Spatial Distribution of Energetic Electrons in the Geomagnetic Tail

Spatial distribution of energetic electrons in geomagnetic tai

Universal Behavior in Large-scale Aggregation of Independent Noisy Observations

Aggregation of noisy observations involves a difficult tradeoff between observation quality, which can be increased by increasing the number of observations, and aggregation quality which decreases if the number of observations is too large. We clarify this behavior for a protypical system in which arbitrarily large numbers of observations exceeding the system capacity can be aggregated using lossy data compression. We show the existence of a scaling relation between the collective error and the system capacity, and show that large scale lossy aggregation can outperform lossless aggregation above a critical level of observation noise. Further, we show that universal results for scaling and critical value of noise which are independent of system capacity can be obtained by considering asymptotic behavior when the system capacity increases toward infinity.Comment: 10 pages, 3 figure

LSND, SN1987A, and CPT Violation

We point out that neutrino events observed at Kamiokande and IMB from SN1987A disfavor the neutrino oscillation parameters preferred by the LSND experiment. For $\Delta m^2 > 0$ (the light side), the electron neutrinos from the neutronization burst would be lost, while the first event at Kamiokande is quite likely to be due to an electron neutrino. For $\Delta m^2 < 0$ (the dark side), the average energy of the dominantly $\bar{\nu}_e$ events is already lower than the theoretical expectations, which would get aggravated by a complete conversion from $\bar{\nu}_\mu$ to $\bar{\nu}_e$. If taken seriously, the LSND data are disfavored independent of the existence of a sterile neutrino. A possible remedy is CPT violation, which allows different mass spectra for neutrinos and anti-neutrinos and hence can accommodate atmospheric, solar and LSND data without a sterile neutrino. If this is the case, Mini-BooNE must run in $\bar{\nu}$ rather than the planned $\nu$ mode to test the LSND signal. We speculate on a possible origin of CPT violation.Comment: 4 pages, REVTEX. Discussions on multi-flavor mixing adde

A Geometrical Relationship between Broad-Line Clouds and an Accretion Disk around Active Galactic Nuclei

Recent hard X-ray spectroscopy of active galactic nuclei has strongly suggested that double-peaked, very broad Fe K emission arises from an accretion disk around the central engine. Model fitting of the observed Fe K emission line profile makes it possible to estimate a probable inclination angle of the accretion disk. In order to study the geometrical relationship between the accretion disk and broad emission-line regions (BLRs), we investigate the correlation between the inclination angle of the accretion disk and the velocity width of BLRs for 18 type-1 Seyfert galaxies. We found that there may be a negative correlation between them, i.e., Seyfert nuclei with a more face-on accretion disk tend to have larger BLR velocity widths, suggesting that the BLRs are not coplanar with respect to the accretion disk. The most probable interpretation may be that the BLRs arise from outer parts ({\it r} $\sim$ 0.01 pc) of a warped accretion disk illuminated by the central engine.Comment: 11 pages, 3 figures; accepted for Publications of the Astronomical Society of Japa

Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04-012502.2

We obtained near-infrared spectroscopy of the z=5.74 QSO, SDSSp J104433.04-012 502.2 with the Infrared Camera and Spectrograph of the Subaru telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr for the current Lambda-dominated cosmology. We found a similar strength of the Fe II (3000-3500 A) emission lines in SDSSp J104433.04-012502.2 as in low redshift QSOs. This is the highest redshift detection of iron. We subtracted a power-law continuum from the spectrum and fitted model Fe II emission and Balmer continuum. The rest equivalent width of Fe II (3000-3500 A) is ~30 A which is similar to those of low redshift QSOs measured by the same manner. The chemical enrichment models that assume the life time of the progenitor of SNe Ia is longer than 1 Gyr predict that weaker Fe II emission than low red shift. However, none of the observed high redshift (z > 3) QSOs show a systematic dec rease of Fe II emission compared with low redshift QSOs. This may due to a shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood. Another reason of strong Fe II emission at z=5.74 may be longer cosmological age due to smaller Omega_M.Comment: 5 pages, 3 figure

Stress concentration in the vicinity of a hole defect under conditions of Hertzian contact

Two dimensional photoelastic stress analyses were conducted for epoxy resin models containing a hole defect under the conditions of Hertzian contact. Stress concentrations around the defect were determined as a function of several parameters. The effect of tangential traction on the stress concentration was also determined. Sharp stress concentrations occur in the vicinity of both the left and the right side of the hole. The stress concentration becomes more distinct the larger the hole diameter and the smaller distance between the hole and the contact surface. The stress concentration is greatest when the disk imposing a normal load is located at the contact surface directly over the hole. The magnitude and the location of stress concentration varies with the distance between the Hertzian contact area and the hole. The area involved in a process of rolling contact fatigue is confined to a shallow region at both sides of the hole. It was found that the effect of tangential traction is comparatively small on the stress concentration around the hole