Updated on 2023/11/12

写真a

 
AIZAWA Hiroki
 
Organization
Faculty of Science and Engineering Research Associate
Contact information
The inquiry by e-mail is 《here
External link

Degree

  • 博士(学術) ( 東北大学 )

  • 修士(工学) ( 東北大学 )

Education

  • 2023.3
     

    Tohoku University   doctor course   completed

  • 2020.3
     

    Tohoku University   master course   completed

  • 2018.3
     

    Tohoku University   graduated

Research History

  • 2023.4 - Now

    Chuo University   Faculty of Science and Engineering Department of Civil and Environmental Engineering   Assistant Professor

Professional Memberships

  • 日本経済学会

  • 土木学会

  • 応用地域学会

Research Areas

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Civil engineering plan and transportation engineering

Papers

  • Satellite City Formation for a Spatial Economic Model: Bifurcation Mechanism in a Hexagonal Domain

    Hiroki Aizawa, Kiyohiro Ikeda, Yosuke Kogure

    Networks and Spatial Economics   23 ( 3 )   529 - 558   2023

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    Publishing type:Research paper (scientific journal)  

    The economic agglomeration of one large city surrounded by satellite cities is observed worldwide and is a topic of keen economic interest. We theoretically investigate where such satellite cities emerge in a two-dimensional economic space in which discrete locations are evenly distributed in a regular-hexagonal domain. To elucidate this emergence, we introduce two viewpoints: (1) the bifurcation mechanism of the full agglomeration at the geographical center in this domain (mono-center), which produces satellite cities around this center, and (2) the existence of invariant patterns, which are equilibria for any value of the transport cost parameter. Theoretically-predicted agglomeration patterns are ensured to exist as stable equilibria for a spatial economic model proposed by Forslid and Ottaviano (2003). We theoretically find one large central city surrounded by hexagonal satellite cities that is a two-dimensional counterpart of the core-periphery pattern (Krugman 1991). Moreover, we demonstrate that spatial patterns of twin cities, three cities, and racetrack cities are absorbed into the mono-center as the transport cost decreases. These transitions are ubiquitously observed in the two-dimensional spatial platform with the geographical center.

    DOI: 10.1007/s11067-023-09586-z

    Scopus

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  • Group-Theoretic Bifurcation Mechanism of Economic Agglomerations on a Square Lattice

    Y. Kogure, K. Ikeda, H. Aizawa

    International Journal of Bifurcation and Chaos   31 ( 13 )   2021.10

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    Publishing type:Research paper (scientific journal)   Publisher:World Scientific Pub Co Pte Ltd  

    We elucidate the mechanism of the self-organization of square agglomeration patterns that are described by spatial economic models on a square lattice with periodic boundary conditions. Focusing on the symmetry of the square lattice, we conduct a group-theoretic analysis and obtain bifurcating patterns from the uniform distribution. Furthermore, for the replicator dynamics, which are widely used in economics, we pay attention to the existence of invariant patterns that are solutions to the governing equation for any value of the bifurcation parameter (the trade freeness for spatial economic models). We advance invariant patterns on the square lattice as candidates of stable equilibria. Using a prototype spatial economic model proposed by Forslid and Ottaviano [2003], we numerically show a tendency that bifurcating solutions arrive at invariant patterns after bifurcation. This tendency is advanced as the underlying mechanism of the progress of economic agglomerations that is to be considered in the study of spatial economic agglomerations.

    DOI: 10.1142/s0218127421300408

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  • Breaking and Sustaining Bifurcations in SN-Invariant Equidistant Economy

    H. Aizawa, K. Ikeda, M. Osawa, J. M. Gaspar

    International Journal of Bifurcation and Chaos   30 ( 16 )   2050240 - 2050240   2020.12

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    Publishing type:Research paper (scientific journal)   Publisher:World Scientific Pub Co Pte Lt  

    This paper elucidates the bifurcation mechanism of an equidistant economy in spatial economics. To this end, we derive the rules of secondary and further bifurcations as a major theoretical contribution of this paper. Then we combine them with pre-existing results of direct bifurcation of the symmetric group [Formula: see text] [Elmhirst, 2004]. Particular attention is devoted to the existence of invariant solutions which retain their spatial distributions when the value of the bifurcation parameter changes. Invariant patterns of an equidistant economy under the replicator dynamics are obtained. The mechanism of bifurcations from these patterns is elucidated. The stability of bifurcating branches is analyzed to demonstrate that most of them are unstable immediately after bifurcation. Numerical analysis of spatial economic models confirms that almost all bifurcating branches are unstable. Direct bifurcating curves connect the curves of invariant solutions, thereby creating a mesh-like network, which appears as threads of warp and weft. The theoretical bifurcation mechanism and numerical examples of networks advanced herein might be of great assistance in the study of spatial economics.

    DOI: 10.1142/s0218127420502405

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  • BIFURCATION ANALYSIS OF MONOCENTRIC AGGLOMERATION ON A LONG NARROW ECONOMY

    Hiroki AIZAWA, Kiyohiro IKEDA, Yosuke KOGURE, Minoru OSAWA, José Maria GASPAR

    Journal of Japan Society of Civil Engineers, Ser. D3 (Infrastructure Planning and Management)   76 ( 4 )   282 - 298   2020

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    Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Civil Engineers  

    DOI: 10.2208/jscejipm.76.4_282

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  • Invariant Patterns for Replicator Dynamics on a Hexagonal Lattice

    K. Ikeda, Y. Kogure, H. Aizawa, Y. Takayama

    International Journal of Bifurcation and Chaos   29 ( 06 )   1930014 - 1930014   2019.6

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    Publishing type:Research paper (scientific journal)   Publisher:World Scientific Pub Co Pte Lt  

    A hexagonal lattice is a promising and plausible spatial platform for economic agglomeration in spatial economic models. This paper aims at the elucidation of agglomeration mechanisms for the replicator dynamics on this lattice. Attention is paid to the existence of invariant solutions that retain their spatial patterns when the bifurcation parameter changes. Such existence is a special feature of the replicator dynamics, which is widely used in economics. A theoretical procedure to find invariant patterns is proposed and possible invariant patterns are advanced and classified. Among a plethora of theoretically possible invariant patterns, those which actually become stable for a spatial economic model are investigated numerically. The major finding of this paper, is the demonstration of equilibrium curves of invariant patterns that are connected by those of noninvariant ones to form a complicated mesh-like structure, just like the threads of warp and weft. It would be an important scientific mission to elucidate the mechanism of this complicated structure, and contribute to the study in economic geography.

    DOI: 10.1142/s0218127419300143

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  • Stability of Bifurcating Patterns of Spatial Economy Models on a Hexagonal Lattice

    K. Ikeda, H. Aizawa, Y. Kogure, Y. Takayama

    International Journal of Bifurcation and Chaos   28 ( 11 )   1850138 - 1850138   2018.10

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    Publishing type:Research paper (scientific journal)   Publisher:World Scientific Pub Co Pte Lt  

    Self-organization of spatial patterns is investigated for a scalar field of a system of locations on a hexagonal lattice. Group-theoretic bifurcation analysis is conducted to exhaustively try and find possible bifurcating patterns. All these patterns are proved to be asymptotically unstable for general spatial economic models in new economic geography. Microeconomic interactions among the locations are expressed by a spatial economy model and all bifurcating patterns are demonstrated to be unstable by numerical bifurcation analysis.

    DOI: 10.1142/s0218127418501389

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Awards

  • 2022年度応用地域学会 最優秀学生論文賞

    2022.12   応用地域学会   How should place-based policies be designed for efficiently promoting retail agglomeration?

    相澤大輝,河野達仁

Research Projects

  • 競争形態と集積メカニズムに基づく地域産業政策の厚生分析:産業空間分布と市場の失敗

    Grant number:23K18790  2023.8 - 2025.3

    日本学術振興会  科学研究費助成事業  研究活動スタート支援  中央大学

    相澤 大輝

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    Grant amount: \1300000 ( Direct Cost: \1000000 、 Indirect Cost: \300000 )

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  • 多様な財供給を行う供給者と家計の二次元空間立地に関する分岐解析と均衡の厚生分析

    Grant number:21J15651  2021.4 - 2023.3

    日本学術振興会  科学研究費助成事業  特別研究員奨励費  東北大学

    相澤 大輝

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    Grant amount: \900000 ( Direct Cost: \900000 )

    (分析1)小売店の独占的競争を基礎とする商業集積モデル (Tabuchi, JUE2009) と,実空間の道路ネットワーク(放射線と環状線から形成される道路ネットワーク)を統合した商業集積モデルを構築した.このモデルを用いて,道路整備が商業集積へ与える影響を分析した.その結果,道路整備の結果として創発する商業集積の地理的配置は,道路整備順序に依存するという結論を得ている.さらに,厚生の観点で最適な商業集積が,道路整備の結果として創発する商業集積とは異なるという結論も得ている.前者の結果は,厚生を上昇させるという観点では,道路整備順序の考慮が必要であることを示唆する.一方,後者の結果は,最適な商業集積を実現するためには,商業集積の地理的配置を操作する政策(e.g., 立地規制)が必要であることを示唆する.
    (分析2)小売店の独占的競争と内生的な消費者立地を基礎とする商業集積モデルを構築した.従来,小売店の立地と内生的な消費者立地を同時に考慮した研究はあまりなく,Fujita and Thisse (RES1986), Fujita (RSUE1988), Liu and Fujita (ARS1991) などに限られる.これらの先行研究とは異なる本研究の着眼点の一つは,所得移転がもたらす厚生への影響である.このモデルを用いて,小売店への所得補助や消費者間の所得移転がもたらす厚生への影響を分析した. その結果,小売店への所得補助政策の導入は厚生を上昇させるものの,家計間の所得移転の導入は厚生を低下させるという結論を得た.さらに,市場均衡において,小売店の店舗数は最適ではないものの,消費者の立地だけに限定した場合,市場均衡は局所的に最適であるという結論を得た.この結論は,家計間の所得移転だけでなく消費者の立地規制の導入も厚生を低下させることを示唆する.

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Allotted class

  • 2023   プログラミング言語1   Department

Teaching Experience

  • プログラミング言語1

    2023.4 - Now   Institution:中央大学