14,641 research outputs found
Penalized Orthogonal-Components Regression for Large p Small n Data
We propose a penalized orthogonal-components regression (POCRE) for large p
small n data. Orthogonal components are sequentially constructed to maximize,
upon standardization, their correlation to the response residuals. A new
penalization framework, implemented via empirical Bayes thresholding, is
presented to effectively identify sparse predictors of each component. POCRE is
computationally efficient owing to its sequential construction of leading
sparse principal components. In addition, such construction offers other
properties such as grouping highly correlated predictors and allowing for
collinear or nearly collinear predictors. With multivariate responses, POCRE
can construct common components and thus build up latent-variable models for
large p small n data.Comment: 12 page
Heavy Quark Effective Theory on the Light Front
The light-front heavy quark effective theory is derived to all orders in
. In the limit , the theory exhibits the familiar
heavy quark spin-flavor symmetry. This new formalism permits a straightforward
canonical quantization to all orders in ; moreover, higher order terms
have rather simple operator structures. The light-front heavy quark effective
theory can serve as an useful framework for the study of non-perturbative QCD
dynamics of heavy hadron bound states.Comment: 11 pages, revtex, no figure
Single-electron turnstile pumping with high frequencies
In this Letter, we present a theoretical analysis to single-electron pumping
operation in a large range of driving frequencies through the time-dependent
tunneling barriers controlled by external gate voltages. We show that the
single-electron turnstile works at the frequency lower than the characteristic
frequency which is determined by the mean average electron tunneling rate. When
the driving frequency is greater than the characteristic frequency of electron
tunnelings, fractional electron pumping occurs as an effect of quantum
coherence tunneling.Comment: 4 pages, 5 figure
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