of the Neutron Stars' as the uni fying theme of this third Advanced Study Institute on neutron stars. Different types of neutron star activity have been proposed to follow one another in stages during the lives of neutron stars in the same basic population; the evolutionary connection between low-mass X-ray binaries and millisecond radio pulsars is perhaps the prime example.

Some twenty-three years after the discovery of pulsars and their identification as rotating neutron stars, neutron star physics may be regarded as comingofage. Pul sars and accreting neutron stars have now been studied at every wavelength, from the initial radio observations, through optical, X-, and "{-ray, up to the very recent observations in the TeV region, while theorists have studied in some detail relevant physical processes both outside and inside neutron stars. As a result, comparisonof theory with observation provides a test ofour theoretical ideas in fields as diverse as neutron and nuclear matter, superfluidity and superconductivity, the acceleration of high energy particles, and the generation and maintenance of intense magnetic fields. For example, through observations of glitches and post glitch behavior of pulsars, it has become possible to establish the presence ofsuperfluid neutron mat ter in the inner crust of neutron stars, and to determine some of its properties, while neutron stars in compact binary systems offer one ofthe most efficient energy generation mechanisms known. It is in fact the interactive interpretation of these ,diverse pieces of information that can lead to major advances in our understanding of the physics of these exotic objects, and justifies the characterization of neutron stars as hadron physics laboratories.

Proceedings of the NATO Advanced Study Institute, Elounda, Crete, Greece, 7-18 June 1999

A very attractive feature of the theory of general relativity is that it is a perfectexampleofa“falsi?able”theory:notunableparameterispresentinthe theory and therefore even a single experiment incompatible with a prediction of the theory would immediately lead to its inevitable rejection, at least in the physical regime of application of the aforementioned experiment. This fact provides additional scienti?c value to one of the boldest and most fascinating achievements of the human intellect ever, and motivates a wealth of e?orts in designing and implementing tests aimed at the falsi?cation of the theory. The ?rst historical test on the theory has been the de?ection of light gr- ing the solar surface (Eddington 1919): the compatibility of the theory with this ?rst experiment together with its ability to explain the magnitude of the perihelion advance of Mercury contributed strongly to boost acceptance and worldwideknowledge.However,technologicallimitations preventedphysicists from setting up more constraining tests for several decades after the formu- tion of the theory. In fact, a relevant problem with experimental general r- ativity is that the predicted deviations from the Newtonian theory of gravity areverysmallwhentheexperimentsarecarriedoutinterrestriallaboratories.

IAU Transactions are published as a volume corresponding to each General Assembly. Volume A is produced prior to the Assembly and contains Reports on Astronomy, prepared by each Commission President. The intention is to summarize the astronomical results that have affected the work of the Commission since the production of the previous Reports up to a time which is about one year prior to the General Assembly. Volume B is produced after the Assembly and contains accounts of Commission Meetings which were held, together with other material. The reports included in the present volume range from outline summaries to lengthy compilations and references.

Neutron stars hold a central place in astrophysics, not only because they are made up of the most extreme states of the condensed matter, but also because they are, along with white dwarfs and black holes, one of the stable configurations that stars reach at the end of stellar evolution. Neutron stars posses the highest rotation rates and strongest magnetic fields among all stars. They radiate prolifically, in high energy electromagnetic radiation and in the radio band. This book is devoted to the selected lectures presented in the 6th NATO-ASI series entitled "The Electromagnetic Spectrum of Neutron Stars" in Marmaris, Turkey, on 7-18 June 2004. This ASI is devoted to the spectral properties of neutron stars. Spectral observations of neutron stars help us to understand the magnetospheric emission processes of isolated radio pulsars and the emission processes of accreting neutron stars. This volume includes spectral information from the neutron stars in broadest sense, namely neutrino and gravitational radiation along with the electromagnetic spectrum. We believe that this volume can serve as graduate level of text including the broad range of properties of neutron stars.

Supernovae, their bearing on cosmology and their connection to gamma-ray bursts are now at the center of astrophysical research programs. This volume deals with astronomical observations of supernovae and their relation to nuclear and particle astrophysics. All known aspects of supernovae explosions are investigated in articles specifically written for researchers and advanced graduate students. It also includes recent numerical "experiments" related to the question of hydrodynamical instability in two and three dimensions and to problems concerning the complexity of radiation transport in the models. Other contributions discuss the possible energy sources needed to drive these powerful stellar explosions.

Neutron stars are the densest observable bodies in our universe. Born during the gravitational collapse of luminous stars - a birth heralded by spectacular supernova explosions - they open a window on a world where the state of the matter and the strengths of the fields are anything but ordinary. This book is a collection of pedagogical lectures on the theory of neutron stars, and especially their interiors, at the forefront of current research. It addresses graduate students and researchers alike, and should be particularly suitable as a text bridging the gap between standard textbook material and the research literature.