Penalized single-index quantile regression

This article is made available through the Brunel Open Access Publishing Fund. Copyright for this article is retained by the author(s), with first publication rights granted to the journal. This is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).The single-index (SI) regression and single-index quantile (SIQ) estimation methods product linear combinations of all the original predictors. However, it is possible that there are many unimportant predictors within the original predictors. Thus, the precision of parameter estimation as well as the accuracy of prediction will be effected by the existence of those unimportant predictors when the previous methods are used. In this article, an extension of the SIQ method of Wu et al. (2010) has been proposed, which considers Lasso and Adaptive Lasso for estimation and variable selection. Computational algorithms have been developed in order to calculate the penalized SIQ estimates. A simulation study and a real data application have been used to assess the performance of the methods under consideration

On the effective lagrangian in spinor electrodynamics with added violation of Lorentz and CPT symmetries

We consider quantum electrodynamics with additional coupling of spinor fields to the space-time independent axial vector violating both Lorentz and CPT symmetries. The Fock-Schwinger proper time method is used to calculate the one-loop effective action up to the second order in the axial vector and to all orders in the space-time independent electromagnetic field strength. We find that the Chern-Simons term is not radiatively induced and that the effective action is CPT invariant in the given approximation.Comment: 17 pages, LaTeX, v.2, minor changes, Eqs.(5.12) and (5.13) added, misprints correcte

Single-index quantile regression

This is the post-print version of the final paper published in Journal of Multivariate Analysis. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.Nonparametric quantile regression with multivariate covariates is a difficult estimation problem due to the “curse of dimensionality”. To reduce the dimensionality while still retaining the flexibility of a nonparametric model, we propose modeling the conditional quantile by a single-index function View the MathML sourceg0(xTγ0), where a univariate link function g0(⋅)g0(⋅) is applied to a linear combination of covariates View the MathML sourcexTγ0, often called the single-index. We introduce a practical algorithm where the unknown link function g0(⋅)g0(⋅) is estimated by local linear quantile regression and the parametric index is estimated through linear quantile regression. Large sample properties of estimators are studied, which facilitate further inference. Both the modeling and estimation approaches are demonstrated by simulation studies and real data applications

What are the left-handed media and what is interesting about them?

We review the intensively discussed ideas about wave propagation and refraction in media where both electric permittivity and magnetic permeability are negative. The criticism against negative refraction as violating the causality principle is considered. Starting from the initial wave equations, refraction of beams at the boundary of a left-handed medium is analyzed. The physics of a perfect lens formed by a flat layer of a left-handed material is considered.Comment: 21 pages, 8 figure

TPP and Trans-Pacific Perplexities

In the past few years, the United States has been busy negotiating the Trans-Pacific Partnership (TPP) Agreement with countries in the Asia-Pacific region. These countries include Australia, Brunei Darussalam, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam. Although it remains unclear which chapters or provisions will be included in the final text of the TPP Agreement, the negotiations have been quite controversial. In addition to the usual concerns about having high standards that are heavily lobbied by industries and arguably inappropriate for many participating countries, the TPP negotiations have been heavily criticized for their secrecy and lack of transparency, accountability and democratic participation. Written for the inaugural annual Asia-Pacific issue of the Fordham International Law Journal, this article does not seek to continue this line of criticism, although transparency, accountability and democratic participation remain highly important. Nor does the article aim to explore the agreement\u27s implications for each specific trade sector. Instead, this Article focuses on the ramifications of the exclusion of four different parties or groups of parties from the TPP negotiations: (1) China; (2) BRICS and other emerging economies; (3) Europe; and (4) civil society organizations. Targeting these TPP outsiders and using illustrations from the intellectual property sector and the larger trade context, this article seeks to highlight the perplexities created by the TPP negotiations. It cautions policymakers, commentators and the public at large against the negotiations\u27 considerable and largely overlooked costs

The Harmonization Game: What Basketball Can Teach About Intellectual Property and International Trade

In the recent World Men\u27s Basketball Championships in Indianapolis, Team USA found out painfully that the international game is very different from what they play at home and that the gap between USA Basketball and the rest of the world has been closing. While the United States\u27 losses might have a significant impact on how the country will prepare for the 2004 Olympics in Athens and on how Americans train youngsters to play basketball, their teachings go beyond basketball. The international harmonization process is a game with different rules, different officials, and players with different visions and mindsets. By watching how players interact with rules, officials, and other players, one therefore could gain insight into globalization and the international harmonization process. Team USA\u27s recent loss might be a painful lesson to Americans, but it provides a beneficial lesson to all of us who are involved in intellectual property and international trade