Global and Local Two-Sample Tests via Regression

Two-sample testing is a fundamental problem in statistics. Despite its long history, there has been renewed interest in this problem with the advent of high-dimensional and complex data. Specifically, in the machine learning literature, there have been recent methodological developments such as classification accuracy tests. The goal of this work is to present a regression approach to comparing multivariate distributions of complex data. Depending on the chosen regression model, our framework can efficiently handle different types of variables and various structures in the data, with competitive power under many practical scenarios. Whereas previous work has been largely limited to global tests which conceal much of the local information, our approach naturally leads to a local two-sample testing framework in which we identify local differences between multivariate distributions with statistical confidence. We demonstrate the efficacy of our approach both theoretically and empirically, under some well-known parametric and nonparametric regression methods. Our proposed methods are applied to simulated data as well as a challenging astronomy data set to assess their practical usefulness

The Nature of Solar Polar Rays

We use time series observations from the SOHO and Yohkoh spacecraft to study solar polar rays. Contrary to our expectations, we find that the rays are associated with active regions on the sun and are not features of the polar coronal holes. They are extended, hot plasma structures formed in the active regions and projected onto the plane of the sky above the polar coronal holes. We present new observations and simple projection models that match long-lived polar ray structures seen in limb synoptic maps. Individual projection patterns last for at least 5 solar rotations.Comment: 10 pages, 5 PostScript figures. Fig.1 is in color. The paper is also available at http://www.ifa.hawaii.edu/users/jing/papers.htm

Vortex structures of rotating spin-orbit coupled Bose-Einstein condensates

We consider the quasi-2D two-component Bose-Einstein condensates with Rashba spin-orbit (SO) coupling in a rotating trap. An external Zeeman term favoring spin polarization along the radial direction is also considered, which has the same form as the non-canonical part of the mechanical angular momentum. The rotating condensate exhibits rich structures as varying the strengths of trapping potential and interaction. With a strong trapping potential, the condensate exhibits a half-quantum vortex-lattice configuration. Such a configuration is driven to the normal one by introducing the external radial Zeeman field. In the case of a weak trap potential, the condensate exhibits a multi-domain pattern of plane-wave states under the external radial Zeeman field.Comment: 8 pages, 7 figures, two figures are adde

Eigenstates of Paraparticle Creation Operators

Eigenstates of the parabose and parafermi creation operators are constructed. In the Dirac contour representation, the parabose eigenstates correspond to the dual vectors of the parabose coherent states. In order $p=2$, conserved-charge parabose creation operator eigenstates are also constructed. The contour forms of the associated resolutions of unity are obtained.Comment: 14 pages, LaTex file, no macros, no figure

The Pairwise Peculiar Velocity Dispersion of Galaxies: Effects of the Infall

We study the reliability of the reconstruction method which uses a modelling of the redshift distortions of the two-point correlation function to estimate the pairwise peculiar velocity dispersion of galaxies. In particular, the dependence of this quantity on different models for the infall velocity is examined for the Las Campanas Redshift Survey. We make extensive use of numerical simulations and of mock catalogs derived from them to discuss the effect of a self-similar infall model, of zero infall, and of the real infall taken from the simulation. The implications for two recent discrepant determinations of the pairwise velocity dispersion for this survey are discussed.Comment: minor changes in the discussion; accepted for publication in ApJ; 8 pages with 2 figures include

Current-induced forces and hot-spots in biased nano-junctions

We investigate theoretically the interplay of current-induced forces (CIF), Joule heating, and heat transport inside a current-carrying nano-conductor. We find that the CIF, due to the electron-phonon coherence, can control the spatial heat dissipation in the conductor. This yields a significant asymmetric concentration of excess heating (hot-spot) even for a symmetric conductor. When coupled to the electrode phonons, CIF drive different phonon heat flux into the two electrodes. First-principles calculations on realistic biased nano-junctions illustrate the importance of the effect.Comment: Phys. Rev. Lett. accepted versio

Organizational Cross-Cultural Adaptation Through Social Networks: A Multiple-Case Study Of Chinese Firms Operating In The United States

I report on the findings of an inductive, interpretive multiple-case study of organizational cross-cultural adaptation and answer the question of how foreign companies can overcome the challenges of fitting into their host environment. Based on in-depth interview data from nine Chinese firms operating in the United States, I explore the content and drivers of firm-level cross-cultural adaptation. The emergent framework demonstrates a dynamic and comprehensive process at the firm level, involving a multilevel and multidimensional adaptation to fit through social networking. The identified patterns of adaptors reveal the link between cross-cultural adaptation and functional fitness of firms in a foreign environment. The study also identifies the boundary conditions of the cross-cultural adaptation of foreign firms. In addition, the study highlights the previously underserved aspect of functional fitness in a foreign environment and its essential role in influencing a firm’s overseas performance