The effect of varying sound velocity on primordial curvature perturbations

We study the effects of sudden change in the sound velocity on primordial curvature perturbation spectrum in inflationary cosmology, assuming that the background evolution satisfies the slow-roll condition throughout. It is found that the power spectrum acquires oscillating features which are determined by the ratio of the sound speed before and after the transition and the wavenumeber which crosses the sound horizon at the transition, and their analytic expression is given. In some values of those parameters, the oscillating primordial power spectrum can better fit the observed Cosmic Microwave Background temperature anisotropy power spectrum than the simple power-law power spectrum, although introduction of such a new degree of freedom is not justified in the context of Akaike's Information Criterion.Comment: 12 pages, 3 figures; references added; appendix modifie

The transient experience of living in cities: focusing on the instability of Japanese-Filipinos in Toyooka City, Hyogo Prefecture, Japan

The 13th Next-Generation Global WorkshopThis paper is part of the output of the Toyooka City-Kobe University joint research project "Gaikokujin jumin ni kan suru chosa kenkyu [Research on Foreign Residents]", conducted in 2019. This paper is an English translation of [Saito, Y. (2021). [Forthcoming]. The domestic migration of Japanese-Filipinos after migration to Japan: the case of Toyooka City, Hyogo Prefecture. Sociological Review of Kobe University, 38.], with modifications and additional information.第13回次世代グローバルワークショップテーマ: New Risks and Resilience in Asian Societies and the World 日程: 21-23 November, 2020 開催場所: ベトナム社会科学院(ハノイ)/Vietnam Academy of Social Sciences(No. 1 Lieu Giai street, Ba Dinh, Hanoi, Vietnam) ※Due to the COVID-19, the workshop will be held at ONLINE for overseas participants(not from Vietnam)/ONSITE for Vietnamese participants.This paper sheds light on the domestic movement of Japanese-Filipinos after migrating to Japan, focusing in particular on Japanese-Filipinos living in Toyooka City, Hyogo Prefecture. This study examines the movement of Japanese-Filipinos by taking the perspective that their current place of residence is one part of a process of internal migration. The Filipino population has fluctuated significantly since 2017, indicating that residents are coming and going rapidly, a phenomenon closely related to changes in the Japanese-Filipino population. Most Japanese-Filipinos have moved in as a result of internal migration related to employment opportunities, mediated by a particular temporary employment agency which provides jobs to them working in factories, in addition to giving a large amount of support in both work and housing. As such, the relationship between Japanese-Filipinos and the agency is one of dependency. At the same time, however, the forced renewal of their working contracts every few months makes it difficult for them to have a long-term outlook, causing serious problems for families with children of school age. The migratory trends of Japanese-Filipinos seen in Toyooka City suggest that they are likely to stay as long as their employment contract lasts. At the same time, however, when their employment contract ends, they are compelled to move to another city or region because the choice of recruitment agencies for foreigners is limited. Previous experiences of domestic migration highlight the possibility of future replacement. These characteristics suggest that Japanese-Filipinos have chosen to settle in Japan under conditions of instability, repeatedly moving around the country. At the root of this instability and mobility might be the kind of environment in which Japanese-Filipinos are able to make a living on their own. The movement patterns of Japanese-Filipinos, not settling in one city but moving from place to place, show that it is important to follow their migration as a "line", that is, as an ongoing linear sequence of movements, in order to help clarify the way of life of Japanese-Filipinos in Japan

Defining relations of 3-dimensional cubic AS-regular algebras of Type P, S and T

Classification of AS-regular algebras is one of the most important projects in noncommutative algebraic geometry. Recently, Itaba and the first author gave a complete list of defining relations of $3$-dimensional quadratic AS-regular algebras by using the notion of geometric algebra and twisted superpotential. In this paper, we extend the notion of geometric algebra to cubic algebras, and give a geometric condition for isomorphism and graded Morita equivalence. One of the main results is a complete list of defining relations of $3$-dimensional cubic AS-regular algebras corresponding to $\mathbb{P}^1 \times \mathbb{P}^1$ or a union of irreducible divisors of bidegree $(1,1)$ in $\mathbb{P}^1 \times \mathbb{P}^1$. Moreover, we classify them up to isomorphism and up to graded Morita equivalence in terms of their defining relations.Comment: 20 pages, 2 table

Optimal prestressing of triple-bay prestressed stayed columns

A nonlinear finite element model of a triple-bay prestressed stayed column is developed within the commercial package ABAQUS. A linearly obtained 'optimal prestressing force' that maximizes the critical buckling load is investigated since this quantity has been demonstrated in previous work on single-bay prestressed columns to provide a lower bound to the actual maximum load carrying capacity when compared to experimental results and nonlinear modelling. The ratio of the crossarm to the overall column length, the diameter of the cable stays, the relative lengths of the individual crossarms and the ratio of the initial prestressing force to the aforementioned linear optimal prestress are varied. Measures for the relative efficiency of the main column and the stays are defined and the objective of the optimization study is for the efficiency to be maximized. It is found that the true optimal prestress is generally higher than the equivalent, linearly obtained, quantity but by a significantly reduced factor when compared to an equivalent study for single-bay prestressed stayed columns