2,973 research outputs found
Phase diagram of a dilute fermion gas with density imbalance
We map out the phase diagram of a dilute two-component atomic fermion gas
with unequal populations and masses under a Feshbach resonance. As in the case
of equal masses, no uniform phase is stable for an intermediate coupling
regime. For majority component heavier, the unstable region moves towards the
BEC side. When the coupling strength is increased from the normal phase, there
is an increased parameter space where the transition is into the FFLO state.
The converse is true if the majority is light.Comment: Proceeding for MS-HTSC VIII meeting, July 9-14 2006, Dresden; To
appear in Physica
InPCM: a network caching technique for improving the performance of TCP in wireless ad-hoc networks
We propose a novel mechanism called In-Network Packet Caching Mechanism (inPCM) to address TCP\u27s poor performance in IEEE 802.11 based multi-hop wireless networks. In particular, we address TCP\u27s inappropriate response to bursty and location dependent errors. The key concept is the use of intermediate nodes to perform packet recovery on behalf of TCP senders, similar to the well-known Snoop TCP but adapted to work over multi-hop wireless networks. We have conducted ns-2 simulation studies over a variety of network conditions and topologies. Our results confirm InPCM\u27s benefits to TCP in terms of delay and throughput. Moreover, it is immediately deployable without modifications to current protocols
Wave climatology in the Apostle Islands, Lake Superior
The wave climate of the Apostle Islands in Lake Superior for 35 year (1979–2013) was hindcast and examined using a third‐generation spectral wave model. Wave measurements within the Apostle Islands and offshore NOAA buoys were used to validate the model. Statistics of the significant wave height, peak wave period, and mean wave direction were computed to reveal the spatial variability of wave properties within the archipelago for average and extreme events. Extreme value analysis was performed to estimate the significant wave height at the 1, 10, and 100 year return periods. Significant wave heights in the interior areas of the islands vary spatially but are approximately half those immediately offshore of the islands. Due to reduced winter ice cover and a clockwise shift in wind direction over the hindcast period, long‐term trend analysis indicates an increasing trend of significant wave heights statistics by as much as 2% per year, which is approximately an order of magnitude greater than similar analysis performed in the global ocean for areas unaffected by ice. Two scientific questions related to wave climate are addressed. First, the wave climate change due to the relative role of changing wind fields or ice covers over the past 35 years was revealed. Second, potential bluff erosion affected by the change of wave climate and the trend of lower water levels in the Apostle Islands, Lake Superior was examined.Key Points:Wave climate of the Apostle Islands in Lake Superior for 35 year was hindcastStatistics of the wave climate reveal the spatial variability of wave propertiesAn increasing trend of SWH is found due to climate changePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113131/1/jgrc21305.pd
Exact partition functions of the Ising model on MxN planar lattices with periodic-aperiodic boundary conditions
The Grassmann path integral approach is used to calculate exact partition
functions of the Ising model on MxN square (sq), plane triangular (pt) and
honeycomb (hc) lattices with periodic-periodic (pp), periodic-antiperiodic
(pa), antiperiodic-periodic (ap) and antiperiodic-antiperiodic (aa) boundary
conditions. The partition functions are used to calculate and plot the specific
heat, , as a function of the temperature, . We find that
for the NxN sq lattice, for pa and ap boundary conditions are different
from those for aa boundary conditions, but for the NxN pt and hc lattices,
for ap, pa, and aa boundary conditions have the same values. Our exact
partition functions might also be useful for understanding the effects of
lattice structures and boundary conditions on critical finite-size corrections
of the Ising model.Comment: 17 pages, 13 Postscript figures, uses iopams.sty, submitted to J.
Phys. A: Math. Ge
Exploring quantum phase transitions by the cross derivative of the ground state energy
In this work, the cross derivative of the Gibbs free energy, initially
proposed for phase transitions in classical spin models [Phys. Rev. B 101,
165123 (2020)], is extended for quantum systems. We take the spin-1 XXZ chain
with anisotropies as an example to demonstrate its effectiveness and
convenience for the Gaussian-type quantum phase transitions therein. These
higher-order transitions are very challenging to determine by conventional
methods. From the cross derivative with respect to the two anisotropic
strengths, a single valley structure is observed clearly in each system size.
The finite-size extrapolation of the valley depth shows a perfect logarithmic
divergence, signaling the onset of a phase transition. Meanwhile, the critical
point and the critical exponent for the correlation length are obtained by a
power-law fitting of the valley location in each size. The results are well
consistent with the best estimations in the literature. Its application to
other quantum systems with continuous phase transitions is also discussed
briefly.Comment: 7 pages, 7 figure
Unveiling Significant Shoreline Changes in Lake Michigan After a Record-Setting Water Level Increase using High-Resolution Satellite Images
In this paper, high-resolution multispectral satellite images were used to
uncover a remarkable shoreline transformation in Lake Michigan coastal areas,
driven by a record-setting increase in the water level between 2013 and 2020.
Shoreline change analyses were conducted for eleven different natural beaches
around the lake, unveiling significant variations of shoreline retreat despite
being affected by the same water level increase. The average observed shoreline
retreats between 2013 and 2020 for the beaches ranged between 20 m and 62 m.
When the passive inundation was excluded, the estimated morphological changes
were found to differ significantly from site to site, with some locations
experiencing minimal changes, while others encountered considerable
morphological changes of up to 38m. The examination of the correlation between
the morphological changes and ten hydrodynamic and morphological factors
revealed strong correlations with the offshore slopes and beach width, with
steeply sloping, wide beaches experiencing more erosion. Notably, wave power,
longshore sediment transport divergence, and the number of storms exhibited
moderate correlation with the observed morphological changes. The results of
the shoreline changes and correlation analysis offer valuable insights into the
varied effects of increased water levels on Lake Michigan beaches, including
erosion and passive inundation, while shedding light on the key factors driving
shoreline erosion in this context. These insights can help decision and
policymakers in making informed choices regarding the protection and management
of Lake Michigan coastal areas, particularly in anticipation of future
incidents of water level increase
Interlayer pair tunneling and gap anisotropy in YBaCuO
Recent ARPES measurement observed a large -axis gap anisotropy,
, in clean YBaCuO. This
indicates that some sub-dominant component may exist in the -wave
dominant gap. We propose that the interlayer pairing tunneling contribution can
be determined through the investigation of the order parameter anisotropy.
Their potentially observable features in transport and spin dynamics are also
studied.Comment: 4 pages, 3 figure
Orbital occupation and magnetic moments of tetrahedrally coordinated iron in CaBaFe4O7
CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+
ions in tetrahedral coordination. Here we characterize its magnetic properties
by magnetization measurements and investigate its local electronic structure
using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination
with multiplet cluster and spin-resolved band structure calculations. We found
that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active
with the high-spin e^2 (up) t2^3 (up) e^1 (down) configuration having a
x^2-y^2-like electron for the minority spin. We deduce that there is an
appreciable orbital moment of about L_z=0.36 caused by multiplet interactions,
thereby explaining the observed magnetic anisotropy. CaBaFe4O7, a member of the
'114' oxide family, offers new opportunities to explore charge, orbital and
spin physics in transition metal oxides
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