3,116 research outputs found
Fractal templates in the escape dynamics of trapped ultracold atoms
We consider the dynamic escape of a small packet of ultracold atoms launched
from within an optical dipole trap. Based on a theoretical analysis of the
underlying nonlinear dynamics, we predict that fractal behavior can be seen in
the escape data. This data would be collected by measuring the time-dependent
escape rate for packets launched over a range of angles. This fractal pattern
is particularly well resolved below the Bose-Einstein transition temperature--a
direct result of the extreme phase space localization of the condensate. We
predict that several self-similar layers of this novel fractal should be
measurable and we explain how this fractal pattern can be predicted and
analyzed with recently developed techniques in symbolic dynamics.Comment: 11 pages with 5 figure
Violations of local realism by two entangled quNits
Results obtained in two recent papers, \cite{Kaszlikowski} and \cite{Durt},
seem to indicate that the nonlocal character of the correlations between the
outcomes of measurements performed on entangled systems separated in space is
not robust in the presence of noise. This is surprising, since entanglement
itself is robust. Here we revisit this problem and argue that the class of
gedanken-experiments considered in \cite{Kaszlikowski} and \cite{Durt} is too
restrictive. By considering a more general class, involving sequences of
measurements, we prove that the nonlocal correlations are in fact robust.Comment: Reference added, 3 pages, accepted for publication in J. Phys. A:
Math. and Genera
Hadron plus photon production in polarized hadronic collisions at next-to-leading order accuracy
We compute the next-to-leading order QCD corrections to the polarized (and
unpolarized) cross sections for the production of a hadron accompanied by an
opposite-side prompt photon. This process, being studied at RHIC, permits us to
reconstruct partonic kinematics using experimentally measurable variables. We
study the correlation between the reconstructed momentum fractions and the true
partonic ones, which in the polarized case might allow us to reveal the
spin-dependent gluon distribution with a higher precision.Comment: 18 figures included. New version, discussion about polarized
asymmetries extended, 7 new figures, new reference
Direct determinations of the nucleon and pion terms at nearly physical quark masses
We present a high statistics study of the pion and nucleon light and strange
quark sigma terms using dynamical non-perturbatively improved clover
fermions with a range of pion masses down to MeV and several
volumes, up to , and lattice spacings, fm,
enabling a study of finite volume and discretisation effects for MeV. Systematics are found to be reasonably under control. For the nucleon
we obtain MeV and MeV, or equivalently
in terms of the quark fractions, , and
, where the errors include estimates of both the systematic
and statistical uncertainties. These values, together with perturbative
matching in the heavy quark limit, lead to ,
and . In addition, through the use of the
(inverse) Feynman-Hellmann theorem our results for are shown
to be consistent with the nucleon masses determined in the analysis. For the
pion we implement a method which greatly reduces excited state contamination to
the scalar matrix elements from states travelling across the temporal boundary.
This enables us to demonstrate the Gell-Mann-Oakes-Renner expectation
over our range of pion masses.Comment: 31 pages, 18 figures, v2, small changes to text and figure
Recommended from our members
Synthesis and Study of Olefin Metathesis Catalysts Supported by Redox-Switchable Diaminocarbene 3 Ferrocenophanes
A redox-switchable ligand, N,N'-dimethyldiaminocarbene[3]ferrocenophane (5), was synthesized and incorporated into a series of Ir- and Ru-based complexes. Electrochemical and spectroscopic analyses of (5) Ir(CO)(2)Cl (15) revealed that 5 displayed a Tolman electronic parameter value of 2050 cm(-1) in the neutral state and 2061 cm(-1) upon oxidation. Moreover, inspection of X-ray crystallography data recorded for (5) Ir(cis,cis-1,5-cyclooctadiene)Cl (13) revealed that 5 was sterically less bulky (%V-Bur = 28.4) than other known diaminocarbene[3]ferrocenophanes, which facilitated the synthesis of (5)(PPh3)Cl2Ru-(3-phenylindenylid-1-ene) (18). Complex 18 exhibited quasi-reversible electrochemical processes at 0.79 and 0.98 V relative to SCE, which were assigned to the Fe and Ru centers in the complex, respectively, based on UV-vis and electron pair resonance spectroscopic measurements. Adding 2,3-dichloro-5,6-dicyanoquinone over the course of a ring-opening metathesis polymerization of cis, cis-1,5-cyclooctadiene catalyzed by 18 ([monomer](0)/[18](0) = 2500) reduced the corresponding rate constant of the reaction by over an order of magnitude (pre-oxidation: k(obs) = 0.045 s(-1); post-oxidation: k(obs) = 0.0012 s(-1)). Subsequent reduction of the oxidized species using decamethylferrocene restored catalytic activity (post-reduction: k(obs) = up to 0.016 s(-1), depending on when the reductant was added). The difference in the polymerization rates was attributed to the relative donating ability of the redox-active ligand (i.e., strongly donating 5 versus weakly donating 5(+)) which ultimately governed the activity displayed by the corresponding catalyst.U. S. Army Research Office W911NF-09-1-0446Chemistr
The Galaxy Angular Correlation Functions and Power Spectrum from the Two Micron All Sky Survey
We calculate the angular correlation function of galaxies in the Two Micron
All Sky Survey. We minimize the possible contamination by stars, dust, seeing
and sky brightness by studying their cross correlation with galaxy density, and
limiting the galaxy sample accordingly. We measure the correlation function at
scales between 1-18 arcdegs using a half million galaxies. We find a best fit
power law to the correlation function has a slope of 0.76 and an amplitude of
0.11. However, there are statistically significant oscillations around this
power law. The largest oscillation occurs at about 0.8 degrees, corresponding
to 2.8 h^{-1} Mpc at the median redshift of our survey, as expected in halo
occupation distribution descriptions of galaxy clustering.
We invert the angular correlation function using Singular Value Decomposition
to measure the three-dimensional power spectrum and find that it too is in good
agreement with previous measurements. A dip seen in the power spectrum at small
wavenumber k is statistically consistent with CDM-type power spectra. A fit of
CDM-type power spectra to k < 0.2 h Mpc^{-1} give constraints of
\Gamma_{eff}=0.116 and \sigma_8=0.96. This suggest a K_s-band linear bias of
1.1+/-0.2. This \Gamma_{eff} is different from the WMAP CMB derived value. On
small scales the power-law shape of our power spectrum is shallower than that
derived for the SDSS. These facts together imply a biasing of these different
galaxies that might be nonlinear, that might be either waveband or luminosity
dependent, and that might have a nonlocal origin.Comment: 14 pages, 20 figures, to be published in ApJ January 20th, revision
included two new figures, version with high resolution figures can be found
here http::ww
Looking for symmetric Bell inequalities
Finding all Bell inequalities for a given number of parties, measurement
settings, and measurement outcomes is in general a computationally hard task.
We show that all Bell inequalities which are symmetric under the exchange of
parties can be found by examining a symmetrized polytope which is simpler than
the full Bell polytope. As an illustration of our method, we generate 238885
new Bell inequalities and 1085 new Svetlichny inequalities. We find, in
particular, facet inequalities for Bell experiments involving two parties and
two measurement settings that are not of the
Collins-Gisin-Linden-Massar-Popescu type.Comment: Joined the associated website as an ancillary file, 17 pages, 1
figure, 1 tabl
Bolla Bollana boulder beds:A Neoproterozoic trough mouth fan in South Australia?
The Bolla Bollana Formation is an exceptionally thick (ca 1500 m), rift-related sedimentary succession cropping out in the northern Flinders Ranges, South Australia, which was deposited during the Sturtian (mid Cryogenian) glaciation. Lithofacies analysis reveals three distinct facies associations which chart changing depositional styles on an ice-sourced subaqueous fan system. The diamictite facies association is dominant, and comprises both massive and stratified varieties with a range of clast compositions and textures, arranged into thick beds (1 to 20 m), representing stacked, ice-proximal glaciogenic debris-flow deposits. A channel belt facies association, most commonly consisting of normally graded conglomerates and sandstones, displays scour and fill structure of ca 10 m width and 1 to 3 m depth: these strata are interpreted as channelized turbidites. Rare mud-filled channels in this facies association bear glacially striated lonestones. Finally, a sheet heterolithics facies association contains a range of conglomerates through sandstones to silty shales arranged into clear, normally graded cycles from the lamina to bed scale. These record a variety of non-channelized turbidites, probably occupying distal and/or inter-channel locations on the subaqueous fan. Coarsening and thickening-up cycles, capped by dolomicrites or mudstones, are indicative of lobe build out and abandonment, potentially as a result of ice lobe advance and stagnation. Dropstones, recognized by downwarped and punctured laminae beneath pebbles to boulders in shale, or in delicate climbing ripple cross-laminated siltstones, are clearly indicative of ice rafting. The co-occurrence of ice-rafted debris and striated lonestones strongly supports a glaciogenic sediment source for the diamictites. Comparison to Pleistocene analogues enables an interpretation as a trough mouth fan, most probably deposited leeward of a palaeo-ice stream. Beyond emphasizing the highly dynamic nature of Sturtian ice sheets, these interpretations testify to the oldest trough mouth fan recorded to date.Daniel P. Le Heron, Marie E. Busfield, and Alan S. Collin
Synchrotron x-ray scattering of magnetic and electronic structure of UN and U2N3 epitaxial films
We examine the magnetic ordering of UN and of a closely related nitride,
U2N3, by preparing thin epitaxial films and using synchrotron x-ray techniques.
The magnetic configuration and subsequent coupling to the lattice are key
features of the electronic structure. The well-known antiferromagnetic (AF)
ordering of UN is confirmed, but the expected accompanying distortion at Tn is
not observed. Instead, we propose that the strong magneto-elastic interaction
at low temperature involves changes in the strain of the material. These
strains vary as a function of the sample form. As a consequence, the accepted
AF configuration of UN may be incorrect. In the case of cubic a-U2N3, no single
crystals have been previously prepared, and we have determined the AF ordering
wave-vector. The AF Tn is close to that previously reported. In addition,
resonant diffraction methods have identified an aspherical quadrupolar charge
contribution in U2N3 involving the 5f electrons; the first time this has been
observed in an actinide compound
An X-ray Selected Galaxy Cluster at z=1.26
We report the discovery of an X-ray luminous galaxy cluster at z=1.26.
RXJ0848.9+4452 was selected as an X-ray cluster candidate in the ROSAT Deep
Cluster Survey, on the basis of its spatial extent. Deep optical and near-IR
imaging have revealed a galaxy overdensity around the peak of the X-ray
emission, with a significant excess of red objects with J-K colors typical of
elliptical galaxies at z>1. Spectroscopic observations at the Keck II telescope
have secured 6 galaxy redshifts in the range 1.257=1.261), within
a 35 arcsec radius around the peak X-ray emission. This system lies only 4.2
arcmin away (5.0 h^{-1}_{50} comoving Mpc, q_0=0.5) from the galaxy cluster ClG
J0848+4453, which was identified by Stanford et al. (1997) at z=1.273 in a
near-IR field galaxy survey, and is also known to be X-ray luminous. Assuming
that the X-ray emission is entirely due to hot intra-cluster gas, both these
systems have similar rest frame luminosities L_x ~=1x10^{44} ergs/s (0.5-2.0
keV band). In combination with our spectrophotometric data for the entire 30
arcmin^2 field, this suggests the presence of a superstructure, consisting of
two collapsed, possibly virialized clusters, the first detected to date at z>1.Comment: To appear in The Astronomical Journal, 24 pages, 8 figures, 1 color
jpg plate (fig.7), see http://www.eso.org/~prosati/lynx/plate_fig7.jp
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