Is the age problem resolved?

The cosmological, astrophysical, and nucleocosmochronological methods for estimating the age of the universe and the corresponding uncertainties are comparatively studied in the present paper. We are led to the conclusion that the new measurements of cosmological parameters, and the recent estimates of the age of globular clusters have led to the gradual disappearance of the age problem from the arena of modern cosmology.     

Wormhole deformation of the Reissner-Nordstr?m spacetime

A radial deformation of the Reissner-Nordstr?m metric which leads to the appearance of charged, traversable wormholes is investigated. It is shown that the resulting wormholes are not covered by event horizons and physical signals can travel between the two parallel universes either way across the wormhole. The status of energy conditions and the classification of geodesics are also discussed in details.     

Photometric observation and light curve analysis of binary system ER-Orionis

Photometric observations of the over-contact binary ER ORI were performed during November 2007 and February to April 2008 with the 51 cm telescope of Biruni Observatory of Shiraz University in U, B and V filters (Johnson system) and an RCA 4509 photomultiplier. We used these data to obtain the light curves and calculate the newtimes of minimum light in each filter and plot the O-C diagram of ER ORI. Using theWilson’s computer code with the help of an auxiliary computer program to improve the optimizations, the light curve analyses were carried out to find out the photometric elements of the system.     

(n+1)-dimensional Lorentzian wormholes in an expanding cosmological background

We discuss (n+1)-dimensional dynamical wormholes in an evolving cosmological background with a throat expanding with time. These solutions are examined in the general relativity framework. A linear relation between diagonal elements of an anisotropic energy-momentum tensor is used to obtain the solutions. The energy-momentum tensor elements approach the vacuum case when we are far from the central object for one class of solutions. Finally, we discuss the energy-momentum tensor which supports this geometry, taking into account the energy conditions.     

A class of cosmological solutions of Brans-Dicke theory with cosmological constant

We present a class of exact cosmological solutions of Brans-Dicke (B-D) equations with cosmological constant in flat Robertson-Walker metric. These solutions are based on the relation øR ⁿ= constant between the B-D field and the scale factor of the universe. This relation turns out to be consistent with the equation of statep =m for the cosmic matter, provided thatn andm are suitably related to each other. Several special cases and asymptotic solutions are derived and discussed.     

Physical properties of charged Kaluza-Klein black holes

In this paper, we consider an exact vacuum solution of the Kaluza-Klein (KK) theory, which describes nonrotating KK black holes. We investigate general properties of geodesic motion in the space-time and calculate the effective potential for null geodesics. The thermodynamical quantities as well as the gravitational lensing of the solution is calculated. We illustrate that the Carter-Penrose diagram for different parameter values resembles the Schwarzschild-like, naked and charged solutions.     

Photometric Observation And Period Study Of Go Cygni

Photometric observations of GO Cyg were performed during July–October 2002, in B and V filters (Johnson system). Using the Wilson's computer codes, the light curve analysis were carried out to find the photometric elements of the system. The O-C diagram which is based on the observed times of minima as well as those found in the literature, suggests a negative rate of period variation (i.e. ) for the system.     

Some exact geometries for asymptotically De Sitter spacetimes

Spherical, time-dependent geometrical structures in an inflationary RW background are derived from the Einstein equations, using a constraint on the energy-momentum tensor which is an extension of the one expected for inflation. The possibility of dynamical wormholes and other spherical structures are explored in the framework of the solutions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photometric Observations and Apsidal Motion Study of V1143 Cyg

Photometric observations of the eccentric eclipsing binary V1143 Cyg were performed during Aug.–Sep. 2000 and July 2002, in Johnson B and V bands. The analysis of both light curves was made separately using the 1998 version of Wilson’s LC code. In order to find a new observed rate of apsidal motion, we followed the procedure described by Guinan and Maloney (1985). A new observed rate of apsidal motion of 3^∘.72/100 yr was computed, which is close to the one reported earlier by Khaliullin (1983), Gimenez and Margrave (1985), and Burns et al. (1996).