Solitonic generation of five-dimensional black ring solution

Using the solitonic solution-generating technique we rederived the one-rotational five-dimensional black ring solution found by Emparan and Reall. The seed solution is not the Minkowski metric, which is the seed of $S^2$-rotating black ring. The obtained solution has more parameters than the Emparan and Reall's $S^1$-rotating black ring. We found the conditions of parameters to reduce the solution to the $S^1$-rotating black ring. In addition we examined the relation between the expressions of the metric in the prolate-spheroidal coordinates and in the canonical coordinates.Comment: 5 pages, 4 figures ; accepted version, several details are remove

Gravitational Radiation from a Naked Singularity -- Odd-Parity Perturbation --

It has been suggested that a naked singularity may be a good candidate for a strong gravitational wave burster. The naked singularity occurs in the generic collapse of an inhomogeneous dust ball. We study odd-parity mode of gravitational waves from a naked singularity of the Lema\^{\i}tre-Tolman-Bondi space-time. The wave equation for gravitational waves are solved by numerical integration using the single null coordinate. The result is that the naked singularity is not a strong source of the odd-parity gravitational radiation although the metric perturbation grows in the central region. Therefore, the Cauchy horizon in this space-time would be marginally stable against odd-parity perturbations.Comment: 14 pages, 7 figures, to be published in Prog. Theor. Phys. Final version, with minor changes. Reference 13 adde

Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator

We have investigated the dielectric response in an antiferromagnetic dimer-Mott insulator beta'-(BEDT-TTF)2ICl2 with square lattice, compared to a spin liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3. Temperature dependence of the dielectric constant shows a peak structure obeying Curie-Weiss law with strong frequency dependence. We found an anisotropic ferroelectricity by pyrocurrent measurements, which suggests the charge disproportionation in a dimer. The ferroelectric actual charge freezing temperature is related to the antiferromagnetic interaction, which is expected to the charge-spin coupled degrees of freedom in the system.Comment: 5 pages, 4 figures, to be published in Phys. Rev.

Gravitational Radiation from a Naked Singularity. II - Even-Parity Perturbation -

A naked singularity occurs in the generic collapse of an inhomogeneous dust ball. We study the even-parity mode of gravitational waves from a naked singularity of the Lema\^{\i}tre-Tolman-Bondi spacetime. The wave equations for gravitational waves are solved by numerical integration using the single null coordinate. The result implies that the metric perturbation grows when it approaches the Cauchy horizon and diverges there, although the naked singularity is not a strong source of even-parity gravitational radiation. Therefore, the Cauchy horizon in this spacetime should be unstable with respect to linear even-parity perturbations.Comment: 16 pages, 5 figures, errors and typos corrected, final versio

Partial and macroscopic phase coherences in underdoped Bi2{}_{2}Sr2{}_{2}CaCu2{}_{2}O8+δ{}_{8+{\delta}} thin film

A combined study with use of time-domain pump-probe spectroscopy and time-domain terahertz transmission spectroscopy have been carried out on an underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+{\delta}}$ thin film. It was observed that the low energy multi-excitation states were decomposed into superconducting gap and pseudogap. The pseudogap locally opens below $T^*{\simeq}210$ K simultaneously with the appearance of the high-frequency partial pairs around 1.3 THz. With decreasing temperature, the number of the local domains with the partial phase coherence increased and saturated near 100 K, and the macroscopic superconductivity appeared below 76 K through the superconductivity fluctuation state below 100 K. These experimental results indicate that the pseudogap makes an important role for realization of the superconductivity as a precursor to switch from the partial to the macroscopic phase coherence.Comment: Revtex4, 4 pages, 4 figure

Naked Singularity Explosion

It is known that the gravitational collapse of a dust ball results in naked singularity formation from an initial density profile which is physically reasonable. In this paper, we show that explosive radiation is emitted during the formation process of the naked singularity.Comment: 6 pages, 3 figures, Accepted for Publication in Phys. Rev. D as a Rapid Communicatio