The Model Of Two Points Correlation Function For The Determination Of The Large Scale Structure Of The Universe (II)
Doru Marian Suran, Nedelia Antonia Popescu
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: suran@roastro.astro.ro, delia@roastro.astro.ro
Abstract. In this paper we investigate the inhomogeneities on large scale in the Universe. Our results indicate thet the signals of the inhomogeneities in different 3D catalogs ( galaxies, clusters, superclusters) are correlated, suggesting the presence of phase fluctuations in the long tail of the correlation function. The power spectrum P(k), the corresponding transfer function, the density fluctuation spectrum and peculiar velocity field of the LSU have been determined and plotted. In order to analyse the topological texture of the Universe at small, intermediate and large scale, we made different simulations.
Key words: cosmology - density fluctuation spectrum - peculiar velocity
field - large scale structure of the Universe - topological texture.
The Primordial Gravitational Waves With Cylindrical Symmetries
Iordana Astefanoaei, Gheorghe Maftei
Department of Theoretical Physics, "Al.I. Cuza" University,
Bd. Copou 11, RO-6600 Iasi, Romania
E-mail: iordana@uaic.ro
Abstract. We choose the cosmological model based on the Einstein-Tosen solution and we analyse the behaviour of gravitational waves in the primordial stages of Universe. The space-time defined by the Einstein-Rosen metric travels such as cylindrical pp gravitational waves when these ones are generated by the pure radiation field. Their evolution in the Einstein-Rosen space-time is given by the function p(z,t). The components of Riemann and Ricci tensors, and the scalar curvature invariant R are calculated in a null-tetradic base using the Newman-Penrose formalism. In the primordial stages of the Einstein-Rosen Universe, the potential function becomes zero, thus the relation (25) defines the wave equation. In this case there are gravitational perturbations travelling as gravitational waves. The Einstein-Rosen metric describes the Petrov-type gravitational waves.
Key words: gravitational wave - Einstein-Rosen solution - Newman-Penrose
formalism - energy-momentum pseudotensor - gravitational field.
Period Changes Of BW Vulpeculae: The Influence of Motion In A Binary System
Alexandru Horvath, Octavian Gherega, Ladislau Farkas
Astronomical Institute of the Romanian Academy,
Timisoara Astronomical Observatory
P-ta Axente Sever 1, RO-1900 Timisoara, Romania
Abstract. This paper presents the reduced photoelectric observational data on the variable star BW Vulpeculae obtained at Timisoara Astronomical Observatory. Using the moments of the observed minima and others from references, we computed a quadratic ephemeris describing a secular evolution. Removing the evolutionary term, from the O-C diagram, it still remains a periodicity. Assuming this due to the light-time effect in a binary system, these residuals allowed us to compute the orbital elements. Finally, we concluded that the period variation is described by the superposition of two separate physical effects: the evolution of the pulsating star and the orbital motion in a binary system.
Key words: Beta Cephei stars - BW Vulpeculae - photometry - period variation
- light time effect.
Gheorghe Dorin Chis
Astronomical Institute of the Romanian Academy,
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 RO-Cluj-Napoca, Romania
Abstract. The paper presents the photographic observations on VX Lacertae obtained at Astronomical Observatory of Cluj-Napoca during the years 1952-1953, 1961 and 1972. Our conclusion is that this binary is in the evolution phase of the first mass loss.
Key words: variable stars - binaries - photographic observations - mass
loss.
Time Structures Of Quasi-Periodic Patterns In Solar Radio Bursts
Adrian Oncica
Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: adrian@roastro.astro.ro
Abstract. We investigate a selection of (quasi) periodic structures, which are present in some solar radio bursts in search for physical processes signature. These structures include a wide range of phenomena from strictly sinusoidal oscillation up to quasiperiodic fine structure, observed in the radio, microwave and X-ray frequency range. Observational references are discussed, in order to give a key for the interpretation of observations. In this investigation, we use Joint Time-Frequency (JTF) spectrogram representations and scalogram (wavelet) representations. This was due not only to their ability to reveal the presence of dominant periods (as the usual spectrograms), but also to their ability to localize such spectral details in time.
Key words: solar physics - solar radio bursts - fine structure - time
frequency distribution.
Gravitational Redshift In Maneff'sField
Vasile Ureche
"Babes-Bolyai" University of Cluj-Napoca,
Faculty of Mathematics and Computer Science,
Str. M. Kogalniceanu 1, RO-3400 Cluj-Napoca, Romania
E-mail: vureche@math.ubbcluj.ro
Abstract. The gravitational redshift in Maneff's field is analysed. The results are expressed in terms of the ratio between the Schwarzschild gravitational radius and the geometric radius of the body, both for the special relativistic approximation and for the general relativistic approximation. In both cases the differece between the Newton's field and the Maneff's field in gravitational redshift is present only in the second order term and reaches 3/8 from the square of the above mentioned ratio. In general relativistic approximation, it is shown that an effect of black hole appears at a radius which we name Maneff gravitational radius and which is larger with the factor of 3/2 than the Schwarzschild gravitational radius.
Key words: relativistic astrophysics, gravitational redshift, Maneff
field.
The Schwarzschild - De Sitter Problem (I): Behaviour At Collision And Infinity
Vasile Mioc, Magda Stavinschi
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: vmioc@roastro.astro.ro, magda@roastro.astro.ro
Abstract. The Schwarzchild-de Sitter problem is being qualitatively tackled. The equations of motion are written in Hamiltonian formalism, and the first integrals of energy and angular momentum are pointed out. Using McGehee's transformations, the motion equations are regularized, and the collision singularity is replaced by the collision manifold M. Analogously, one introduces the infinity manifold. The flows on these manifolds and in their neighbourhood are depicted. They are identical to those corresponding to the Schwarschild problem for the collision manifold, and differ drastically for the infinity manifold.
Key words: celestial mechanics - Schwarzchild-de Sitter problem - McGehee
transformations.
The Elliptic Restricted Three-Body Problem. Constant Equipotential Surfaces.
Rodica Roman
"Babes-Bolyai" University, Faculty of Mathematics and Computer Science
Str. M. Kogalniceanu 1, RO-3400 Cluj-Napoca, Romania
E-mail: rroman@math.ubbcluj.ro
Abstract. The study of the elliptic restricted three-body problem is resumed and a peculiar case is considered. For the radius-vector an expansion in series is used, but only the non-periodic contribution is taken into account. A Jacobian integral is put in evidence and the positions of the Lagrangian points are determined.
Key words: celestial mechanics - three-body problem