arXiv subjects

T. Takayanagi

Publications and source records attributed to T. Takayanagi.

6 recordsLinked to original sources

arXiv2026

A diagnostic system of 5.7 keV muon beam for muon accelerator

Realization of a low-emittance muon beam through the acceleration of keV-scale muons requires the injection of a suitably matched beam into an accelerator, since beam mismatch can lead to emittance growth and reduced acceleration efficiency. In one such scheme, muons are first thermalized to room temperature and then injected into a linear accelerator. Non-destructive diagnostics are challenging because of the low energy and low intensity. We developed a compact low-energy muon diagnostic system compatible with the accelerator under construction at J-PARC. The system is designed to evaluate beam conditions required for precise tuning prior to acceleration. Commissioning with low-energy muon sources shows the system's capability to identify low-energy muon signals and measure beam profiles.

physics.acc-ph↗

arXiv2001

Out-of-plane dielectric constant and insulator-superconductor transition in Bi_2Sr_2Dy_{1-x}Er_xCu_2O_8 single crystals

The out-of-plane dielectric constant of the parent insulator of the high-temperature superconductor Bi_2Sr_2(Dy,Er)Cu_2O_8 was measured and analysed from 80 to 300 K in the frequency range of 10^6-10^9 Hz. All the samples were found to show a fairly large value of 10-60, implying some kind of charge inhomogeneity in the CuO_2 plane. Considering that the superconducting sample Bi_2Sr_2(Ca,Pr)Cu_2O_8 also shows a similar dielectric constant, the charge inhomogeneity plays an important role in the insulator-superconductor transition.

cond-mat.str-el↗

arXiv2000

Tachyon Condensation on Noncommutative Torus

We discuss noncommutative solitons on a noncommutative torus and their application to tachyon condensation. In the large B limit, they can be exactly described by the Powers-Rieffel projection operators known in the mathematical literature. The resulting soliton spectrum is consistent with T-duality and is surprisingly interesting. It is shown that an instability arises for any D-branes, leading to the decay into many smaller D-branes. This phenomenon is the consequence of the fact that K-homology for type II von Neumann factor is labeled by R.

hep-th↗

arXiv1999

Anomalous charge transport of the parent antiferromagnet Bi2Sr2RCu2O8

The resistivity and the thermopower for Bi2Sr2Ca{1-x}RxCu2O8 single crystals are measured and analyzed with a special interest in the parent antiferromagnet insulators. Above room temperature, the parent insulators show an electric conduction confined in the CuO2 plane and a decreasing thermopower with temperature, which are very similar to those for high-$T_c$ cuprates. These data strongly suggest that essential anomalies of high-Tc cuprates inheres in the parent insulators.

cond-mat.supr-con↗

arXiv1999

Anisotropic dielectric constant of the parent antiferromagnet Bi2Sr2MCu2O8 (M=Dy, Y and Er) single crystals

The anisotropic dielectric constants of the parent antiferromagnet Bi2Sr2MCu2O8 (M=Dy, Y and Er) single crystals were measured from 80 to 300 K. The in-plane dielectric constant is found to be very huge (10^4-10^5). This suggests a remnant of the Fremi surface of the parent antiferromagnet. The out-of-plane dielectric constant is 50-200, which is three orders of magnitude smaller than the in-plane one. A significant anomaly is that a similar out-of-plane dielectric constant is observed in superconducting samples.

cond-mat.supr-con↗

arXiv1999

Anisotropic resistivity of the antiferromagnetic insulator Bi_2Sr_2ErCu_2O_8

Anisotropic resistivities of Bi_2Sr_2Ca_{1-x}Er_xCu_2O_8 single crystals were measured and analyzed from 4.2 to 500 K with special interest in the parent antiferromagnetic insulator of x=1.0. Although the resistivity is semiconducting along both the in- and out-of-plane directions, the temperature dependence is found to be significantly different. As a result, the resistivity ratio for x=1.0 takes a broad maximum near room temperature. The electric conduction in parent antiferromagnetic insulators is different from other semiconductors, and is as unconventional as that in high-temperature superconductors.

cond-mat.supr-con↗