11,567 research outputs found
Assembly Bias and Splashback in Galaxy Clusters
We use publicly available data for the Millennium Simulation to explore the
implications of the recent detection of assembly bias and splashback signatures
in a large sample of galaxy clusters. These were identified in the SDSS/DR8
photometric data by the redMaPPer algorithm and split into high- and
low-concentration subsamples based on the projected positions of cluster
members. We use simplified versions of these procedures to build cluster
samples of similar size from the simulation data. These match the observed
samples quite well and show similar assembly bias and splashback signals.
Previous theoretical work has found the logarithmic slope of halo density
profiles to have a well-defined minimum whose depth decreases and whose radius
increases with halo concentration. Projected profiles for the observed and
simulated cluster samples show trends with concentration which are opposite to
these predictions. In addition, for high-concentration clusters the minimum
slope occurs at significantly smaller radius than predicted. We show that these
discrepancies all reflect confusion between splashback features and features
imposed on the profiles by the cluster identification and concentration
estimation procedures. The strong apparent assembly bias is not reflected in
the three-dimensional distribution of matter around clusters. Rather it is a
consequence of the preferential contamination of low-concentration clusters by
foreground or background groups.Comment: 17 pages, 16 figures, 3 tables, accepted versio
Pairing of a harmonically trapped fermionic Tonks-Girardeau gas
The fermionic Tonks-Girardeau (FTG) gas is a one-dimensional spin-polarized
Fermi gas with infinitely strong attractive zero-range odd-wave interactions,
arising from a confinement-induced resonance reachable via a three-dimensional
p-wave Feshbach resonance. We investigate the off-diagonal long-range order
(ODLRO) of the FTG gas subjected to a longitudinal harmonic confinement by
analyzing the two-particle reduced density matrix for which we derive a
closed-form expression. Using a variational approach and numerical
diagonalization we find that the largest eigenvalue of the two-body density
matrix is of order N/2, where N is the total particle number, and hence a
partial ODLRO is present for a FTG gas in the trap.Comment: 4 pages, 3 figures, revtex
Vortex Dynamics in Anisotropic Traps
We investigate the dynamics of linear vortex lattices in anisotropic traps in
two-dimensions and show that the interplay between the rotation and the
anisotropy leads to a rich but highly regular dynamics.Comment: 6 pages, 6 figure
Boson Pairs in a One-dimensional Split Trap
We describe the properties of a pair of ultracold bosonic atoms in a
one-dimensional harmonic trapping potential with a tunable zero-ranged barrier
at the trap centre. The full characterisation of the ground state is done by
calculating the reduced single-particle density, the momentum distribution and
the two-particle entanglement. We derive several analytical expressions in the
limit of infinite repulsion (Tonks-Girardeau limit) and extend the treatment to
finite interparticle interactions by numerical solution. As pair interactions
in double wells form a fundamental building block for many-body systems in
periodic potentials, our results have implications for a wide range of
problems.Comment: 9 pages, 8 figure
Assessing the critical material constraints on low carbon infrastructure transitions
We present an assessment method to analyze whether the disruption in supply of a group of materials endangers the transition to low-carbon infrastructure. We define criticality as the combination of the potential for supply disruption and the exposure of the system of interest to that disruption. Low-carbon energy depends on multiple technologies comprised of a multitude of materials of varying criticality. Our methodology allows us to assess the simultaneous potential for supply disruption of a range of materials. Generating a specific target level of low-carbon energy implies a dynamic roll-out of technology at a specific scale. Our approach is correspondingly dynamic, and monitors the change in criticality during the transition towards a low-carbon energy goal. It is thus not limited to the quantification of criticality of a particular material at a particular point in time. We apply our method to criticality in the proposed UK energy transition as a demonstration, with a focus on neodymium use in electric vehicles. Although we anticipate that the supply disruption of neodymium will decrease, our results show the criticality of low carbon energy generation increases, as a result of increasing exposure to neodymium-reliant technologies. We present a number of potential responses to reduce the criticality through a reduction in supply disruption potential of the exposure of the UK to that disruption
Property investigation and sputter deposition of dispersion-hardened copper for fatigue specimen fabrication
Sputter-deposited alloys of dispersion-hardenable Cu-0.25 vol% SiC and Cu-0.50 vol% SiC and precipitation-hardenable Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr were investigated for selection to evaluate fatigue specimen performance with potential application in fabricating regeneratively cooled rocket thrust chambers. Yield strengths in the 700 to 1000-MN/sq m range were observed with uniform elongation ranging from 0.5 to 1.5% and necking indicative of greater ductility. Electrical conductivity measured as an analog to thermal conductivity gave values 90% IACS for Cu-0.15 wt% Zr and Cu-0.05 wt% Mg-0.15 wt% Zr-0.40 wt% Cr. A 5500-g sputtered deposit of Cu-0.15 wt% Zr alloy, 12.29 mm (0.484 in.) average thickness in the fatigue specimen gage length, was provided to NASA on one of their substrates
The 50-horsepower solar-powered irrigation facility located near Gila Bend, Arizona
The 50 horsepower solar powered irrigation facility near Gila Bend, Arizona which includes a Rankine cycle demonstrates the technical feasibility of solar powered pumping. The design of a facility specifically for the irrigation farmer using the technology that has been developed over the last four years is proposed
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