Collapsing open isotropic universe generated by nonminimally coupled scalar field

We investigated the behavior of an open isotropic universe generated by a scalar field which couples with background curvature nonminimally with the coupling constant $\xi$. In particular we focus on the situation where the initial value for the scalar field $\phi_{\rm in}$ is greater than the critical value ${\hat \phi}_c$=${m_p}/{\sqrt{8\pi\xi(1-6\xi)}}$. The behavior is similar to an open de Sitter universe with $k=-1$ with a negative cosmological constant $\Lambda <0$. It is found that the universe will collapse eventually to a singularity and thus has a finite extent in time in the future. Furthermore, there are some cases which shows a rebouncing behavior before the final collapse.Comment: 8 pages, 3 ps files, submitted to Phys.Lett.

New derivation of a third post-Newtonian equation of motion for relativistic compact binaries without ambiguity

A third post-Newtonian (3 PN) equation of motion for an inspiralling binary consisting of two spherical compact stars with strong internal gravity is derived under harmonic coordinate condition using the strong field point particle limit. The equation of motion is complete in a sense that it is Lorentz invariant in the post-Newtonian perturbative sense, admits conserved energy of the orbital motion, and is unambiguous, that is, with no undetermined coefficient. In this paper, we show explicit expressions of the 3 PN equation of motion and an energy of the binary orbital motion in case of the circular orbit (neglecting the 2.5 PN radiation reaction effect) and in the center of the mass frame. It is argued that the 3 PN equation of motion we obtained is physically unambiguous. Full details will be reported elsewhere.Comment: 6 pages, No figure, Revised version,clarity improved, accepted for publication in Phys. Rev. D.(R

On a Growing Transverse Mode as a Post-Newtonian Effect in the Large-Scale Structure Formation

We point out the existence of a new type of growing transverse mode in the gravitational instability. This appears as a post-Newtonian effect to Newtonian dynamics. We demonstrate this existence by formulating the Lagrangian perturbation theory in the framework of the cosmological post-Newtonian approximation in general relativity. Such post-Newtonian order effects might produce characteristic appearances of large-scale structure formation, for example, through the observation of anisotropy of the cosmic microwave background radiation (CMB).Comment: 12 pages, no figure. To be published in Prog. Theor. Phys.(August issue

Possible measurement of Quintessence and density parameter using strong gravitational lensing events

We propose a possible measurement of the time variability of the vacuum energy using strong gravitational lensing events. As an example we take an Einstein cross lens HST 14176+5226 and demonstrate that the measurement of the velocity dispersion with the accuracy of $\pm$ 5 km/sec will have a chance to determine the time dependence of the vacuum energy as well as the density parameter with the accuracy of order 0.1 if one fixes the lens model.Comment: 5 pages, 1 figure, accepted for publication in Progress of Theoretical Physic