On a question of Babadi and Tarokh

In a recent remarkable paper, Babadi and Tarokh proved the "randomness" of sequences arising from binary linear block codes in the sense of spectral distribution, provided that their dual distances are sufficiently large. However, numerical experiments conducted by the authors revealed that Gold sequences which have dual distance 5 also satisfy such randomness property. Hence the interesting question was raised as to whether or not the stringent requirement of large dual distances can be relaxed in the theorem in order to explain the randomness of Gold sequences. This paper improves their result on several fronts and provides an affirmative answer to this question

Determine the galaxy bias factors on large scales using bispectrum method

We study whether the bias factors of galaxies can be unbiasedly recovered from their power spectra and bispectra. We use a set of numerical N-body simulations and construct large mock galaxy catalogs based upon the semi-analytical model of Croton et al. (2006). We measure the reduced bispectra for galaxies of different luminosity, and determine the linear and first nonlinear bias factors from their bispectra. We find that on large scales down to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly constant, and b1 obtained with the bispectrum method agrees very well with the expected value. The nonlinear bias factor b2 is negative, except for the most luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of galaxies is consistent with the b2 mass dependence of their host halos. We show that it is essential to have an accurate estimation of the dark matter bispectrum in order to have an unbiased measurement of b1 and b2. We also test the analytical approach of incorporating halo occupation distribution to model the galaxy power spectrum and bispectrum. The halo model predictions do not fit the simulation results well on the precision requirement of current cosmological studies.Comment: 9 pages, 8 figures, accepted for publication in Ap

Topological Kondo Insulators

This article reviews recent theoretical and experimental work on a new class of topological material - topological Kondo insulators, which develop through the interplay of strong correlations and spin-orbit interactions. The history of Kondo insulators is reviewed along with the theoretical models used to describe these heavy fermion compounds. The Fu-Kane method of topological classification of insulators is used to show that hybridization between the conduction electrons and localized f-electrons in these systems gives rise to interaction-induced topological insulating behavior. Finally, some recent experimental results are discussed, which appear to confirm the theoretical prediction of the topological insulating behavior in Samarium hexaboride, where the long-standing puzzle of the residual low-temperature conductivity has been shown to originate from robust surface states.Comment: Accepted as an article in the Annual Review of Condensed Matter Physics, Volume 7 (2016

A Comparative Study of Sino-US Festival Culture

Festival culture is an important carrier of the emotion and spirit of a nation. The study of holiday culture is an indispensable part of the study of a national culture. Since both American culture and Chinese culture have the characteristics of diversity and pluralism, a comparative study of them is meaningful. This paper studies some of the major festivals in both China and the United States of America, compares the similarities and the differences in the festival practices and trys to reveal the national personality, cultural value orientation, and the national spirit of them for the purpose of a better understanding and harmonious developmeng of the two cultures. Keywords: festival culture; comparative study; Sino-USRésumé: La culture festival est un vecteur important de l'émotion et l'esprit d'une nation. L'étude de la culture de vacances est un élément indispensable de l'étude d'une culture nationale. Comme la culture américaine et la culture chinoises ont toutes les deux les caractéristiques de la diversité et du pluralisme, une étude comparative d'entre eux est significative. Cet article étudie plusieurs grands festivaux en Chine et aux États-Unis, compare les similitudes et les différences dans les pratiques de festival et essaie de révéler la personnalité nationale, l'orientation des valeurs culturelles et l'esprit national pour une meilleure compréhension et un developpement harmonieux de ces deux cultures.Mots-clés: culture festival; étude comparative; sino-américai