Emergence of a Chern-insulating state from a semi-Dirac dispersion

A Chern insulator (quantum anomalous Hall insulator) phase is demonstrated to exist in a typical semi-Dirac system, the TiO2/VO2 heterostructure. By combining first-principles calculations with Wannier-based tight-binding model, we calculate the Berry curvature distribution, finding a Chern number of -2 for the valence bands, and demonstrate the existence of gapless chiral edge states, ensuring quantization of the Hall conductivity to 2e^2/h. A new semi-Dirac model, where each semi-Dirac cone is formed by merging three conventional Dirac points, is proposed to reveal how the nontrivial topology with finite Chern number is compatible with a semi-Dirac electronic spectrum.Comment: 12 pages, 3 figure

Ethical Dilemma and Nihilism in Munro\u27s Passion

In their article Ethical Dilemma and Nihilism in Munro\u27s \u27Passion\u27 Xiying Liu and Hongbin Dai discuss ethical issues in Alice Munro\u27s short story Passion. When attempting to escape the shackles of multiple ethical identities, the short story\u27s protagonist Grace encounters dilemmas and in consequence makes wrong decisions with regard to the principle of ethics. The other protagonist of the story, Neil, commits suicide demonstrating that he breaks off all relationship with the world. Liu and Dai argue that Neil\u27s death deconstructs Grace\u27s ethical dilemmas and thus the narrative constructs a sense of nihilism. Liu and Dai posit that Munro\u27s short story reveals the humility, fragility, and complexity of human nature

Bridging the gap between training and inference for spatio-temporal forecasting

Spatio-temporal sequence forecasting is one of the fundamental tasks in spatio-temporal data mining. It facilitates many real world applications such as precipitation now casting, city wide crowd flow prediction and air pollution forecasting. Recently, a few Seq2Seq based approaches have been proposed, but one of the drawbacks of Seq2Seq models is that, small errors can accumulate quickly along the generated sequence at the inference stage due to the different distributions of training and inference phase. That is because Seq2Seq models minimise single step errors only during training, however the entire sequence has to be generated during the inference phase which generates a discrepancy between training and inference. In this work, we propose a novel curriculum learning based strategy named Temporal Progressive Growing Sampling to effectively bridge the gap between training and inference for spatio-temporal sequence forecasting, by transformin the training process from a fully-supervised manner which utilises all available previous groundtruth values to a less-supervised manner which replaces some of theground-truth context with generated predictions. To do that we sam-ple the target sequence from midway outputs from intermediate models trained with bigger timescales through a carefully designed decaying strategy. Experimental results demonstrate that our proposed method better models long term dependencies and outperforms baseline approaches on two competitive datasets

Does Education Pay in Urban China? Estimating Returns to Education Using Twins

This paper empirically estimates the returns to education using twins data that the authors collected from urban China. Our ordinary least-squares estimate shows that one year of schooling increases an individual¡¦s earnings by 8.4 percent. However, once we use the within-twin-pair fixed effects model, the return is reduced to 2.7 percent, which suggests that much of the estimated returns to education in China that have been found in previous studies are due to omitted ability or the family effect. This finding suggests that well-educated people are faring well in China mainly because of their superior ability or family background advantages, rather than because of knowledge that they acquired at school. We further investigate why the true return is low and the omitted ability bias high, and find evidence that it may be a consequence of the distinct education system in China, which is highly selective and exam oriented. More specifically, we find that high school education mainly serves as a mechanism to select college students, and has zero returns in terms of earnings. In contrast, both vocational school education and college education have a large return that is comparable to that found in rich Western countries.

Why Does Spousal Education Matter for Earnings? Assortative Mating or Cross-productivity

In interpreting the positive relationship between spousal education and one's earnings, economists have two major hypotheses: cross-productivity between couples and assortative mating. However, no prior empirical study has been able to separate the two effects. This paper empirically disentangles the two effects by using twins data that we collected from urban China. We have two major innovations: we use twins data to control for the unobserved mating effect in our estimations, and we estimate both current and wedding-time earnings equations. Arguably, the cross-productivity effect takes time to be realized and thus is relatively unimportant at the time of the wedding. Any effect of spousal education on wedding-time earnings should more likely be the mating effect. We find that both cross-productivity and mating are important in explaining the current earnings. Although the mating effect exists for both husbands and wives, the cross-productivity effect only runs from Chinese husbands to wives. We further show that the cross-productivity effect is realized by increasing the hourly wage rate rather than working hours.

Economic Returns to Communist Party Membership: Evidence from Chinese Twins

This paper empirically estimates the returns to membership of the Chinese Communist Party using unique twins data that the authors collected from urban China. Our ordinary least squares estimate shows that being a Party member increases earnings by 28.1 percent, but when we use a within-twin-pair fixed-effects model, the effect of Party membership all but disappears, which suggests that much of the estimated value of Party membership that is given in the literature is due to the effects of omitted ability or family background. The findings suggest that Party members fare well not because of their special political status per se, but because of the superior ability that allowed them to pass through the strict Party membership selection process.