Cosmological application of the New General Relativity

The field equations of the New General Relativity NGR, constructed by Hayashi and Shirafuji (1979), have been applied to two geometric structures, given by Robertson (1932), in the domain of cosmology. In the first application a family of models, involving two of the parameters characterizing the field equations of the NGR, is obtained. In the second application the models obtained are found to involve one parameter only. The cosmological parameters in both applications are calculated and some cosmological problems are discussed in comparison with the corresponding results of other field theories .     

The population of binary and millisecond pulsars

Recent searches for millisecond and binary pulsars are reviewed, with particular emphasis on the nearly complete Parkes southern survey. Correlations between several of the major parameters of these systems are discussed.     

Orbit determination by four observations

An elliptic orbit is determined from two short-arc pairs of observations at different oppositions by the angular momentum integral. Other methods for initial orbit determination than the classical do exist.     

Neutron stars in the multidimensional einstein theory of gravitation

The radius, mass, total number of baryons, and other parameters of static, spherically symmetric, superdense stars are calculated. A model with one Ricci-flat inner space of arbitrary dimensionality and the approximation p₁=?0.5ε + ap for additional components of the energy — momentum tensor are used (ε and ρ are the total energy density and the pressure of the stellar matter and a is a fitting parameter). In the case of white dwarfs, the results of the multidimensional theory do not depend on the dimensionality D of space-time for ?10 ? a ? 10 and coincide with the analogous data of the general theory of relativity (GTR). For neutron stars there is a dependence on D and a. For D>4, in particular, the greatest mass M_max of a neutron star as a function of a has a maximum at 3<a(D) ? 4, which exceeds the greatest mass M _max ⁰ =2.14 M_⊙ in the GTR. A comparison of theoretical results with observational data determines the allowable values of a. Data for PSR 1913 + 16 lead to 0.2 ≤ a ≤ 9.2 in the case of D=26, while the results of [P. C. Joss and S. A. Rappaport, Annu. Rev. Astron. Astrophys.,22, 537 (1984)] lead to the stricter limits 1 ≤ a ≤ 7.4.     

Evolving Photospheric Flux Concentrations and Filament Dynamic Changes

We analyze the role of weak photospheric flux concentrations that evolve in a filament channel, in the triggering of dynamic changes in the shape of a filament. The high polarimetric sensitivity of THEMIS allowed us to detect weak flux concentrations (few Gauss) associated with the filament development. The synoptic instruments (MDI, SOLIS) even if their sensitivity is much less than THEMIS were useful to follow any subsequent strengthening of these flux concentrations after their identification in the THEMIS magnetograms. We found that (1) the northern part of the filament develops an Hα barb at the same time that weak minority polarity elements develop near a plage; (2) a section in the southern part of the Hα filament gradually disappears and later reforms at the same time that several mixed-polarity magnetic elements appear, then subsequently cancel or spread away from each other. These changes correspond to increases in EUV emission, as observed by TRACE, EIT, and CDS. This suggests that the plasma is temporarily heated along the filament spine. An idealized sequence of force-free models of this filament channel, based on plasma-supporting magnetic dips occurring in the windings of a very weakly twisted flux tube, naturally explains the evolution of its southern part as being due to changes in the topology of the coronal magnetic field as the photospheric flux concentrations evolve.     

Period variations in BZ Eridani

The O-C diagram of BZ Eri has been presented for the first time, and the period variations present in the system have been analysed. In all, eight period decreases and eight period increases are noticed. Of these, four period decreases and seven period increases are appreciable. The strongest period changes are noticed in the interval 1960 to 1962. The total period change in different portions of the O-C diagram ranges from 1.17×10^–3 d to 3.96×10^–6 d. The trend of the period variation appears to have reversed around the year 1980.     

Precursor heating and acceleration by Langmuir waves: The type II Supernova case

The effect of shock wave propagation is investigated with respect to precursor heating and acceleration, upstream, with the aim of explaining Supernova (SN) observations.A model is presented, where two different sources of Langmuir waves produce upstream heating and acceleration: (1) Langmuir waves excited by resonance beam particles, that are accelerated through the shock front by Bell's mechanism; and (2) Langmuir waves, created in the post-shock turbulent zone.The most important processes considered in the calculations are: (1) the heating efficiency of beam particles of different velocity; (2) Bell's acceleration efficiency; (3) the spectrum of Langmuir waves created in a turbulent regime; (4) the effects of density, and of the density gradient in the medium, where the shock propagates.The calculations are applied to type II SN. The results show that temperatures of 10⁵–10⁶ K, obtained in the preshock region, can explain P-Cygni observed line profiles. Moreover, accelerations of the plasma in front of the shock up tov10⁸ cm s^–1 by momentum exchange, are in good agreement with observations.Partially supported by Conselho Nacional de Desenvolvimento Cientifico e Technológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).     

Einstein-Gleichungen mit Zusatztermen 4. Ordnung und Raum-Zeit-Modelle vom Bianchi-Typ I

In the vacuum case, Einstein's equations generalized by additive terms containing derivatives of the metric up to the 4th order are applied to cosmological Bianchi-type I model space-times.