53,903 research outputs found
Fully Bayesian Penalized Regression with a Generalized Bridge Prior
We consider penalized regression models under a unified framework. The
particular method is determined by the form of the penalty term, which is
typically chosen by cross validation. We introduce a fully Bayesian approach
that incorporates both sparse and dense settings and show how to use a type of
model averaging approach to eliminate the nuisance penalty parameters and
perform inference through the marginal posterior distribution of the regression
coefficients. We establish tail robustness of the resulting estimator as well
as conditional and marginal posterior consistency for the Bayesian model. We
develop a component-wise Markov chain Monte Carlo algorithm for sampling.
Numerical results show that the method tends to select the optimal penalty and
performs well in both variable selection and prediction and is comparable to,
and often better than alternative methods. Both simulated and real data
examples are provided
Hot Spots on the Fermi Surface of Bi2212: Stripes versus Superstructure
In a recent paper Saini et al. have reported evidence for a pseudogap around
(pi,0) at room temperature in the optimally doped superconductor Bi2212. This
result is in contradiction with previous ARPES measurements. Furthermore they
observed at certain points on the Fermi surface hot spots of high spectral
intensity which they relate to the existence of stripes in the CuO planes. They
also claim to have identified a new electronic band along Gamma-M1 whose one
dimensional character provides further evidence for stripes. We demonstrate in
this Comment that all the measured features can be simply understood by
correctly considering the superstructure (umklapp) and shadow bands which occur
in Bi2212.Comment: 1 page, revtex, 1 encapsulated postscript figure (color
Existence and non-existence of area-minimizing hypersurfaces in manifolds of non-negative Ricci curvature
We study minimal hypersurfaces in manifolds of non-negative Ricci curvature,
Euclidean volume growth and quadratic curvature decay at infinity. By
comparison with capped spherical cones, we identify a precise borderline for
the Ricci curvature decay. Above this value, no complete area-minimizing
hypersurfaces exist. Below this value, in contrast, we construct examples.Comment: 31 pages. Comments are welcome
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