Back Reaction of 4D Conformal Fields on Static Geometry

Static, spherically symmetric solutions to the semi-classical Einstein equation are studied, including the effect of the quantum energy-momentum tensor for conformal matters with 4D Weyl anomaly. Through both perturbative and non-perturbative methods, we show that the quantum effect can play a crucial role in shaping the near-horizon geometry, and that the existence of the horizon requires fine-tuning.Comment: 35 pages, minor modificatio

ヨツボシモンシデムシにおける養育行動の個体群間変異の探索と形質間相関の解明（英文）

Parental care is a prime example of altruism and has evolved across a wide range of taxa. Although parental care is common in mammals,birds, fishes and some invertebrate groups, there is considerable variation in reproductive effort (called parental investment) among species. Understanding the factors underlying the origin and maintenance of the variation contributes to uncovering the ultimate drivers of the emergence of complex family life and social behavior. Theoretical and empirical studies have shown that the optimal amount of parental investment for offspring exceeds that of its parent, and consequently the power balance between the parents and offspring determines the amount provided. Previous studies have reported individual traits in parents and offspring can influence investment, though in reality a set of coevolved traits in both parties will contribute to determine the optimal investment level. Hence, it is essential to investigate the correlation between multiple traits, and how this is related to the variation in parental investment. Herein, I use natural intraspecific variation in the amount of parental investment in a burying beetle Nicrophorus quadripunctatus to investigate the links between this variation and multiple parent and offspring traits. Results suggest that there was a genetic basis to parental feeding capacity and offspring solicitation ability, as I found a variation in post-hatching food feeding among populations. I also clarified how this variation is linked to the interrelationships among multiple traits on feeding amount. Variation in investment is particularly important for evolution, and these findings will help us understand the evolution of offspring rearing behavior.首都大学東京, 2019-03-25, 修士（理学）首都大学東

Backdoor attacks to deep neural network-based system for COVID-19 detection from chest X-ray images

Open-source deep neural networks (DNNs) for medical imaging are significant in emergent situations, such as during the pandemic of the 2019 novel coronavirus disease (COVID-19), since they accelerate the development of high-performance DNN-based systems. However, adversarial attacks are not negligible during open-source development. Since DNNs are used as computer-aided systems for COVID-19 screening from radiography images, we investigated the vulnerability of the COVID-Net model, a representative open-source DNN for COVID-19 detection from chest X-ray images to backdoor attacks that modify DNN models and cause their misclassification when a specific trigger input is added. The results showed that backdoors for both non-targeted attacks, for which DNNs classify inputs into incorrect labels, and targeted attacks, for which DNNs classify inputs into a specific target class, could be established in the COVID-Net model using a small trigger and small fraction of training data. Moreover, the backdoors were effective for models fine-tuned from the backdoored COVID-Net models, although the performance of non-targeted attacks was limited. This indicated that backdoored models could be spread via fine-tuning (thereby becoming a significant security threat). The findings showed that emphasis is required on open-source development and practical applications of DNNs for COVID-19 detection