31880865
Holomorphic wave function of the Universe.
The quantum behavior of the vacuum Bianchi type-IX universe with the cosmological constant is investigated in terms of the Ashtekar variables. An exact solution to the quantum Hamiltonian constraint in the holomorphic representation is given. This solution reduces to the Hartle-Hawking wave function in the spatially isotropic sector and extends in the triad representation to the classically forbidden region where the determinant of the spatial metric becomes negative. The analysis of the quantum Robertson-Walker universe indicates that if the superspace is extended to such a classically forbidden region, the holomorphic representation picks up some restricted class of solutions in general. This observation leads to a new ansatz on the boundary condition of the Universe. In particular, the behavior of the Lorentzian and Euclidean WKB orbits corresponding to the solution suggests a new picture on the semiclassical behavior of the quantum Universe: that the Universe is created from an ensemble of Euclidean mother spacetimes. Further it is pointed out that the solution is a restriction to the spatially homogeneous sector of an almost exact solution to all the quantum constraints in the holomorphic representation for generic vacuum spacetime with the cosmological constant. The latter generic solution has a WKB structure formore » which the phase is proportional to the Chern-Simons functional.« less
15797280
What happens when the inflaton stops during inflation
The spectrum of adiabatic density perturbation generated during inflation is studied in the case the time derivative of an inflation-driving scalar field (inflaton) vanishes at some time during inflation. It is shown that the nondecaying mode of perturbation has a finite value even in this case and that its amplitude is given by the standard formula with the time derivation of the scalar field replaced by the potential gradient using the slow-roll equation.
123714634
Inevitability of a Naked Singularity Associated with the Black Hole Evaporation
119520080
Influence of Cooling Flows and Galactic Motion on the Iron Distribution in Clusters of Galaxies
Iron abundance distribution is now known for 12 clusters of galaxies. For some clusters (e.g. Centaurus) the observed abundance increases toward the cluster center, while for the others (e.g. Coma and Hydra-A) no significant inhomogeneity was observed. In order to understand this difference, we investigate the influence of cooling flow and turbulence produced by galactic motion on the iron abundance distribution by simple spherical models. We show that the cooling flow has a significant effect to flatten the iron abundance distribution if the flow velocity is sufficiently large. Further, by applying our analysis to the above clusters we show that we can give a systematic account for the observed variety of the iron abundance distribution qualitatively.
16810865
Stability of Higher-Dimensional Schwarzschild Black Holes
We investigate the classical stability of higher-dimensional Schwarzschild black holes with respect to linear perturbations in the framework of a gauge-invariant formalism for gravitational perturbations of maximally symmetric black holes. This formalism was recently developed by the present authors. The perturbations are classified into three types, those of tensor, vector and scalar modes, according to their tensorial behaviour on the spherical section of the background metric. The vector- and scalar-type modes correspond, respectively, to the axial and polar modes in the four-dimensional case. We show that for each mode of the perturbations, the spatial derivative part of the master equation is a positive, self-adjoint operator in the L 2 -Hilbert space, and hence that the master equation for each type of perturbation has no normalisable negative modes that would correspond to unstable solutions. In the same Schwarzschild background, we also analyse static perturbations of the scalar mode and show that there exists no static perturbation that is regular everywhere outside the event horizon and is well behaved at the spatial infinity. This confirms the uniqueness of the higher-dimensional spherically symmetric, static vacuum black hole, within the perturbation framework. Our strategy for treating the stability problem is also applicable to other higherdimensional maximally symmetric black holes with a non-vanishing cosmological constant. We show that all possible types of maximally symmetric black holes (including the higherdimensional Schwarzschild-de Sitter and Schwarzschild-anti-de Sitter black holes) are stable with respect to tensor and vector perturbations.
15822423
Superradiance and Instability of Black Holes
The stability of black holes has a crucial importance when we study their formation and fate in Nature. It also has an intimate relation with the cosmic censorship hypothesis. For these reasons, this problem has been studied for a long time, and uniqueness and perturbative stability were established for most asymptotically flat black holes in the four-dimensional Einstein-Maxwell system except for the KerrNewman black hole. 1),2) When we go beyond this classical system, we encounter various new situations. One such extension is to consider systems containing other types of matter. Very interesting examples are the Einstein-Skyrme system and the Einstein-Yang-Mills system. These systems have three families of static asymptotically flat spherically symmetric solutions; a soliton family, a hairy black hole family and the vacuum one. These all families of solutions were shown to be stable numerically for the EinsteinSkyrme system while for the EYM system, the colored black holes and the soliton solutions were shown to be unstable (see Ref. 3) for review). Hence, in the latter case, the uniqueness theorem holds practically. Another extension motivated by recent progresses in unified theories is to consider higher-dimensional black holes. In the static AF Einstein-Maxwell system, the uniqueness theorem still holds in higher dimensions. Further, in the vacuum case, the Schwarzschild-Tangherlini solution was shown to be stable 4) by using the extension of the Regge-Wheeler and Zerilli equations to higher dimensions, 5) although the stability of the charged static black hole was proved only for D = 5 analytically 6) and for 6 ≤ D ≤ 11 numerically. 7)
13245713
ERO R1 in CL0939+4713 field- Evidence for an S0-like galaxy at z ∼1.5 1
We report that an extremely red galaxy, ERO R1 with R − K = 7.4, identified in the field behind the cluster of galaxies A851 (=Cl 0939+4713) at z = 0.4 was shown to be a disk galaxy at z ∼ 1.5 with passively evolving stellar population, placing it the most distant S0-like galaxy ever observed. Its redshift was derived consistently from two independent methods; the photometric redshift method based on its V, R, F702W, i, J, H, and K ′ magnitudes using the HYPERZ code and the cross correlation method using its H-band spectrum and the optical spectra of local E/S0 galaxies. Although its colors are consistent both with an elliptical galaxy and an S0 galaxy at that redshift, its elongated shape indicates the S0-like nature of this galaxy and the measured exponential luminosity profile of this galaxy clearly shows its resemblance to the present day disk galaxies. The possible effect of the gravitational stretching due to the foreground cluster is not strong enough to explain its elongated shape and above all the lensing does not affect the shape of the luminosity profile. We, therefore, defy the interpretation of a lensed elliptical galaxy. The H-band spectrum does not show conspicuous redshifted Hα emission and the star forming activity in this galaxy, if any, appears to be very modest. The presence of such a galaxy with apparently dynamically relaxed disk system of stars at that high redshift poses a new constraint on theoretical models to explain the formation and evolution of galaxies. Subject headings: galaxies: clusters: individual(A851)—galaxies: ellipticals and lenticulars, cD—galaxies: evolution Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-