Connected Spatial Networks over Random Points and a Route-Length Statistic

We review mathematically tractable models for connected networks on random points in the plane, emphasizing the class of proximity graphs which deserves to be better known to applied probabilists and statisticians. We introduce and motivate a particular statistic $R$ measuring shortness of routes in a network. We illustrate, via Monte Carlo in part, the trade-off between normalized network length and $R$ in a one-parameter family of proximity graphs. How close this family comes to the optimal trade-off over all possible networks remains an intriguing open question. The paper is a write-up of a talk developed by the first author during 2007--2009.Comment: Published in at http://dx.doi.org/10.1214/10-STS335 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Modeling the reconstructed BAO in Fourier space

The density field reconstruction technique, which was developed to partially reverse the nonlinear degradation of the Baryon Acoustic Oscillation (BAO) feature in the galaxy redshift surveys, has been successful in substantially improving the cosmology constraints from recent galaxy surveys such as Baryon Oscillation Spectroscopic Survey (BOSS). We estimate the efficiency of the reconstruction method as a function of various reconstruction details. To directly quantify the BAO information in nonlinear density fields before and after reconstruction, we calculate the cross-correlations (i.e., propagators) of the pre(post)-reconstructed density field with the initial linear field using a mock galaxy sample that is designed to mimic the clustering of the BOSS CMASS galaxies. The results directly provide the BAO damping as a function of wavenumber that can be implemented into the Fisher matrix analysis. We focus on investigating the dependence of the propagator on a choice of smoothing filters and on two major different conventions of the redshift-space density field reconstruction that have been used in literature. By estimating the BAO signal-to-noise for each case, we predict constraints on the angular diameter distance and Hubble parameter using the Fisher matrix analysis. We thus determine an optimal Gaussian smoothing filter scale for the signal-to-noise level of the BOSS CMASS. We also present appropriate BAO fitting models for different reconstruction methods based on the first and second order Lagrangian perturbation theory in Fourier space. Using the mock data, we show that the modified BAO fitting model can substantially improve the accuracy of the BAO position in the best fits as well as the goodness of the fits.Comment: 21 pages, 7 figures, 1 table. Minor revisions. Matches version accepted by MNRA

Transverse electric current induced by optically injected spin current in cross-shaped InGaAs/InAlAs system

We examine electric response of a linearly polarized light normally shed on a cross-shaped quasi 2-dimensional InGaAs/InAlAs system with structure inversion asymmetry. The photo-excited conduction electrons carry a pure spin current with in-plane spin polarization due to the Rashba spin-orbit interaction. We use Landauer-B\"{u}ttiker formalism to show that this spin current induces two inward or outward transverse charge currents, which are observable in experiments. This effect may serve as an experimental probe of certain types of spin current.Comment: 5 pages, 3 figure

Topological Anderson Insulator

Disorder plays an important role in two dimensions, and is responsible for striking phenomena such as metal insulator transition and the integral and fractional quantum Hall effects. In this paper, we investigate the role of disorder in the context of the recently discovered topological insulator, which possesses a pair of helical edge states with opposing spins moving in opposite directions and exhibits the phenomenon of quantum spin Hall effect. We predict an unexpected and nontrivial quantum phase termed "topological Anderson insulator," which is obtained by introducing impurities in a two-dimensional metal; here disorder not only causes metal insulator transition, as anticipated, but is fundamentally responsible for creating extended edge states. We determine the phase diagram of the topological Anderson insulator and outline its experimental consequences.Comment: 4 pages, 4 figure

The Life and Works of Professor Yorifusa Ishida (1932-2015): A Pioneer of Planning History in Japan

Professor Yorifusa Ishida (1932-2015), who was an IPHS council member, was one of the leading scholars in the research field of city planning in the post-war Japan. His research interest expands so widely to include planning system, planning history, land readjustment, building line, land use controls and planning, development profit, rural planning and citizen participation. He has publicized his research findings, practical proposals, and academic and political views in many books, articles and academic papers. It is rather unfortunate, however, that most of them are published in Japanese and so his attainments are not well known by scholars outside Japan with few exceptions.In this paper, we first trace his life as researcher and professor mainly at Tokyo Metropolitan University. Then we try to review as many academic writings of his as possible in a systematic way in order to analyze the development of his research interests and attainments in his academic carrier for over 40 years. This was made possible because we have obtained fairly detailed information of his curriculum vitae and his publications list thanks to his surviving family.In this analysis, we focus upon his attainments in planning history in particular. Our questions will include:(1) What is, in his framework and interest, the relationship between the research of planning history and that of city planning as a whole?(2) What are his specific and distinctive contributions in the field of planning history? (3) What is his view of planning history, which we need to analyze critically and may be able to learn form?(4) What is the impacts of the western (German, French, British and American) planning upon his research?In conclusion, we try to evaluate the roll of Professor Ishida in the entire history of city planning research in Japan