Anomalous increase of solar anisotropy above 150GV in 1981-1983

An analysis was carried out of the observed data with Nagoya (surface). Misato (34mwe) and Sakashita (80mwe) multidirectional muon telescope, for the solar activity maximum period of 1978-1983. These data respond to primaries extending over the median rigidity range 60GV to 600GV. The observed amplitude at Sakashita station in 1981-1983 increased, especially in 1982; the amplitude is twice as large as that in 1978-1980, when those at Nagoya and Misato stations are nearly the same as those in 1978-1980. Uni-directional anisotropy is derived by the best fit method by assuming the flat rigidity spectrum with the upper cutoff rigidity Pu. The value of Pu obtained is 270GV in 1981-1983 and 150GV in 1978-1980

Sidereal anisotropies in the median rigidity range 60-600GV in 1978-1983

Observed sidereal variations are corrected for the influence of spurious variation by a method using the antisidereal diurnal variations produced from the same 2nd order anisotropy (Nagashima, et al., 1983). It is demonstrated that the corrected variations are a resultant product of two constituents of galactic origin: one is north-south (N-S) symmetric and the other is N-S asymmetric

Solar tri-diurnal variation of cosmic rays in a wide range of rigidity

Solar tri-diurnal variations of cosmic rays have been analyzed in a wide range of rigidity, using data from neutron monitors, and the surface and underground muon telescopes for the period 1978-1983. The rigidity spectrum of the anisotropy in space is assumed to be of power-exponential type as (P/gamma P sub o) to the gamma exp (gamma-P/P sub o). By means of the best-fit method between the observed and the expected variations, it is obtained that the spectrum has a peak at P (=gamma P sub o) approx = 90 GV, where gamma=approx 3.0 and P sub o approx. 30 GV. The phase in space of the tri-diurnal variation is also obtained as 7.0 hr (15 hr and 23 hr LT), which is quite different from that of approx. 1 hr. arising from the axisymmetric distribution of cosmic rays with respect to the IMF

Modeling Phase-resolved Observations of the Surfaces of Magnetic Neutron Stars

Recent observations by XMM-Newton detected rotational pulsations in the total brightness and spectrum of several neutron stars. To properly interpret the data, accurate modeling of neutron star emission is necessary. Detailed analysis of the shape and strength of the rotational variations allows a measurement of the surface composition and magnetic field, as well as constrains the nuclear equation of state. We discuss our models of the spectra and light curves of two of the most observed neutron stars, RX J1856.5-3754 and 1E 1207.4-5209, and discuss some implications of our results and the direction of future work.Comment: 5 pages, 6 figures; Proceedings of "40 Years of Pulsars", eds. C. Bassa, Z. Wang, A. Cumming, V. Kaspi, AIP, submitte

A History of Flips in Combinatorial Triangulations

Given two combinatorial triangulations, how many edge flips are necessary and sufficient to convert one into the other? This question has occupied researchers for over 75 years. We provide a comprehensive survey, including full proofs, of the various attempts to answer it.Comment: Added a paragraph referencing earlier work in the vertex-labelled setting that has implications for the unlabeled settin

Charge ordering in theta-(BEDT-TTF)_2 X materials

We investigate theoretically charge ordered states on the anisotropic triangular lattice characteristic of the theta-(BEDT-TTF)_2 X materials. Using exact diagonalization studies, we establish that the charge order (CO) pattern corresponds to a ``horizontal'' stripe structure, with ...1100... CO along the two directions with larger electron hopping (p-directions), and ...1010... CO along the third direction (c-direction). The CO is accompanied by co-operative bond dimerizations along all three directions in the highest spin state. In the lowest spin state bonds along the p-directions are tetramerized. Our theory explains the occurence of a charge-induced high temperature transition as well as a spin gap transition at lower temperature.Comment: 4 pages, 4 eps figures, uses jpsj2.cl

Radially Polarized, Half-Cycle, Attosecond Pulses from Laser Wakefields through Coherent Synchrotron Radiation

Attosecond bursts of coherent synchrotron-like radiation are found when driving ultrathin relativistic electron disks in a quasi-one-dimensional regime of wakefield acceleration, in which the laser waist is larger than the wake wavelength. The disks of overcritical density shrink radially due to the focusing wake fields, thus providing the transverse currents for the emission of an intense, radially polarized, half-cycle pulse of about 100 attoseconds in duration. The electromagnetic pulse first focuses to a peak intensity 10 times larger ($7\times10^{20}\rm W/cm^2$) than the driving pulse and then emerges as a conical beam. Saturation of the emission amplitudes is derived analytically and in agreement with particle-in-cell simulation. By making use of gas targets instead of solids to form the ultrathin disks, the new scheme allows for high repetition rate required for applications.Comment: 5 pages, 4 figure

Commensurate-Incommensurate transition in the melting process of the orbital ordering in Pr0.5Ca0.5MnO3: neutron diffraction study

The melting process of the orbital order in Pr0.5Ca0.5MnO3 single crystal has been studied in detail as a function of temperature by neutron diffraction. It is demonstrated that a commensurate-incommensurate (C-IC) transition of the orbital ordering takes place in a bulk sample, being consistent with the electron diffraction studies. The lattice structure and the transport properties go through drastic changes in the IC orbital ordering phase below the charge/orbital ordering temperature Tco/oo, indicating that the anomalies are intimately related to the partial disordering of the orbital order, unlike the consensus that it is related to the charge disordering process. For the same T range, partial disorder of the orbital ordering turns on the ferromagnetic spin fluctuations which were observed in a previous neutron scattering study.Comment: 5 pages, 2 figures, REVTeX, to be published in Phys. Rev.