9,848 research outputs found
On the Clustering of GRBs on the Sky
The two-point correlation of the 4th (current) BATSE catalog (2494 objects)
is calculated. It is shown to be consistent with zero at nearly all angular
scales of interest. Assuming that GRBs trace the large scale structure in the
universe we calculate the angular correlation function for the standard CDM
(sCDM) model. It is shown to be at if the
BATSE catalog is assumed to be a volume-limited sample up to .
Combined with the error analysis on the BATSE catalog this suggests that nearly
GRBs will be needed to make a positive detection of the two-point
angular correlation function at this angular scale.Comment: 5 pages, Latex with aipproc.sty, incl. 1 ps-Fig., Proc. of the 5th
Huntsville Gamma Ray Burst Symposium, Oct. 1999, ed. R.M. Kippen, AI
The Characteristics of Magnetic CVs in the Period Gap
We have observed several magnetic cataclysmic variables located in the range
between 2 and 3 hours, known as the period gap. This work was prompted by the
recent discovery of RX J1554.2+2721. It has 2.54 hours orbital period and shows
almost pure cyclotron continuum in a low luminosity state, similar to
HS1023+3900,
HS0922+1333 and RBS206. These are low accretion rate polars (LARPs) known to
have mass transfer rates of order of a few 10^-13Msun/year.
The aim of the study was to find out, if magnetic systems filling the period
gap are in any way different from their counterparts outside that range of
periods. The only significant difference we encounter, is much higher number of
asynchronous magnetic systems to-wards longer periods than below the gap.Comment: 7 pages, 7 figures, To appear in `Magnetic Cataclysmic Variables',
IAU Col. 190 (Cape Town), eds. M. Cropper & S. Vrielman
Numerical analysis of nanostructures for enhanced light extraction from OLEDs
Nanostructures, like periodic arrays of scatters or low-index gratings, are
used to improve the light outcoupling from organic light-emitting diodes
(OLED). In order to optimize geometrical and material properties of such
structures, simulations of the outcoupling process are very helpful. The finite
element method is best suited for an accurate discretization of the geometry
and the singular-like field profile within the structured layer and the
emitting layer. However, a finite element simulation of the overall OLED stack
is often beyond available computer resources. The main focus of this paper is
the simulation of a single dipole source embedded into a twofold infinitely
periodic OLED structure. To overcome the numerical burden we apply the Floquet
transform, so that the computational domain reduces to the unit cell. The
relevant outcoupling data are then gained by inverse Flouqet transforming. This
step requires a careful numerical treatment as reported in this paper
Fermi Condensates
Ultracold atomic gases have proven to be remarkable model systems for
exploring quantum mechanical phenomena. Experimental work on gases of fermionic
atoms in particular has seen large recent progress including the attainment of
so-called Fermi condensates. In this article we will discuss this recent
development and the unique control over interparticle interactions that made it
possible.Comment: Proceedings of ICAP-2004 (Rio de Janeiro). Review of Potassium
experiment at JILA, Boulder, C
Lifetime of molecule-atom mixtures near a Feshbach resonance in 40K
We report a dramatic magnetic field dependence in the lifetime of trapped,
ultracold diatomic molecules created through an s-wave Feshbach resonance in
40K. The molecule lifetime increases from less than 1 ms away from the Feshbach
resonance to greater than 100 ms near resonance. We also have measured the
trapped atom lifetime as a function of magnetic field near the Feshbach
resonance; we find that the atom loss is more pronounced on the side of the
resonance containing the molecular bound state
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