Scientific Publications 1 R. Ruffini and S. Bonazzola. Systems of Self-Gravitating Particles in General Relativity and the Concept of an Equation of State, Physical Review 187,1767-1783 (1969). A method of self--consistent fields is used to study the equilibrium configurations of a system of self--gravitating scalar bosons of spin--1/2 fermions in the grounds state without using the traditional perfect-fluid approximation or equation of state. The many--particle system is described by a second--quantized free field, which in the boson case satisfies the Lein--Gordon equation in general relativity, $\nabla_\alpha \nabla^\alpha\phi =\mu^2\phi$, and in the fermion case the Dirac equation in general relativity $\Upsilon_\alpha \nabla^\alpha \psi = \mu \psi $(where $\mu = mc/h$). The coe~cients of the metric $\delta \alpha \beta$ are determined by the Einstein equations with a source term given by the mean value $\langle \phi \vert\tau_\mu\nu\vert \phi \langle$ of the energy--momentum tensor operator constructed from the scalar or the spinor field. The state vector $\langle \phi\vert$ corresponds to the ground state of the system of many particles. In both cases, for completeness, a nonrelativistic Newtonian approximation is developed, and the corrections due to special and general relativity explicitly are pointed out. For $N$ bosons, both in the region of validity of the Newtonian treatment (density from $10^-80$ to $10^54gcm^-3$, and number of particles from 10 to $10^40$) as well as in the relativistic region (density $\sim 10^54gcm^-3$, number of particles $\sim 10^40$, we obtain results completely different from those of a traditional fluid analysis. The energy--momentum tensor is anisotropic. A critical mass is found for s system of $N \sim $[(Planck mass)/m]$^2\sim 10^40$ (for $m \sim 10^-25$) self--gravitating bosons in the ground state, above which mass gravitational collapse occurs. For $N$ fermions, the binding energy of typical particles is $G^2m^5N^4/3 \hbar^-2$ and reaches a value $\sim mc^2$ for $N \sim N_crit \sim$ [(Planckmass)/m]$^3 \sim 10^57$ for $m \sim 10^-24$ g, implying mass $\sim 10^33$ g, radius $\sim 10^6$ cm, density $\sim 10^19g/cm^3$. For densities of this order of magnitude and greater, we have given the full self--consistent relativistic treatment. It shows that the concept of an equation of state makes sense only up to $10^42 g/cm^3$, and it confirms the Oppenheimer--Volkoff treatment in extremely good approximation. There exists a gravitational spin--orbit coupling, but its magnitude is generany negligible. The problem of an elementary scalar particle held together only by its gravitational field is meaningless in this context. $$N_crit \sim [Planck mass/m]^2$$ while for N fermions: $$N_crit \sim [Planck mass/m]^3.$$ 2 A. Ferrari and R. Ruffini. Theoretical Implications of the Second Time Derivative of the Pulsar NP0532, Astrophys. J. Letters158, L71(1969) Even in the early days of Pulsar Astrophysics it became clear that much information could be gained on the nature of these objects by analysing the change of their period. In particular, quite apart from sudden changes in the pulsar period ("glitches"), an analysis of the second derivative with respect to time of the pulsar period could give important information on the breaking mechanism of the rotating neutron star. In this work, which uses techniques of a low velocity approximation of relativistic theories, an analysis is made of the emission of gravitational radiation from rotating neutron star as being the possible consequence of asymmetries in the equatorial plane. The results from breaking are due to gravitational radiation and from breaking due to electromagnetic radiation from an offaxis magnetic field are compared and contrasted. Suggestions are also made for estimating the possibk lifetime of the Pulsar. We were able to confront these theoretical predictions with the results of Pulsar Timing. These results have allowed us to impose limits on the eccentricities of neutron stars in pulsars. Scientific Publications 3 R. B. Partridge and R. Ruffini. Gravitational Waves and a Search for the Associated Microwave Radiation., Gravity Research Foundation. Third Award. 12pp. 1970. We discuss astronomical sources which might produce the pulses of gravitational waves reported by Weber (3). A fraction of the energy emitted by such sources may emerge as electromagnetic pulses associated with the reported gravitational events. We observe the galactic center at a favorable microwave frequency, 19 GHz. The directional sensitivity of Weber's detector (given below) is a maximum during our observing period, allowing a direct comparison between our data and his. If positive correlations are found, the propagation velocity of gravitational waves can be determined to one part in $10^11$. 4 R. Ruffini. Gravitational Waves., Invited talk, 30 minutes, Particle and Field Section of the American Physical Society, Austin, Tx. 5.XI. 1970. In this section, following an invited talk by J. Weber, Ruffini critically analyzed the energy problem connected with the explanation of Weber's events as being due to gravitational radiation bursts. This talk was based mainly on the theoretical work of Ruffini and Wheeler, leading for the first time to a rigorous analysis of gravitational wave detectors and their estimated cross--section. 5 Remo Ruffini Relativistic Cosmology and Space Platforms., Institute for Advanced Study, Princeton, New Jersey and John--Archibald Wheeler--Joseph Henry Laboratories, Princeton University, Princeton, New Jersey. ESRO Pub., A.F. Moore and V. Hardy. 1971. Einstein's standard 1915 general relativity or geometrodynamics introduces a new dynamic participant on the scene of physics: geometry. Nowhere did the dynamics of geometry originally show up more impressively than in the expansion of the Universe. Today the role of curved space geometry, both static and dynamic, lends itself to investigation from space platforms or from the ground. or both, in many other contexts. Among those discussed here are: properties of a superdense or neutron star; pulsar physics; collapse of a star with big dense core to a superdense star in a supernova event or complete collapse to a black hole; physics of the black hole; galactic centers, jets, and quasi--stellar sources; gravitational radiation; Misner's mixmaster model of the universe; the primordial fireball radiation; the time--scale of the expansion of the Universe; the Universe as a lens, magnifying the apparent diameter of a far--away galaxy; the mystery of the missing matter; the formation of galaxies; reaching out via radiation receivers for more information on the physics of these phenomena; and finally the solar system itself as a testing ground for relativity including the traditional three tests of relativity; the retardation of light as it passes close to the Sun on its way to Venus and back; relativistic effects in planetary motion and searches via corner reflectors on the Moon for relativistic effects in the motion of the Moon, as predicted by Baierlein. 6 R. Ruffini. Sources of Gravitational Radiation., Invited talk, 30 minutes. New Orleans meeting of the American Physical Society. This was the first invited talk given by R. Ruffini, and was presented at a meeting of the American Physical Society. During this meeting, W.O. Hamilton of Louisiana State University and W.M. Fairbank of Stanford University presented the research program for the super--cooled gravitational waves antenna. In his talk, Ruffini presented the first evidence for the possibility of detecting a large amount of gravitational radiation from material accelerated in the field of collapsed objects. This research program was developed and presented by him and his students and collaborators in further papers. Scientific Publications 7 C.E. Rhoades, Jr. and R. Ruffini. Hagedorn Equation of State in Neutron Stars., Astrophysical Journal Letters, 163, L83 . 1971 At a density of 5 x 10 gr/cm neutron star matter can be described by a system of three non--interacting degenerate gasses: electrons, protons, and neutrons. At densities 10 gr/cm and greater, strong interactions between particles can make significant contributions. At densities of 10 gr/cm, the production of new particles and resonances has to be taken into account. Under these conditions the equation of state proposed by Hagedorn, applies. In this work Rhoades (a graduate student of Ruffini's) and Ruffini have analyzed the effects of this equation of state in the computation of the equilibrium configuration of a neutron star. The authors, were able for the first time, to point out both the new effects of the "softening" of the equation of state towards high densities and the "saturation" of the value of the mass of the neutron star as a function of its central density, and as a consequence of the generation of the particles and resonances. A critical analysis of these results together with a study of the physical reasons originating from these results were presented by C. Rhoades in his doctoral thesis at Princeton University (advisor was R. Ruffini) and by R. Ruffini in his Les Houches lectures (see further). 8 R. Ruffini. Emission of Gravitational Waves from the Pulsar. In the Crab Nebula., Davies and Smith eds. H. Reidel. 1971 In this talk, given at the International Astronomical Union meeting held in Manchester in 1971, the author pointed out the relevance of the classical analysis of McLaurin, Poincare, Darwin, Jacobi and Jeans on the configuration of rotating fluid masses for the emission of gravitational radiation. Together with numerical estimates of the strength of the emitted radiation, the author presented evidence for the possibility of obtaining information on the internal structure of the neutron star from the existence of a large emission of gravitational radiation. The "signature" of the gravitational radiation emitted in these processes was also examined.