4,302 research outputs found
Infinitely Robust Order and Local Order-Parameter Tulips in Apollonian Networks with Quenched Disorder
For a variety of quenched random spin systems on an Apollonian network,
including ferromagnetic and antiferromagnetic bond percolation and the Ising
spin glass, we find the persistence of ordered phases up to infinite
temperature over the entire range of disorder. We develop a
renormalization-group technique that yields highly detailed information,
including the exact distributions of local magnetizations and local spin-glass
order parameters, which turn out to exhibit, as function of temperature,
complex and distinctive tulip patterns.Comment: 5 pages, 4 figures; updated to reflect minor changes in published
versio
Frustrated Further-Neighbor Antiferromagnetic and Electron-Hopping Interactions in the d=3 tJ Model: Finite-Temperature Global Phase Diagrams from Renormalization-Group Theory
The renormalization-group theory of the d=3 tJ model is extended to
further-neighbor antiferromagnetic or electron-hopping interactions, including
the ranges of frustration. The global phase diagram of each model is calculated
for the entire ranges of temperatures, electron densities, and
further/first-neighbor interaction strength ratios. In addition to the
\tau_{tJ} phase seen in earlier studies of the nearest-neighbor d=3 tJ model,
the \tau_{Hb} phase seen before in the d=3 Hubbard model appears both near and
away from half-filling. These distinct \tau phases potentially correspond to
different (BEC-like and BCS-like) superconducting phases.Comment: Improved figures, added discussions, added references. Published
version. 12 pages, 5 figures, 6 table
Infinitely Robust Order and Local Order-Parameter Tulips in Apollonian Networks with Quenched Disorder
For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder. We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local
magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns
On Toroidal Horizons in Binary Black Hole Inspirals
We examine the structure of the event horizon for numerical simulations of
two black holes that begin in a quasicircular orbit, inspiral, and finally
merge. We find that the spatial cross section of the merged event horizon has
spherical topology (to the limit of our resolution), despite the expectation
that generic binary black hole mergers in the absence of symmetries should
result in an event horizon that briefly has a toroidal cross section. Using
insight gained from our numerical simulations, we investigate how the choice of
time slicing affects both the spatial cross section of the event horizon and
the locus of points at which generators of the event horizon cross. To ensure
the robustness of our conclusions, our results are checked at multiple
numerical resolutions. 3D visualization data for these resolutions are
available for public access online. We find that the structure of the horizon
generators in our simulations is consistent with expectations, and the lack of
toroidal horizons in our simulations is due to our choice of time slicing.Comment: Submitted to Phys. Rev.
Conflict Or Congruence? Maternal and Infant-Centric Factors Associated With Shorter Exclusive Breastfeeding Durations Among the Tsimane
Six months of exclusive breastfeeding (EBF) is considered optimal for infant health, though globally most infants begin complementary feeding (CF) earlier—including among populations that practice prolonged breastfeeding. Two frameworks for understanding patterns of early CF emerge in the literature. In the first, maternal and infant needs trade-off, as “maternal-centric” factors—related to time and energy demands, reproductive investment, cultural influences, and structural barriers— favor supplanting breastfeeding with earlier and increased CF. A second framework considers that “infant-centric” factors—related to infant energetic needs—favor CF before six months to supplement breastfeeding. We apply these two frameworks in examining early CF among the Tsimane—a high-fertility, high-mortality, forager-horticulturalist population residing in the Bolivian Amazon. Data were collected from a mixed-longitudinal sample of 161 Tsimane mother-infant pairs from August 2012 – April 2013. Tsimane mothers generally reported introducing CF because of perceived infant needs. However, CF is introduced with continued intensive breastfeeding, and generally coupled with premastication. Risks of earlier CF relative to the minimum hazard (estimated at 5 births) were elevated for lower and higher parity mothers, but were significantly greater only after 9 births. Seventeen percent of mothers reported introducing CF because of low milk supply. Introducing CF because of low milk was most common from 0-3 months of age and among higher parity mothers, which may reflect physiological constraints. Maternal reproductive trade-offs and perceived infant needs may help explain the low prevalence of EBF to six months among other populations in which breastfeeding is not structurally or culturally constrained
A Decade of Experience Using mTor Inhibitors in Liver Transplantation
Some studies suggest that Sirolimus (SRL) is associated with an increased risk of death in liver transplant recipients compared to treatment with calcineurin inhibitors (CNIs). We compared patients who received SRL or CNI in the first year after liver transplant. Our database included 688 patients who received a liver transplant. The patients were divided into groups. (1) CNI + MPS (mycophenolate sodium) at time of discharge. (2) CNI + MPS at time of discharge; SRL was added within the first 6 months and continued through the first year. (3) CNI + MPS at time of discharge; SRL was added within the first 6 months and discontinued before the first year. (4) SRL as primary immunosuppression. (5) SRL as primary immunosuppression and discontinued before the first year. We used mortality and graft loss as the primary measures of outcome. We also quantified renal function using the change in glomerular filtration rate (GFR), the presence of biopsy proven acute cellular reject (ACR), and steroid-resistant rejection (SRR). There were no significant differences in mortality or graft loss. There was no difference in patient or graft survival. Patients that received SRL as primary immunosuppression had 50% less rejection compared to controls
Brane World Susy Breaking from String/M Theory
String and M-theory realizations of brane world supersymmetry breaking
scenarios are considered in which visible sector Standard Model fields are
confined on a brane, with hidden sector supersymmetry breaking isolated on a
distant brane. In calculable examples with an internal manifold of any volume
the Kahler potential generically contains brane--brane non-derivative contact
interactions coupling the visible and hidden sectors and is not of the no-scale
sequestered form. This leads to non-universal scalar masses and without
additional assumptions about flavor symmetries may in general induce dangerous
sflavor violation even though the Standard Model and supersymmetry branes are
physically separated. Deviations from the sequestered form are dictated by bulk
supersymmetry and can in most cases be understood as arising from exchange of
bulk supergravity fields between branes or warping of the internal geometry.
Unacceptable visible sector tree-level tachyons arise in many models but may be
avoided in certain classes of compactifications. Anomaly mediated and gaugino
mediated contributions to scalar masses are sub-dominant except in special
circumstances such as a flat or AdS pure five--dimensional bulk geometry
without bulk vector multiplets.Comment: Latex, 83 pages, references adde
Unravelling quantum carpets: a travelling wave approach
Quantum carpets are generic spacetime patterns formed in the probability
distributions P(x,t) of one-dimensional quantum particles, first discovered in
1995. For the case of an infinite square well potential, these patterns are
shown to have a detailed quantitative explanation in terms of a travelling-wave
decomposition of P(x,t). Each wave directly yields the time-averaged structure
of P(x,t) along the (quantised)spacetime direction in which the wave
propagates. The decomposition leads to new predictions of locations, widths
depths and shapes of carpet structures, and results are also applicable to
light diffracted by a periodic grating and to the quantum rotator. A simple
connection between the waves and the Wigner function of the initial state of
the particle is demonstrated, and some results for more general potentials are
given.Comment: Latex, 26 pages + 6 figures, submitted to J. Phys. A (connections
with prior literature clarified
The Statistics of Supersonic Isothermal Turbulence
We present results of large-scale three-dimensional simulations of supersonic
Euler turbulence with the piecewise parabolic method and multiple grid
resolutions up to 2048^3 points. Our numerical experiments describe
non-magnetized driven turbulent flows with an isothermal equation of state and
an rms Mach number of 6. We discuss numerical resolution issues and demonstrate
convergence, in a statistical sense, of the inertial range dynamics in
simulations on grids larger than 512^3 points. The simulations allowed us to
measure the absolute velocity scaling exponents for the first time. The
inertial range velocity scaling in this strongly compressible regime deviates
substantially from the incompressible Kolmogorov laws. The slope of the
velocity power spectrum, for instance, is -1.95 compared to -5/3 in the
incompressible case. The exponent of the third-order velocity structure
function is 1.28, while in incompressible turbulence it is known to be unity.
We propose a natural extension of Kolmogorov's phenomenology that takes into
account compressibility by mixing the velocity and density statistics and
preserves the Kolmogorov scaling of the power spectrum and structure functions
of the density-weighted velocity v=\rho^{1/3}u. The low-order statistics of v
appear to be invariant with respect to changes in the Mach number. For
instance, at Mach 6 the slope of the power spectrum of v is -1.69, and the
exponent of the third-order structure function of v is unity. We also directly
measure the mass dimension of the "fractal" density distribution in the
inertial subrange, D_m = 2.4, which is similar to the observed fractal
dimension of molecular clouds and agrees well with the cascade phenomenology.Comment: 15 pages, 19 figures, ApJ v665, n2, 200
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