We present a lattice-QCD calculation of the B → π ν semileptonic form factors and a new determination of the CKM matrix element |V ub |. We use the MILC asqtad 2+1-flavor lattice configurations at four lattice spacings and light-quark masses down to 1/20 of the physical strange-quark mass. We extrapolate the lattice form factors to the continuum using staggered chiral perturbation theory in the hard-pion and SU(2) limits. We employ a model-independent z parameterization to extrapolate our lattice form factors from large-recoil momentum to the full kinematic range. We introduce a new functional method to propagate information from the chiral-continuum extrapolation to the z expansion. We present our results together with a complete systematic error budget, including a covariance matrix to enable the combination of our form factors with other lattice-QCD and experimental results. To obtain |V ub |, we simultaneously fit the experimental data for the B → π ν differential decay rate obtained by the BaBar and Belle collaborations together with our lattice form-factor results. We find |V ub | = (3.72 ± 0.16) × 10 −3 where the error is from the combined fit to lattice plus experiments and includes all sources of uncertainty. Our form-factor results bring the QCD error on |V ub | to the same level as the experimental error. We also provide results for the B → π ν vector and scalar form factors obtained from the combined lattice and experiment fit, which are more precisely-determined than from our lattice-QCD calculation alone. These results can be used in other phenomenological applications and to test other approaches to QCD.
The slowly evolving gauge coupling of gauge-fermion systems near the conformal window makes numerical investigations of these models challenging. We consider finite size scaling and show that this often used technique leads to inconsistent results if the leading order scaling corrections are neglected. When the corrections are included the results become consistent not only between different operators but even when data obtained at different gauge couplings or with different lattice actions are combined. Our results indicate that the SU(3) 12-fermion system is conformal with mass anomalous dimension γm = 0.235(15).
Age, sex, ethnicity, urban-rural residence, economic condition, religious involvement, and daily exercise are significantly associated with levels of frailty. Hazard analyses further reveal that the FI is a robust predictor of mortality at advanced ages and that the relationship between frailty and mortality is independent of various covariates. Discussion The measurement and analysis of frailty have broad implications for public health initiatives designed to target individuals with the diminished capacity to effectively compensate for external stressors and to prevent further declines associated with aging and mortality. A key to healthy longevity is the prevention, postponement, and potential recovery from physical and cognitive deficits at advanced ages through enhanced medical interventions and treatments.
Using the example of the two-dimensional (2D) Ising model, we show that in contrast to what can be done in configuration space, the tensor renormalization group (TRG) formulation allows one to write exact, compact, and manifestly local blocking formulas and exact coarse grained expressions for the partition function. We argue that similar results should hold for most models studied by lattice gauge theorists. We provide exact blocking formulas for several 2D spin models (the O(2) and O(3) sigma models and the SU(2) principal chiral model) and for the 3D gauge theories with groups Z_2, U(1) and SU(2). We briefly discuss generalizations to other groups, higher dimensions and practical implementations.Comment: 12 pages, 10 figure
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