3,809 research outputs found
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 (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 (the dark
side), the average energy of the dominantly events is already
lower than the theoretical expectations, which would get aggravated by a
complete conversion from to . 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 rather than the planned 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} 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
- …