We present the results of an imaging survey to search for gravitationally lensed arcs in a sample of 40 EMSS clusters of galaxies. The lensing frequency obtained suggests that the X-ray selection is the preferred method for finding true, massive clusters which are more likely to exhibit the lensing phenomenon.

TAUVEX is a three-telescope array intended to image wide sky areas in the UV. It is being constructed in Israel for flying on-board the Spectrum X-γ (SRG) international high-energy observatory. SRG will be orbited by Russia in early 1996 for a three-year+ mission. TAUVEX will operate in parallel with X-ray imaging telescopes on board SRG to provide time-resolved photometry and deep UV imaging.

There have been claims from time to time that there are periodicities in the redshift distribution of QSOs. These claims are examined from various statistical angles for a sample of 2164 QSO redshifts, with redshifts lying in the range 0.025 – 4.43 taken from the latest compilation (1993) by Hewitt & Burbidge. We have not included QSOs whose redshifts were obtained by ‘grism’ technique, because of a possible selection effect (Scott 1991). For our analysis we use several staistical techniques, including the Burbidge - O'Dell type Power spectrum analysis (1972), the Rayleigh test, the Kolmogorov-Smirnov test, and the so called ‘Comb-tooth’ template test. the tests are not inter related and have the advantage of checking the claim for nonuniformity of the distribution from various independent angles. We have also carried out Monte Carlo simulations of the redshift distribution of QSOs to check for any systematic effect that can give rise to a spurious periodic effect.

“Eternal” Inflation has relevelled the creation of universes, making it a “routine” physical occurence. The mechanism of the Big Bang, from the conditions triggering it, to the eventual creation of the entire matter content of the resulting universe, involves no singular physical processes. However, causal horizons, due to General Relativity, separate the newborn universe from the parent universe in which it was seeded as a localized vacuum energy. The new universe's expansion only occurs “after” infinite time, i.e. “never”, in the parents frame. This forces a reassessment of “reality”. The two universes are connected by the world line of the initial localized vacuum energy, originating in the parent universe. Assuming that the parent universe itself was generated in a similar fashion, etc., an infinite sequence of previous universes is thus connected by one world-line, like a string of beads.

The radiative decay of massive relic 30eV neutrinos could explain several observational puzzles including the missing dark matter in the universe and the anomalous degree of ionization of interstellar matter in the Galaxy. We note that various non-standard particle physics models with extended scalar sector or minimal supersymmetry have sufficient freedom to accommodate such neutrinos. We discuss observational constraints in the immediate Solar neighborhood, in nearby regions of low interstellar absorption, in the Galactic halo, in clusters of galaxies, and in extragalactic space. Although some observations have been interpreted as ruling out this picture, we note that this is true only for models in which extreme concentrations of neutrinos occur in clusters of galaxies. An instrument is under development to measure the cosmic diffuse EUV background in the local Solar neighborhood, for flight on the Spanish Minisat satellite platform. This instrument will have the capability of providing a definitive test of the radiative neutrino decay hypothesis.

At the last time the concept of the curved space-time as the some medium with stress tensor σαβ on the right part of Einstein equation is extensively studied in the frame of the Sakharov - Wheeler metric elasticity(Sakharov (1967), Wheeler (1970)). The physical cosmology pre- dicts a different phase transitions (Linde (1990), Guth (1991)). In the frame of Relativistic Theory of Finite Deformations (RTFD) (Gusev (1986)) the transition from the initial state of the Universe (Minkowskian's vacuum, quasi-vacuum(Gliner (1965), Zel'dovich (1968)) to the final state of the Universe(Friedmann space, de Sitter space) has the form of phase transition(Gusev (1989) which is connected with different space-time symmetry of the initial and final states of Universe(from the point of view of isometric group Gn of space). In the RTFD (Gusev (1983), Gusev (1989)) the space-time is described by deformation tensor of the three-dimensional surfaces, and the Einstein's equations are viewed as the constitutive relations between the deformations ∊αβ and stresses σαβ. The vacuum state of Universe have the visible zero physical characteristics and one is unsteady relatively quantum and topological deformations (Gunzig & Nardone (1989), Guth (1991)). Deformations of vacuum state, identifying with empty Mikowskian's space are described the deformations tensor ∊αβ, where the metrical tensor of deformation state of 3-geometry on the hypersurface, which is ortogonaled to the four-velocity is the 3 -geometry of initial state, is a projection tensor.

In the RTFD(Gusev (1986)) the conception of a Sakharov - Wheeler Metric Elasticity(SWME)(Sakharov (1967), Wheeler (1970)) had been worked out. On the basis of the exact solutions of Einstein equations and qualitative analysis RTFD the global evolution have been studied and the phase portraits of the early Universe is being constructed. An analysis of phase portraits show on the possibility description of spontaneous creation of Universe from an initial Minkowskian's vacuum to an inflationary de Sitter space-time in the frame of phenomenological non-quantum theory (Guth (1991)). During the past decade, a radically new picture of cosmology has emerged. The present homogeneous expanding Universe would have stated out with a de Sitter phase. The purpose of this paper is to shown that the geometry-dynamical approach to the Einstein's gravitation theory in the frame RTFD also is leaded to the nonsingular cosmological models (Brandenberger (1993)). Let us to propose that before the some moment of time the Universe is at the vacuum state and is described the geometry of Minkowskian's space. Deformations of vacuum state, identifying with empty Mikowskian's space are described by the deformations tensor , An arising of deformation ∊αβ is leaded to appearance of the stress tensor ∊αβ and the energy-momentum Tαβ(∊γδ) which is connected with “creating” particles in the Universe. Here we are considered the deformations of Minkowskian's space (the initial vacuum state with ∞ αβ = 0) at the linear theory (~ ∊) of finite deformations. The final deformation state gαβ are searched in the metric class of Friedmann's cosmological spaces. In the comoving reference system Uα(0, 0, 0, 1) the Friedmann's equations have form (Narlikar & Padmanabhan (1983), and Gusev (1989)): where R(t) is so called the expansion factor at the Robertson - Walker line element, k is the curvature parameter with the possible values −1, 0, + 1, P is pressure, k1, k2 are the some combination from a Lame coefficients, l02 is a “initial radius” Universe, a free parameter model. The phase space of this model is the two-dimensional (R, Ṙ) plane. We note that there is only two singular points (Ṙ = 0, Ṙ = 0) in the phase plane. The one of those points is R = l0, Ṙ = 0 and corresponds to Minkowski space - time. There are two classes trajectories which are asymptotically de Sitter. Those starting at large positive values of Ṙ go off to Ṙ = + ∞, reaching their asymptotic value of H from above. Those starting with large negative values of Ṙ tend to R = + ∞ with Ṙ > 0. For small values of Ṙ and R we can see that there are periodic solutions about Minkowski space. The corresponding solutions oscillate with frequency given by H0 (which is possible equal planck scale) about Minkowski space. Based on the preceding discussion of asymptotic solutions we see that there is a separatrix (Gusev, (1989)) in phase space dividing solutions which tend to R = + ∞ from those which oscillate or tend to R = l0. The above analyses of the phase portraits is an indication that in our theory Minkowski space may be unstable toward homogeneous deformations. We stress that all the general features of the phase portrait analyses are true for quadratic deformations of gravitational vacuum. Our model incorporates a very important feature: in the asymptotic de Sitter region, the quadratic deformations and temperature effects does not have an important effect on the geometry. The effective gravitational constant of coupling goes to zero as space - time approaches de Sitter space. In this sense the model is asymptotically free (gravitational confinement Linde, (1990)). At the late times the solutions are described a evolution of the de Sitter Universe R~expHt (Hoyle et al. (1993)).

The stability problem in cosmology is studied using the equations of geodesic deviation. General conditions for stability are obtained. The method is applied to a number of cosmological models, resulting from different field theories. The results are compared with those obtained from FRW -models.

To solve some of the problems of standard cosmology, the Absolute Parallelism (AP) space is used to construct alternative field theories other than GR. Four different field theories are being reviewed. The consequences of their cosmological applications are being compared with those of GR. The results are promising and show that more investigations, concerning this space, are needed, especially generalization of the singularity theorems.

We have developed and tested a code that computes the evolution of a mixed system of gas and dark matter in expanding world models. The gravitational forces are calculated with the Adaptative P3M algorithms developed by H. Couchmann, 1993. The calculation of gas forces follow the standard SPH formalism (Monaghan, 1989).