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

Practising Cultural Inclusivity During the Pandemic: A Case Study of an Online Composition Course in Canada

The PhoeNX Ensemble-Memorial University composition course offers a case study of university-level pedagogical, intercultural music-making and its potential to engage the question of how music education can help to address existing racial and cultural tensions in society. During the course, racial and cultural concerns surfaced when participants negotiated their individual positionalities. An analysis of the multifaceted interactions demonstrates how this composition course exemplifies a meaningful and valuable path toward inclusive and anti-racist pedagogy in the Canadian classroom. Such approaches can address cultural misunderstanding and social injustice in the university context.Le cours de composition « Ensemble PhoeNX » de l’Université Memorial permet une étude de cas de production musicale pédagogique et interculturelle au niveau universitaire, qui a le potentiel d’aborder la question de la façon dont l’enseignement musical peut contribuer à traiter des tensions raciales et culturelles existant dans la société. Durant ce cours, des préoccupations raciales et culturelles sont apparues lorsque les participant.e.s ont négocié leur position individuelle. Une analyse de ces interactions complexes montre en quoi ce cours de composition constitue un exemple d’un cheminement significatif et appréciable vers une pédagogie inclusive et antiraciste dans une salle de classe au Canada. De telles approches peuvent répondre à l’incompréhension culturelle et à l’injustice sociale en contexte universitaire

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