551 research outputs found
One-Loop NMHV Amplitudes involving Gluinos and Scalars in N=4 Gauge Theory
We use Supersymmetric Ward Identities and quadruple cuts to generate n-pt
NMHV amplitudes involving gluinos and adjoint scalars from purely gluonic
amplitudes. We present a set of factors that can be used to generate one-loop
NMHV amplitudes involving gluinos or adjoint scalars in N=4 Super Yang-Mills
from the corresponding purely gluonic amplitude.Comment: 16 pages, JHEP versio
Discovery of a redshift 6.13 quasar in the UKIRT infrared deep sky survey
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO) DOI: 10.1051/0004-6361/200811161Optical and near-infrared (NIR) spectra are presented for ULAS J131911.29+095051.4 (hereafter ULAS J1319+0950), a new redshift z = 6.127 0.004 quasar discovered in the Third Data Release (DR3) of the UKIRT Infrared Deep Sky Survey (UKIDSS). The source has = 19.10 0.03, corresponding to = -27.12, which is comparable to the absolute magnitudes of the z 6 quasars discovered in the Sloan Digital Sky Survey (SDSS). ULAS J1319+0950 was, in fact, registered by SDSS as a faint source with = 20.13 0.12, just below the signal-to-noise ratio limit of the SDSS high-redshift quasar survey. The faint z-band magnitude is a consequence of the weak Ly /N V emission line, which has a rest-frame equivalent width of ~20Å and provides only a small boost to the z-band flux. Nevertheless, there is no evidence of a significant new population of high-redshift quasars with weak emission lines from this UKIDSS-based search. The Ly  optical depth to ULAS J1319+0950 is consistent with that measured towards similarly distant SDSS quasars, implying that results from optical- and NIR-selected quasars may be combined in studies of cosmological reionization. Also presented is a new NIR-spectrum of the previously discovered UKIDSS quasar ULAS J020332.38+001229.2, which reveals the object to be a broad absorption line quasar. The new spectrum shows that the emission line initially identified as Ly  is actually N V, leading to a revised redshift of z = 5.72, rather than z = 5.86 as previously estimatedPeer reviewe
A small area faint KX redshift survey for QSOs in the ESO Imaging Survey Chandra Deep Field South
In this paper we present preliminary spectroscopic results from a small area
faint K-excess (KX) survey, and compare KX selection against UVX selection. The
aim of the KX method is to produce complete samples of QSOs flux-limited in the
K band, in order to minimize any selection bias in samples of QSOs from the
effects of reddening and extinction. Using the photometric catalogue of the ESO
Imaging Survey Chandra Deep Field South (48 arcmin^2) we have identified
compact objects with J-K colours redder than the stellar sequence, that are
brighter than K=19.5. We have obtained spectra of 33 candidates, using the
LDSS++ spectrograph on the AAT. Amongst the 11 bluer candidates, with V-J<3,
three are confirmed as QSOs. Identification of the 22 redder candidates with
V-J>3 is substantially incomplete, but so far no reddened QSOs have been found.
Near-infrared spectroscopy will be more effective in identifying some of these
targets. Only two UVX (U-B<-0.2) sources brighter than K=19.5 are found which
are not also KX selected. These are both identified as galactic stars. Thus KX
selection appears to select all UVX QSOs. The surface density of QSOs in the
blue subsample (V-J<3) at K<19.5 is 325^+316_-177 deg^-2. Because
identification of the red subsample (V-J>3) is substantially incomplete, the
2sigma upper limit on the density of reddened QSO is large, <1150 deg^-2. As
anticipated, at these faint magnitudes the KX sample includes several compact
galaxies. Of the 14 with measured redshifts, there are roughly equal numbers of
early and late type objects. Nearly all the early type galaxies are found in a
single structure at z=0.66.Comment: 9 pages, 8 figures. Accepted for publication in MNRA
Evaluating the effectiveness of message design in accelerated online programs using a think aloud protocol
This study reviews the potential implications associated with message design, timing, and delivery on students in an Accelerated Online Program. Attention to participant verbal and physical reactions will be analyzed utilizing a non-positivistic Think Aloud Protocol on a select sample. The aspects of the study will enable researchers to obtain data related to individual reflections
Computational and experimental studies of the wide bandgap semiconductors NH<sub>4</sub>TiOF<sub>3</sub> and (NH<sub>4</sub>)<sub>2</sub>TiOF<sub>4</sub>
Photoactivated linkage isomerism in single crystals of nickel, palladium and platinum di-nitro complexes: A photocrystallographic investigation
The runaway binary LP 400−22 is leaving the Galaxy
We present optical spectroscopy, astrometry, radio and X-ray observations of the runaway binary LP 400−22. We refine the orbital parameters of the system based on our new radial velocity observations. Our parallax data indicate that LP 400−22 is significantly more distant (3σ lower limit of 840 pc) than initially predicted. LP 400−22 has a tangential velocity in excess of 830 km s^−1; it is unbound to the Galaxy. Our radio and X-ray observations fail to detect a recycled millisecond pulsar companion, indicating that LP 400−22 is a double white dwarf system. This essentially rules out a supernova runaway ejection mechanism. Based on its orbit, a Galactic Centre origin is also unlikely. However, its orbit intersects the locations of several globular clusters; dynamical interactions between LP 400−22 and other binary stars or a central black hole in a dense cluster could explain the origin of this unusual binary
Solid-state interconversions:Unique 100 % reversible transformations between the ground and metastable states in single-crystals of a series of nickel(II) nitro complexes
The No-Triangle Hypothesis for N=8 Supergravity
We study the perturbative expansion of N=8 supergravity in four dimensions
from the viewpoint of the ``no-triangle'' hypothesis, which states that
one-loop graviton amplitudes in N=8 supergravity only contain scalar box
integral functions. Our computations constitute a direct proof at six-points
and support the no-triangle conjecture for seven-point amplitudes and beyond.Comment: 43page
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