Japan Coast Guard Academy

output

20042025

most citedTameness of definably complete locally o-minimal structures and definable bounded multiplication

10 citations

researchers with a paper here

Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.

collaborating institutions

15 papers

math.CV2025

Indefinite structure of the Bergman kernel on the open unit disk

Kenta Kojin, Shuhei Kuwahara, Michio Seto

In this paper, we focus on an indefinite structure lying behind the Bergman kernel on the open unit disk. In particular, an invariant distance, birational maps and an indefinite ke…

math.LO2024

Lipchitz curve selection and its application to Thamrongthanyalak's open problem

Masato Fujita

We solve an open problem posed in Thamrongthanyalak's paper on the definable Banach fixed point property. A Lipschitz curve selection is a key of our solution. In addition, we show…

math.AC2023

Quasi-quadratic modules in pseudo-valuation domain

Masato Fujita, Masaru Kageyama

We study quasi-quadratic modules in a pseudo-valuation domain $A$ whose strict units admit a square root. Let $X_{R}^{N}$ denote the set of quasi-quadratic modules in an $R$ -…

math.LO2023★ 1 cited

Definable compactness in definably complete locally o-minimal structures

Masato Fujita

We demonstrate that Andújar Guerrero, Thomas and Walsberg's results on definable compactness in o-minimal structures still hold true in definably complete locally o-minimal structu…

math.LO2022

Definable quotients in locally o-minimal structures

Masato Fujita, Tomohiro Kawakami

Let $F = (F, + . \cdot, <, 0, 1, \dots)$ be a definably complete locally o-minimal expansion of an ordered field. We demonstrate the existence of definable quotients of defin…

math.LO2022★ 2 cited

Notes on definably complete locally o-minimal expansions of ordered groups

Masato Fujita

We study definably complete locally o-minimal expansions of ordered groups in this paper. A definable continuous function defined on a closed, bounded and definable set behave like…

math.LO2021

Locally o-minimal open core

Masato Fujita

We demonstrate that the open core of a definably complete expansion of a densely linearly ordered abelian group is locally o-minimal if and only if any definable closed subset of $…

math.LO2021★ 10 cited

Tameness of definably complete locally o-minimal structures and definable bounded multiplication

Masato Fujita, Tomohiro Kawakami, Wataru Komine

We first show that the projection image of a discrete definable set is again discrete for an arbitrary definably complete locally o-minimal structure. This fact together with the r…

math.LO2021★ 5 cited

Almost o-minimal structures and $X$ -structures

Masato Fujita

We propose new structures called almost o-minimal structures and $X$ -structures. The former is a first-order expansion of a dense linear order without endpoints such that…

math.LO2020

Definable Tietze extension property in o-minimal expansion of ordered group

Masato Fujita

The following two assertions are equivalent for an o-minimal expansion of an ordered group $M = (M, <, +, 0, \dots)$ . There exists a definable bijection between a bounded inter…

math.AC2020★ 1 cited

Quasi-quadratic modules in valuation ring and valued field

Masato Fujita, Masaru Kageyama

This is a revised version of the previous version with a new appendix consisting of characteristic two case. We define quasi-quadratic modules in a commutative ring generalizing th…

math.LO2020★ 2 cited

Uniformly locally o-minimal open core

Masato Fujita

This paper discusses sufficient conditions for a definably complete densely linearly ordered expansion of an abelian group having the uniformly locally o-minimal open cores of the…

math.LO2020

Closure and Connected Component of a Planar Global Semianalytic Set Defined by Analytic Functions Definable in O-minimal Structure

Masato Fujita

We consider a global semianalytic set defined by real analytic functions definable in an o-minimal structure. When the o-minimal structure is polynomially bounded, we show that the…

math.LO2020★ 10 cited

Dimension inequality for a definably complete uniformly locally o-minimal structure of the second kind

Masato Fujita

Consider a definably complete uniformly locally o-minimal expansion of the second kind of a densely linearly ordered abelian group. Let $f : X \to R^{n}$ be a definable map, wh…

physics.plasm-ph2004

Numerical Study of Two-fluid Flowing Equilibria of Helicity-driven Spherical Torus Plasmas

T. Kanki, M. Nagata, T. Uyama

Two-fluid flowing equilibrium configurations of a helicity-driven spherical torus (HD-ST) are numerically determined by using the combination of the finite difference and the bound…

Indefinite structure of the Bergman kernel on the open unit disk

Lipchitz curve selection and its application to Thamrongthanyalak's open problem

Quasi-quadratic modules in pseudo-valuation domain

Definable compactness in definably complete locally o-minimal structures

Definable quotients in locally o-minimal structures

Notes on definably complete locally o-minimal expansions of ordered groups

Locally o-minimal open core

Tameness of definably complete locally o-minimal structures and definable bounded multiplication

Almost o-minimal structures and X-structures

Definable Tietze extension property in o-minimal expansion of ordered group

Quasi-quadratic modules in valuation ring and valued field

Uniformly locally o-minimal open core

Closure and Connected Component of a Planar Global Semianalytic Set Defined by Analytic Functions Definable in O-minimal Structure

Dimension inequality for a definably complete uniformly locally o-minimal structure of the second kind

Numerical Study of Two-fluid Flowing Equilibria of Helicity-driven Spherical Torus Plasmas

Almost o-minimal structures and $X$ -structures