Seismic Crack Investigation in an Earth Dam by Centrifugal Loading Test

There are many Earth-fill dams in Japan, which are mostly used for irrigation use. Most of these dams in Japan were constructed by experience over 100 years ago. There are so many irrigation dams, which suffered earthquake damage in the past. Due to the damages, the cracks at the crest in the dam-axis direction have been reported in many cases. For the rock-fill dam recently constructed, the crack on the crest in the dam-axis direction has also been found in the case of a large earthquake. The mechanism of such a crack has not been discussed well. In this study, to clarify the mechanism of a crack in the dam-axis direction, a centrifugal loading test was applied to the dam with a 50 G gravity field. As a result, the critical level of strain was observed at the crest of the model, and it was found that the horizontal displacement at the upper part of the dam was excessive. It can be concluded from the study that the seismic cracks in the dam-axis direction occurred due to the excessive tensile stress, which was not considered in the design process

Superradiant scattering of electromagnetic waves emitted from disk around Kerr black holes

We study electromagnetic perturbations around a Kerr black hole surrounded by a thin disk on the equatorial plane. Our main purpose is to reveal the black hole superradiance of electromagnetic waves emitted from the disk surface. The outgoing Kerr-Schild field is used to describe the disk emission, and the superradiant scattering is represented by a vacuum wave field which is added to satisfy the ingoing condition on the horizon. The formula to calculate the energy flux on the disk surface is presented, and the energy transport in the disk-black hole system is investigated. Within the low-frequency approximation we find that the energy extracted from the rotating black hole is mainly transported back to the disk, and the energy spectrum of electromagnetic waves observed at infinity is also discussed.Comment: 15 pages, 2 figures, accepted for publication in Physical Review

Gain tuning and fidelity in continuous variable quantum teleportation

The fidelity of continuous variable teleportation can be optimized by changing the gain in the modulation of the output field. We discuss the gain dependence of fidelity for coherent, vacuum and one photon inputs and propose optimal gain tuning strategies for corresponding input selections.Comment: 23 pages, 10 figure

Information extraction and quantum state distortions in continuous variable quantum teleportation

We analyze the loss of fidelity in continuous variable teleportation due to non-maximal entanglement. It is shown that the quantum state distortions correspond to the measurement back-action of a field amplitude measurement. Results for coherent states and for photon number states are presented.Comment: 4 pages Latex, contribution to the proceedings of the ISQM'01 conference held August 27th to 30th in Toky

Fidelity and information in the quantum teleportation of continuous variables

Ideally, quantum teleportation should transfer a quantum state without distortion and without providing any information about that state. However, quantum teleportation of continuous electromagnetic field variables introduces additional noise, limiting the fidelity of the quantum state transfer. In this article, the operator describing the quantum state transfer is derived. The transfer operator modifies the probability amplitudes of the quantum state in a shifted photon number base by enhancing low photon numbers and suppressing high photon numbers. This modification of the statistical weight corresponds to a measurement of finite resolution performed on the original quantum state. The limited fidelity of quantum teleportation is thus shown to be a direct consequence of the information obtained in the measurement.Comment: 10 pages, including one figure, minor clarifications and added referenc