[en] A series of disc galaxy models are constructed and their deformation in the tidal interaction is investigated by N-body simulations. Each galaxy model is composed of a self-gravitating disc made up of many particles and a rigid halo component added to stabilize the disc. Each model is characterized by two parameters; the mass fraction of the disc and the mass concentration of the halo toward the centre. These parameters are widely varied to investigate the dependence on internal structure whereas the relative motions of two galaxies are restricted to parabolic prograde planar encounters. It is found that the self-gravitating discs, when perturbed by the tidal force of another galaxy, develop prominent spiral structures not only in the outer region but also in the inner region. This is a remarkable contrast to the case of the massless discs constructed by test particles, in which only the outer part exhibits a spiral structure. (author)

[en] The inverse square law of gravitation is known to agree with astronomical data to very high accuracy, but recent theoretical and experimental work indicate that the inverse square law may be violated at distances less than 100 km. Such a violation would signal the existence of a new force. In order to check the inverse square law we are preparing to search for a non-newtonian force in a cylindrical shell. The cyclindrical shell has the property that the newtonian effects nearly cancel, so that we are doing a nearly null experiment. We have developed a superconducting gradiometer to measure the gravitational force gradients at the center of this cylindrical shell. By measuring both the vertical and horizontal gradients we can eliminate effects due to imperfections in the cylinder. This thesis describes the instrument and its performance as well as calculations of the sensitivity of the inverse square law test

[en] The results are given of detailed UBV photometry of the peculiar galaxy NGC 2685 based on 10 negatives obtained with the 2.6-m telescope of the Biurakan Observatory. Consideration of all the available observational data (photometric, spectroscopic, and polarization) suggests that NGC 2685 is a pair of colliding galaxies. 18 references

[en] The structural properties of the dwarf spheroidal satellite galaxies of the Milky Way may be strongly affected by their time-dependent interactions with the tidal field of the Milky Way. A low Q resonance of the tidal driving force with collective oscillation modes of the dwarf system can produce many of the observed properties of the Local Group dwarf spheroidal galaxies, including large velocity dispersions that would normally be interpreted as indicating large dynamical masses. 18 refs

[en] We propose a new mechanism by means of which a phase transition can be stimulated by self-gravitating matter. We suggest that this model could be used to explain the observed isotropy of the Universe. (orig.)

[en] A scalar-tensor theory of fourth-order gravity is considered. Some cosmological consequences, due to the presence of the scalar field, as well as of metric derivatives higher than second order, are analysed. In particular, upperbpunds are obtained for the coupling constant α and for the scale factor of the universe, respectively. The discussion is restricted to Robertson-Walker universes. (Author)

[en] The possible formation of bound hierarchical triple systems in globular clusters by encounters between single stars and binaries formed by tidal capture is considered. The first step in forming such systems must be the formation of temporarily bound hierarchical resonances. This paper explores the creation of such resonance systems in the context of globular clusters, taking into account both point mass and tidal effects. Numerical simulations show that relatively long-lasting systems can be formed, but only in retrograde or near retrograde orbits. A total cross section for the formation of relatively long-lasting triples on the order of that for the formation of tidal capture binaries is determined. The very low energy of the incoming stars appropriate for interactions in globular clusters is crucial for the formation process. 33 refs

[en] We have conducted an experiment to detect a composition-dependent force with range λ between 10 m and 1 km, and find a statistically significant effect. If interpreted as arising from a new force, this result and other recent measurementes would be consistent in strength only if the coupling were predominantly to nuclear isospin

[en] Specific features of a perpetually oscillating universe are considered. In a perpetually oscillating universe there is no problem of origination of the world, which in other versions of the universe may appear to be unsolvable. In the first section, the solution of the singularity problem is associated with the possible existence of asymptotic freedom for gravitational interactions. In the second section, the final state of a black hole is assumed to be a stable particle (maximon) of Planck mass and dimensions. (author)

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