Hypergraph pp-Laplacian: A Differential Geometry View

The graph Laplacian plays key roles in information processing of relational data, and has analogies with the Laplacian in differential geometry. In this paper, we generalize the analogy between graph Laplacian and differential geometry to the hypergraph setting, and propose a novel hypergraph $p$-Laplacian. Unlike the existing two-node graph Laplacians, this generalization makes it possible to analyze hypergraphs, where the edges are allowed to connect any number of nodes. Moreover, we propose a semi-supervised learning method based on the proposed hypergraph $p$-Laplacian, and formalize them as the analogue to the Dirichlet problem, which often appears in physics. We further explore theoretical connections to normalized hypergraph cut on a hypergraph, and propose normalized cut corresponding to hypergraph $p$-Laplacian. The proposed $p$-Laplacian is shown to outperform standard hypergraph Laplacians in the experiment on a hypergraph semi-supervised learning and normalized cut setting.Comment: Extended version of our AAAI-18 pape

The Evolution of High Temperature Plasma in Magnetar Magnetospheres and its Implications for Giant Flares

In this paper we propose a new mechanism describing the initial spike of giant flares in the framework of the starquake model. We investigate the evolution of a plasma on a closed magnetic flux tube in the magnetosphere of a magnetar in the case of a sudden energy release and discuss the relationship with observations of giant flares. We perform one-dimensional numerical simulations of the relativistic magnetohydrodynamics in Schwarzschild geometry. We assume energy is injected at the footpoints of the loop by a hot star surface containing random perturbations of the transverse velocity. Alfv\'en waves are generated and propagate upward, accompanying very hot plasma that is also continuously heated by nonlinearly generated compressive waves. We find that the front edges of the fireball regions collide at the top of the tube with their symmetrically launched counterparts. This collision results in an energy release which can describe the light curve of initial spikes of giant flares.Comment: 13 pages, 11 figures, accepted for publication in Ap

An Agent that Facilitates Crowd Discussion

Online discussion platforms are perceived as the next-generation method of citizen involvement. Such platforms can collect, integrate, and synthesize opinions to achieve social good. Crowd-scale platforms are being developed and deployed in social experiments that involve citizens and local governments. In such platforms, human facilitation is often used to preserve the quality of the discussions. Human facilitators often face difficulties when the discussions grow in size. In this paper, we present “D-agree, ” a crowd-scale discussion support system based on an automated facilitation agent. The agent extracts discussion structures from online discussions, analyzes them, and posts facilitation messages. We conducted small- and large-scale social experiments in Japan to assess the social impact of the platform. The results showcase the success of our automated facilitation agents in gathering valuable opinions from citizens. In addition, our experiments highlight the effect of an automated facilitation agent on online discussions. In particular, we find that combining the agent facilitator with human facilitators leads to higher user satisfaction

Information-seeking behaviour of community pharmacists during the COVID-19 pandemic: an ecological study

[Objective] To evaluate the information-seeking behaviour of pharmacists during the COVID-19 pandemic and its relation to COVID-19 and related infections and deaths within the local prefecture. [Design] Ecological study. [Setting] Japan—47 prefectures. [Methods] The number of accesses to a Japanese web page established by the Pharmacy Informatics Group to disseminate information about infection control and the number of infections and deaths in 47 prefectures were investigated from 6 April to 30 September 2020 using the access information on the web page and publicly available information. [Results] During the first 6 months of the COVID-19 pandemic, the total number of accesses was 226 130 (range: 10 984–138 898 per month), the total number of infections was 78 761 (1738–31 857) and the total number of deaths was 1470 (39–436). The correlation between the total number of accesses and that of infections per 100 000 individuals in 47 prefectures was r=0.72 (95% CI 0.55 to 0.83, p<0.001), and between the total number of accesses and deaths per 100 000 individuals in 47 prefectures was r=0.44 (95% CI 0.17 to 0.65, p=0.002). [Conclusions] The information-seeking behaviour of community pharmacists correlated positively with infection status within the community