arXiv subjects
Publications and source records attributed to K. Maki.
Use is made of Onsager's hydrodynamic equation to derive the vibration spectrum of the vortex lattice in d-wave superconductor. In particular the rhombic lattice (i.e. the $45^\circ$ tilted square lattice) is found to be stable for $B>H_{cr}(t)$. Here $H_{cr}(t)$ denotes the critical field at which the vortex lattice transition takes place.
Prospects are examined for the detection of a slow decay of the lightest neutralino (or any other longlived particles) at the CERN LHC and at Very Large Hadron Collider (VLHC). We first point out that such hadron colliders will become the ``neutralino factory'' producing 10^6--10^9 neutralinos/yr, if gluinos and/or squarks actually exist below O(1) TeV. The lightest neutralino (\neu), usually assumed to be stable, will be unstable if lighter superparticles such as the gravitino (\gra) or axino (\axi) exist, or R-parity is not conserved. The decay signal would, however, be missed in usual collider experiments, particularly when the decay mostly occurs outside the detector. In order to search for such a slow decay of \neu, we propose a dedicated experiment where the collision products are dumped by a thick shield, which is followed by a long decay tunnel. The decay product of \neu can be detected by a detector located at the end of the tunnel. The slow arrival time and the large off angle (to the direction of the interaction point) of the decay product will provide a clear signature of slowly decaying \neu's. One can explore the decay length (cτ) in a wide range, i.e., 0.2 m to 1x10^5 km for \mneu=25 GeV and 1 m to 2 km for \mneu=200 GeV at the LHC. This corresponds to the range of the SUSY breaking scale \rtF=2x10^5 to 2x10^7 GeV in case of the \neu\toγ\gra decay predicted in gauge-mediated SUSY breaking models. At VLHC, one can extend the explorable range of \mneu up to 1000 GeV, and that of \rtF up to 1x10^8 GeV. In case of the \neu\toγ\axi decay, the Peccei- Quinn symmetry breaking scale F_a can be explored up to 5x10^11 GeV. The mass of the decaying particle can be determined by using the correlation between the energy and the arrival time of the decay product.
A full quantum-mechanical treatment of the Bogoliubov-de Gennes equation for a single vortex in a d-wave superconductor is presented. First, we find low-energy states extended in four diagonal directions, which have no counterpart in a vortex of s-wave superconductors. The four-fold symmetry is due to 'quantum effect', which is enhanced when $p_{F}ξ$ is small. Second, for $p_{F}ξ\sim 1$, a peak with a large energy gap $E_{0}\sim Δ$ is found in the density of states, which is due to the formation of the lowest bound states.
We calculate the solar-modulated energy spectra of cosmic-ray antiprotons ($\bar{p}$'s) from two candidate primary sources, i.e., evaporating primordial black holes and the annihilation of neutralino dark matter, as well as for the secondary $\bar{p}$'s produced by cosmic-ray interactions with interstellar gas. A large enhancement toward the solar minimum phase emerges in the low-energy flux of $\bar{p}$'s from the primary sources, whereas the flux of the secondary $\bar{p}$'s, falling steeply below 2 GeV, does not significantly vary. This enables us to conduct a very sensitive search for primary $\bar{p}$ components by precisely measuring the $\bar{p}$ spectrum, especially at low energies, throughout the forthcoming solar minimum phase.
Using the Bogoliubov-de Gennes equation, we study quasi-particle spectra around a single vortex in a d-wave superconductor, where a magnetic field is parallel to the c-axis. In the temperature region where the Ginzburg-Landau theory is valid, we find that the local density of states preserves a circular symmetry when the symmetry of the superconducting order parameter is {\it pure} d-wave. It, however, exhibits a four-fold symmetry when the mixing of a s-wave component occurs. A peak with a {\it large energy gap} is found in the local density of states at the center of the vortex, which corresponds to the lowest bound state. Our results are consistent with a recent scanning tunneling microscopy experiment in an YBa$_{2}$Cu$_{3}$O$_{7-δ}$ (YBCO) monocrystal. The breakdown of the Eilenberger theory in YBCO in particular and in the high-T$_{c}$ superconductors in generalis discussed.
We investigate low-energy cosmic-ray antiprotons ($\bar{p}$'s) arising from the fragmentation of quarks and gluons emitted from evaporating primordial black holes (PBHs). To calculate the local interstellar flux of these $\bar{p}$'s, their propagation in the Galaxy is described by a 3-D Monte Carlo simulation based on the diffusion model. This flux is used with recent observations to derive new upper limits on (i) the local PBH explosion rate ${\cal R}<1.7\times10^{-2}$ pc$^{-3}$yr$^{-1}$, (ii) the fraction of the Universe's mass going into PBHs with particular mass, and (iii) the average density of PBHs in the Universe.
We study theoretically the sound propagation in charge- and spin-density waves in the hydrodynamic regime. First, making use of the method of comoving frame, we construct the stress tensor appropriate for quasi-one dimensional systems within tight-binding approximation. Taking into account the screening effect of the long-range Coulomb interaction, we find that the increase of the sound velocity below the critical temperature is about two orders of magnitude less for longitudinal sound than for transverse one. It is shown that only the transverse sound wave with displacement vector parallel to the chain direction couples to the phason of the density wave, therefore we expect significant electromechanical effect only in this case.