2,735 research outputs found
Arithmetic of higher-dimensional orbifolds and a mixed Waring problem
We study the density of rational points on a higher-dimensional orbifold (Pnâ1,Î) when Î is a Q-divisor involving hyperplanes. This allows us to address a question of Tanimoto about whether the set of rational points on such an orbifold constitutes a thin set. Our approach relies on the HardyâLittlewood circle method to first study an asymptotic version of Waringâs problem for mixed powers. In doing so we make crucial use of the recent resolution of the main conjecture in Vinogradovâs mean value theorem, due to BourgainâDemeterâGuth and Wooley
An investigation of children's peer trust across culture: is the composition of peer trust universal?
The components of children's trust in same-gender peers (trust beliefs, ascribed trustworthiness, and dyadic reciprocal trust) were examined in samples of 8- to 11-year-olds from the UK, Italy, and Japan. Trust was assessed by children's ratings of the extent to which same-gender classmates kept promises and kept secrets. Social relations analyses confirmed that children from each country showed significant: (a) actor variance demonstrating reliable individual differences in trust beliefs, (b) partner variance demonstrating reliable individual differences in ascribed trustworthiness, and (c ) relationship variance demonstrating unique relationships between interaction partners. Cultural differences in trust beliefs and ascribed trustworthiness also emerged and these differences were attributed to the tendency for children from cultures that value societal goals to share personal information with the peer group
The Phase Diagram of the Sigma Model
We study the phase diagram of the scalar model in
dimensions. We find that the phase transition is of first order in most of the
parameter space. The theory can still be relevant to continuum physics (as an
effective theory) provided the transition is sufficiently weakly first order.
This places restrictions on the allowed coupling constants.Comment: 3 pages (Latex), 2 eps figures, uses espcrc2.sty, epsf, talk given at
LATTICE9
Quantum Hall Effect, Screening and Layer-Polarized Insulating States in Twisted Bilayer Graphene
We investigate electronic transport in dual-gated twisted bilayer graphene.
Despite the sub-nanometer proximity between the layers, we identify independent
contributions to the magnetoresistance from the graphene Landau level spectrum
of each layer. We demonstrate that the filling factor of each layer can be
independently controlled via the dual gates, which we use to induce Landau
level crossings between the layers. By analyzing the gate dependence of the
Landau level crossings, we characterize the finite inter-layer screening and
extract the capacitance between the atomically-spaced layers. At zero filling
factor, we observe magnetic and displacement field dependent insulating states,
which indicate the presence of counter-propagating edge states with inter-layer
coupling.Comment: 4 pages, 3 figure
Tunneling in graphene-topological insulator hybrid devices
Hybrid graphene-topological insulator (TI) devices were fabricated using a
mechanical transfer method and studied via electronic transport. Devices
consisting of bilayer graphene (BLG) under the TI BiSe exhibit
differential conductance characteristics which appear to be dominated by
tunneling, roughly reproducing the BiSe density of states. Similar
results were obtained for BLG on top of BiSe, with 10-fold greater
conductance consistent with a larger contact area due to better surface
conformity. The devices further show evidence of inelastic phonon-assisted
tunneling processes involving both BiSe and graphene phonons. These
processes favor phonons which compensate for momentum mismatch between the TI
and graphene points. Finally, the utility of these tunnel
junctions is demonstrated on a density-tunable BLG device, where the
charge-neutrality point is traced along the energy-density trajectory. This
trajectory is used as a measure of the ground-state density of states
Large-scale distributions of mid- and far-infrared emission from the center to the halo of M82 revealed with AKARI
The edge-on starburst galaxy M82 exhibits complicated distributions of
gaseous materials in its halo, which include ionized superwinds driven by
nuclear starbursts, neutral materials entrained by the superwinds, and
large-scale neutral streamers probably caused by a past tidal interaction with
M81. We investigate detailed distributions of dust grains and polycyclic
aromatic hydrocarbons (PAHs) around M82 to understand their interplay with the
gaseous components. We performed mid- (MIR) and far-infrared (FIR) observations
of M82 with the Infrared Camera and Far-Infrared Surveyor on board AKARI. We
obtain new MIR and FIR images of M82, which reveal both faint extended emission
in the halo and very bright emission in the center with signal dynamic ranges
as large as five and three orders of magnitude for the MIR and FIR,
respectively. We detect MIR and FIR emission in the regions far away from the
disk of the galaxy, reflecting the presence of dust and PAHs in the halo of
M82. We find that the dust and PAHs are contained in both ionized and neutral
gas components, implying that they have been expelled into the halo of M82 by
both starbursts and galaxy interaction. In particular, we obtain a tight
correlation between the PAH and H emission, which provides evidence
that the PAHs are well mixed in the ionized superwind gas and outflowing from
the disk.Comment: 12 pages, 8 figures, accepted for publication in A&
Potassium-40 evalution of performance tested bulls
"Demand for quality beef with a minimum amount of fat is ever increasing. Progressive beef producers have been working toward a leaner beef animal for several years. Industry and research likewise have joined in this goal and have produced instruments which enable the producer to evaluate animals more objectively and accurately. The Whole Body Counter is one of those instruments. It measures the radioactive potassium (40K) present in the live animal. The amount of 40K present is then used to estimate the percent lean and percent fat in the live animal. Potassium (40K) is primarily located in the fat-free portion of the body, especially the muscle."--First page.John W. Massey, Toshihiro Yamagishi, and D.W. Vogt (Department of Animal Science, College of Agriculture)Revised 10/84/8
Synthesis of infinite-layer LaNiO2 films by metal-organic deposition
We report the synthesis of infinite-layer LaNiO2 thin films by metal organic
decomposition. Our work is aimed to synthesize perovskite-like oxides with 3d9
electronic configuration, which is common to high-Tc copper oxides. The 3d9
configuration is very rare in oxides other than cuprates. Ni1+ oxides, even
though Ni1+ is an unusual oxidation state, may be one of very few candidates.
One example of the Ni1+ phases is infinite-layer LaNiO2. The bulk synthesis of
LaNiO2 is difficult, but we demonstrate in this article that the thin-film
synthesis of LaNiO2 by metal organic decomposition is rather easy. This is due
to the advantage of thin films with a large-surface-to-volume ratio, which
makes oxygen diffusion prompt. Resistivity measurements indicate that LaNiO2 is
essentially a metal but unfortunately with no trace of superconductivity yet.Comment: 13 pages, 4 figure
Dilepton and Photon Emission Rates from a Hadronic Gas III
We extend our early analyses of the dilepton and photon emission rates from a
hadronic gas to account for strange mesons using a density expansion. The
emission rates are reduced to vacuum correlation functions using three-flavor
chiral reduction formulas, and the latters are assessed in terms of empirical
data. Using a fire-ball, we compare our results to the low and intermediate
mass dilepton data available from CERN. Our results suggest that a baryon free
hadronic gas does not account for the excess of low mass dielectrons observed
at CERES but do well in accounting for the intermediate dimuons at HELIOS. The
same observations apply to the recent low and high dielectron rates from
CERES.Comment: 12 pages LaTeX, 11 eps figure
Large-scale mapping of the massive star-forming region RCW38 in the [CII] and PAH emission
We investigate the large-scale structure of the interstellar medium (ISM)
around the massive star cluster RCW38 in the [CII] 158 um line and polycyclic
aromatic hydrocarbon (PAH) emission. We carried out [CII] line mapping of an
area of ~30'x15' for RCW~38 by a Fabry-Perot spectrometer on a 100 cm
balloon-borne telescope with an angular resolution of ~1'.5. We compared the
[CII] intensity map with the PAH and dust emission maps obtained by the AKARI
satellite. The [CII] emission shows a highly nonuniform distribution around the
cluster, exhibiting the structure widely extended to the north and the east
from the center. The [CII] intensity rapidly drops toward the southwest
direction, where a CO cloud appears to dominate. We decompose the 3-160 um
spectral energy distributions of the surrounding ISM structure into PAH as well
as warm and cool dust components with the help of 2.5-5 um spectra. We find
that the [CII] emission spatially corresponds to the PAH emission better than
to the dust emission, confirming the relative importance of PAHs for
photo-electric heating of gas in photo-dissociation regions. A naive
interpretation based on our observational results indicates that molecular
clouds associated with RCW38 are located both on the side of and behind the
cluster.Comment: 10 pages, 7 figures, accepted for publication in A&
- âŠ