10,327 research outputs found
A Typical Medium Dynamical Cluster Approximation for the Study of Anderson Localization in Three Dimensions
We develop a systematic typical medium dynamical cluster approximation that
provides a proper description of the Anderson localization transition in three
dimensions (3D). Our method successfully captures the localization phenomenon
both in the low and large disorder regimes, and allows us to study the
localization in different momenta cells, which renders the discovery that the
Anderson localization transition occurs in a cell-selective fashion. As a
function of cluster size, our method systematically recovers the re-entrance
behavior of the mobility edge and obtains the correct critical disorder
strength for Anderson localization in 3D.Comment: 5 Pages, 4 Figures and Supplementary Material include
A NuSTAR Observation of the Gamma-ray Emitting Millisecond Pulsar PSR J1723-2837
We report on the first NuSTAR observation of the gamma-ray emitting
millisecond pulsar binary PSR J1723-2837. X-ray radiation up to 79 keV is
clearly detected and the simultaneous NuSTAR and Swift spectrum is well
described by an absorbed power-law with a photon index of ~1.3. We also find
X-ray modulations in the 3-10 keV, 10-20 keV, 20-79 keV, and 3-79 keV bands at
the 14.8-hr binary orbital period. All these are entirely consistent with
previous X-ray observations below 10 keV. This new hard X-ray observation of
PSR J1723-2837 provides strong evidence that the X-rays are from the
intrabinary shock via an interaction between the pulsar wind and the outflow
from the companion star. We discuss how the NuSTAR observation constrains the
physical parameters of the intrabinary shock model.Comment: Accepted for publication in ApJ. 5 pages, 3 figure
Evolution of pairing from weak to strong coupling on a honeycomb lattice
We study the evolution of the pairing from weak to strong coupling on a
honeycomb lattice by Quantum Monte Carlo. We show numerical evidence of the
BCS-BEC crossover as the coupling strength increases on a honeycomb lattice
with small fermi surface by measuring a wide range of observables: double
occupancy, spin susceptibility, local pair correlation, and kinetic energy.
Although at low energy, the model sustains Dirac fermions, we do not find
significant qualitative difference in the BCS-BEC crossover as compared to
those with an extended Fermi surface, except at weak coupling, BCS regime.Comment: 5 page
Truncated α1-antitrypsin as an infection biomarker for Severe Acute Respiratory Syndrome (SARS)
published_or_final_versio
Cluster Persistence: a Discriminating Probe of Soap Froth Dynamics
The persistent decay of bubble clusters in coarsening two-dimensional soap
froths is measured experimentally as a function of cluster volume fraction.
Dramatically stronger decay is observed in comparison to soap froth models and
to measurements and calculations of persistence in other systems. The fraction
of individual bubbles that contain any persistent area also decays, implying
significant bubble motion and suggesting that T1 processes play an important
role in froth persistence.Comment: 5 pages, revtex, 4 eps figures. To appear in Europhys. Let
Swift, XMM-Newton, and NuSTAR observations of PSR J2032+4127/MT91 213
We report our recent Swift, NuSTAR, and XMM-Newton X-ray and Lijiang optical
observations on PSR J2032+4127/MT91 213, the gamma-ray binary candidate with a
period of 45-50 years. The coming periastron of the system was predicted to be
in November 2017, around which high-energy flares from keV to TeV are expected.
Recent studies with Chandra and Swift X-ray observations taken in 2015/16
showed that its X-ray emission has been brighter by a factors of ~10 than that
before 2013, probably revealing some on-going activities between the pulsar
wind and the stellar wind. Our new Swift/XRT lightcurve shows no strong
evidence of a single vigorous brightening trend, but rather several strong
X-ray flares on weekly to monthly timescales with a slowly brightening
baseline, namely the low state. The NuSTAR and XMM-Newton observations taken
during the flaring and the low states, respectively, show a denser environment
and a softer power-law index during the flaring state, implying that the pulsar
wind interacted with stronger stellar winds of the companion to produce the
flares. These precursors would be crucial in studying the predicted giant
outburst from this extreme gamma-ray binary during the periastron passage in
late 2017.Comment: 6 pages, including 3 figures and 2 tables. Accepted for publication
in Ap
Low-Reynolds number swimming in gels
Many microorganisms swim through gels, materials with nonzero zero-frequency
elastic shear modulus, such as mucus. Biological gels are typically
heterogeneous, containing both a structural scaffold (network) and a fluid
solvent. We analyze the swimming of an infinite sheet undergoing transverse
traveling wave deformations in the "two-fluid" model of a gel, which treats the
network and solvent as two coupled elastic and viscous continuum phases. We
show that geometric nonlinearities must be incorporated to obtain physically
meaningful results. We identify a transition between regimes where the network
deforms to follow solvent flows and where the network is stationary. Swimming
speeds can be enhanced relative to Newtonian fluids when the network is
stationary. Compressibility effects can also enhance swimming velocities.
Finally, microscopic details of sheet-network interactions influence the
boundary conditions between the sheet and network. The nature of these boundary
conditions significantly impacts swimming speeds.Comment: 6 pages, 5 figures, submitted to EP
Some estimates of Wang-Yau quasilocal energy
Given a spacelike 2-surface in a spacetime and a constant future
timelike unit vector in , we derive upper and lower estimates
of Wang-Yau quasilocal energy for a given isometric
embedding of into a flat 3-slice in . The quantity itself depends on the choice of , however the infimum of
over does not. In particular, when lies
in a time symmetric 3-slice in and has nonnegative Brown-York quasilocal
mass \mby(\Sigma), our estimates show that equals \mby (\Sigma). We also study the spatial limit of , where is a large coordinate sphere in a
fixed end of an asymptotically flat initial data set and is
an isometric embeddings of into .
We show that if has future timelike ADM energy-momentum, then
equals the ADM mass
of .Comment: 17 page
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