Pseudo-Hermitian approach to Goldstone’s theorem in non-Abelian non-Hermitian quantum field theories

We generalize previous studies on the extension of Goldstone’s theorem from Hermitian to non-Hermitian quantum field theories with Abelian symmetries to theories possessing a glocal non-Abelian symmetry. We present a detailed analysis for a non-Hermitian field theory with two complex two component scalar fields possessing an SU(2) symmetry and indicate how our findings extend to the general case. In the PT-symmetric regime (parity and time-reversal) and at the standard exceptional point the Goldstone theorem is shown to apply, although different identification procedures need to be employed. At the zero exceptional points the Goldstone boson can not be identified. Comparing our approach, based on the pseudo-Hermiticity of the model, to an alternative approach that utilizes surface terms to achieve compatibility for the non-Hermitian system, we find that the explicit forms of the Goldstone boson fields are different

Spin-Glass-like Transition and Hall Resistivity of Y2-xBixIr2O7

Various physical properties of the pyrochlore oxide Y2-xBixIr2O7 have been studied. The magnetizations M measured under the conditions of the zero-field-cooling(ZFC) and the field-cooling(FC) have different values below the temperature T=TG. The anomalous T-dependence of the electrical resistivities r and the thermoelectric powers S observed at around TG indicates that the behavior of the magnetization is due to the transition to the state with the spin freezing. In this spin-frozen state, the Hall resistivities rH measured with the ZFC and FC conditions are found to have different values, too, in the low temperature phase (T<TG). Possible mechanisms which induce such the hysteretic behavior are discussed.Comment: 9 pages, 7 figures, J. Phys. Soc. Jpn. 72 (2003) No.

Emergence of Larkin-Ovchinnikov-type superconducting state in a voltage-driven superconductor

We theoretically investigate a voltage-biased normal metal-superconductor-normal metal (N-S-N) junction. Using the nonequilibrium Green's function technique, we derive a quantum kinetic equation, to determine the superconducting order parameter self-consistently. The derived equation is an integral-differential equation with memory effects. We solve this equation by converting it into a system of ordinary differential equations with the use of a pole expansion of the Fermi-Dirac function. When the applied voltage exceeds the critical value, the superconductor switches to the normal state. We find that when the voltage is decreased from the normal phase, the system relaxes to a Larkin-Ovchinnikov (LO)-type inhomogeneous superconducting state, even in the absence of a magnetic Zeeman field. We point out that the emergence of the LO-type state can be attributed to the nonequilibrium energy distribution of electrons due to the bias voltage. We also point out that the system exhibits bistability, which leads to hysteresis in the voltage-current characteristic of the N-S-N junction.Comment: 20 pages, 14 figure

High sensitive X-ray films to detect electron showers in 100 GeV region

Nonscreen type X-ray films were used in emulsion chamber experiments to detect high energy showers in cosmic rays. Ranges of the detection threshold is from about 1 to 2 TeV depending on the exposure conditions. Different types of X-ray films and sheets i.e. high sensitive screen type X-ray films and luminescence sheets were tested. The threshold of the shower detection is found to be about 200 GeV, which is much lower than that of nonscreen type X-ray films. These films are useful to detect showers in the medium energy range, a few hundred GeV, of the cosmic ray electrons

Convertible source system of thermal neutron and X-ray at Hokkaido University electron linac facility

The convertible source system for the neutron and the X-ray imagings was installed in the 45MeV electron linear accelerator facility at Hokkaido University. The source system is very useful for a complementary imaging. The imaging measurements for a sample were performed with both beams by using a vacuum tube type image intensifier. The enhanced contrast was obtained from the dataset of the radiograms measured with the neutron and X-ray beams

High energy electrons beyond 100 GEV observed by emulsion chamber

Much efforts have been expended to observe the spectrum of electrons in the high energy region with large area emulsion chambers exposed at balloon altitudes, and now 15 electrons beyond 1 TeV have been observed. The observed integral flux at 1 TeV is (3.24 + or - 0.87)x10(-5)/sq m sec sr. The statistics of the data around a few hundred GeV are also improving by using new shower detecting films of high sensitivity. The astrophysical significance of the observed spectrum are discussed for the propagation of electrons based on the leaky box and the nested leaky box model