Details of the Researcher

PHOTO

Yuji Ando
Section
Mathematical Science Center for Co-creative Society
Job title
Assistant Professor
Degree

  • 博士（理学）（筑波大学）

  • 修士（理学）（日本大学）

Research History 3

  • 2024/12 - Present
    Tohoku University　Mathematical Science Center for Co-creative Society　Assistant Professor

  • 2024/04 - 2024/11
    National Institute of Advanced Industrial Science and Technology　Global Research and Development Center for Business by Quantum-AI technology　Postdoctoral Research Fellow

  • 2024/04 - 2024/09
    Japan International University　Part-time lecturer

Education 3

  • University of Tsukuba　Degree Programs in Pure and Applied Sciences, Graduate School of Science and Technology　Doctoral Program in Physics

    2021/04 - 2024/03

  • Nihon University　Graduate School of Science and Technology　Department of Physics

    2019/04 - 2021/03

  • Nihon University　College of Science and Technology　Department of Physics

    2015/04 - 2019/03

Professional Memberships 2

  • Japan Particle and Nuclear Theory Forum

    2024/05 - Present

  • The Physical Society of Japan

    2015/07 - Present

Research Areas 1

  • Natural sciences / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics /

Awards 2

  1. The Dean’s Award from Graduate School of Science and Technology

    2024/03　Degree Programs in Pure and Applied Sciences Graduate School of Science and Technology University of Tsukuba

  2. 優秀発表賞

    2023/08　Young Nuclear and Particle Physicist Group of Japan

Papers 6

  1. Fast-forward Scaling Theory for Quantum Dynamics on Curved Space-time Peer-reviewed

    Yuji Ando, Shumpei Masuda

    Journal of the Physical Society of Japan　94　(9)　094002　2025/09/15

    Publisher: Physical Society of Japan

    DOI： 10.7566/jpsj.94.094002 　 10.48550/arXiv.2410.02235 　

    ISSN： 0031-9015

    eISSN： 1347-4073

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    Scaling properties inherent in quantum dynamics have been studied for various systems in terms of acceleration, deceleration and time reversing. We show a scaling property of quantum dynamics on curved space-time where gravity plays an essential role. We derive system parameters which realize speed-controlled dynamics. Moreover, we consider spatial scaling and derive system parameters which realize spatially-scaled quantum dynamics.

  2. Closed string amplitudes around tachyon vacuum solution in Kaku theory International-journal Peer-reviewed

    Yuji Ando

    Journal of High Energy Physics　04　029-029　2025/04/02

    Publisher: Springer Nature

    DOI： 10.1007/JHEP04(2025)029 　 10.48550/arXiv.2310.14308 　

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    We incorporate closed string field into Kaku's open string field theory which is defined by using Kaku vertex, and we construct open-closed string field theory. To do this, we define new consistent open-closed vertex and open-open-closed vertex with the Kaku vertex. Because these vertices depend on Chan-Paton parameter such as the Kaku vertex, the open-closed string field theory action that we construct depends on the Chan-Paton parameter such as the Kaku's theory action. However, we can show that an infinitesimal change of $l$ corresponds to a field redefinition. Furthermore, we compute closed string amplitudes around tachyon vacuum solution in this theory. As a result, we confirm that these are conventional pure closed string amplitudes on surfaces without boundaries.

  3. A Consistent Light-Cone-Gauge Superstring Field Theory International-journal Peer-reviewed

    Yuji Ando, Ryota Fujii, Hiroshi Kunitomo, Jojiro Totsuka-Yoshinaka

    Progress of Theoretical and Experimental Physics　2025　(3)　033B02　2025/02/03

    Publisher: Oxford University Press (OUP)

    DOI： 10.1093/ptep/ptaf021 　 10.48550/arXiv.2411.19570 　

    eISSN： 2050-3911

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    Extending a recent development in the bosonic string field theory, we construct a map from the Witten-type gauge-invariant superstring field theory based on an A∞ structure to a light-cone-gauge superstring field theory via two intermediate theories, which we call the Kaku-type and Kugo-Zwiebach-type superstring field theories. We find that a naive extension only gives us an inconsistent light-cone-gauge theory that suffers from the well-known problem caused by divergence due to collisions of local operators. However, we also find that this difficulty may be resolved by considering the stubbed theory and propose it as a consistent light-cone-gauge superstring field theory. The result possibly gives a proof of the unitarity of the Witten-type superstring field theory.

  4. Energy from Ellwood invariant for solutions involving $X^0$ variables International-journal Peer-reviewed

    Yuji Ando, Tomoya Suda

    The European Physical Journal C　84　(6)　578-578　2024/06/06

    Publisher: Springer Nature

    DOI： 10.1140/epjc/s10052-024-12888-2 　 10.48550/arXiv.2303.13789 　

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    For some classical solutions $\Psi_\mathrm{sol}$ in Witten's bosonic string field theory, it was proven that energy of the solution is proportional to the Ellwood invariant $\mathrm{Tr}(\mathcal{V}\Psi_\mathrm{sol})$ with $\mathcal{V}=c\bar{c}\partial X^0\bar{\partial}X^0$. We examine the relation for solutions involving $X^0$ variables. As a result, we obtain that the relation may not hold for such solutions. Namely, there is a possibility that the energy is not proportional to the Ellwood invariant.

  5. The classical solutions with $k_-=0$ in Kaku theory International-journal Peer-reviewed

    Yuji Ando

    Progress of Theoretical and Experimental Physics　2023　(6)　063B02　2023/05/31

    Publisher: Oxford University Press (OUP)

    DOI： 10.1093/ptep/ptad069 　 10.48550/arXiv.2302.03928 　

    eISSN： 2050-3911

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    We consider Kaku theory as introduced in M. Kaku, Phys. Lett. B 200, 22 (1988) and investigate classical solutions. In particular, we obtain that the equation of motion with the restriction $k_-=0$ in the Kaku theory is equivalent to the equation of motion in Witten theory. Because of this property, some solutions including the tachyon vacuum solution in the Witten theory satisfy also the equation of motion in the Kaku theory. In addition, we confirm that the cohomology around the tachyon vacuum solution is trivial also in the Kaku theory.

  6. Intertwining solutions with general reference D-branes and multi-brane solutions

    Yuji Ando

    2021/03

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Misc. 5

  1. Fast-forward scaling theory for quantum dynamics on curved space-time

    Yuji Ando, Shumpei Masuda

    Meeting Abstracts of the Physical Society of Japan　80　(1)　2025/03

    Publisher: The Physical Society of Japan

  2. Time control for quantum systems by using general relativity

    P-115　2025/01

  3. Field redifinition berween Witten and Kugo-Zwiebach superstring field theory

    Yuji Ando, Ryota Fujii, Hiroshi Kunitomo, Jojiro Yoshinaka

    Meeting Abstracts of the Physical Society of Japan　78　(2)　2023/09

    Publisher: The Physical Society of Japan

  4. Closed string amplitudes around tachyon vacuum solution in Kaku theory

    Yuji Ando

    Meeting Abstracts of the Physical Society of Japan　78　(2)　2023/09

    Publisher: The Physical Society of Japan

  5. Intertwining field and boundary condition in Witten's bosonic open string field theory

    Yuji Ando, Akitsugu Miwa

    O-18　2020/12/02

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    A formulation of the open string field theory requires us to choose a boundary condition．It is one of open problems, which is called the background independence．Recently，the intertwining field is suggested by Erler and Maccaferri [1]．It enables us to change boundary conditions and is expected to give a proof of the background independence．In this talk，we review the intertwining field and how to construct it by using the flag state [2]．

Presentations 21

  1. Why do string field theorists passionately study homotopy algebra? Invited

    Yuji Ando

    Meeting for Intersections of Nuclear and Other Researches　2024/03/08

  2. Closed string amplitudes around tachyon vacuum solution in Kaku's bosonic string field theory Invited

    Yuji Ando

    2023/12/15

  3. Closed string amplitudes around tachyon vacuum solution in Kaku's bosonic string field theory Invited

    Yuji Ando

    2023/10/05

  4. Fast-forward scaling theory for quantum dynamics on curved space-time

    Yuji Ando, Shumpei Masuda

    JPS 2025 Spring Meeting　2025/03/21

  5. Time control for quantum systems by using general relativity

    2025/01/23

  6. Relation between covariant and light-cone superstring field theory International-presentation

    Yuji Ando, Ryota Fujii, Hiroshi Kunitomo, Jojiro Yoshinaka

    KEK Theory Workshop 2023　2023/11/29

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    In perturbative string theory, there have mainly been two ways to quantize the string. Either one quantizes in lightcone gauge, or one quantizes covariantly. The difference between them is only gauge condition, and the equivalence of on-shell amplitudes had been already shown. String field theory is a candidate for a non-perturbative formulation of string theory. There have mainly been two formulations, they are covariant string field theory (covariant SFT) and light-cone string field theory (light-cone bosonic SFT) In bosonic string field theory, it is shown that the light-cone bosonic SFT is an effective SFT which is obtained by integrating out some degrees of freedom from a covariant bosonic SFT by Erler-Matsunaga. We show that the light-cone super SFT is an effective SFT for a covariant super SFT. This talk is based on the collaboration with R.Fujii, H.Kunitomo and J.Yoshinaka.

  7. Field redifinition berween Witten and Kugo-Zwiebach superstring field theory

    Yuji Ando, Ryota Fujii, Hiroshi Kunitomo, Jojiro Yoshinaka

    JPS 78th Annual Meeting　2023/09/18

  8. Derivation of similarity transformation from light-cone BRST charge to RNS BRST charge

    Ryota Fujii, Yuji Ando, Hiroshi Kunitomo, Jojiro Yoshinaka

    JPS 78th Annual Meeting　2023/09/18

  9. Closed string amplitudes around tachyon vacuum solution in Kaku theory

    Yuji Ando

    JPS 78th Annual Meeting　2023/09/16

  10. Quantum Field Theory and Homotopy Algebra

    Yuji Ando

    69th YONUPA Summer School　2023/08/19

  11. Open-closed string field theory using Kaku vertex

    Yuji Ando

    Strings and Fields 2023　2023/08/04

  12. Closed string amplitudes around tachyon vacuum solution in Kaku's bosonic string field theory Invited

    Yuji Ando

    2023/07/11

  13. Recent developments of string field theory Invited

    Yuji Ando

    2023/06/27

  14. Closed string amplitudes around tachyon vacuum solution in Kaku's bosonic string field theory Invited

    Yuji Ando

    2023/05/12

  15. The open-closed string field theory using the Kaku vertex

    Yuji Ando

    JPS 2023 Spring Meeting　2023/03/23

  16. Open bosonic string field theory with weak $A_\infty$ structure using Keku vertex

    Yuji Ando

    68th YONUPA Summer School　2022/08/09

  17. The classical solution in Kaku model

    Yuji Ando

    JPS 77th Annual Meeting　2022/03/17

  18. Perturbative vacuum solution using flag state

    Yuji Ando

    67th YONUPA Summer School　2021/08/08

  19. Intertwining solutions with general reference D branes

    Yuji Ando

    JPS 76th Annual Meeting　2021/03/13

  20. Intertwining solution in Witten's bosonic string field theory (review)

    Yuji Ando

    2020/08/28

  21. Intertwining field and boundary condition in Witten's bosonic open string field theory

    Yuji Ando, Akitsugu Miwa

    2020/12/02

    More details Close

    A formulation of the open string field theory requires us to choose a boundary condition．It is one of open problems, which is called the background independence．Recently，the intertwining field is suggested by Erler and Maccaferri \cite{Erler:2014eqa}．It enables us to change boundary conditions and is expected to give a proof of the background independence．In this talk，we review the intertwining field and how to construct it by using the flag state \cite{Erler:2019fye}．

Show all Show first 5

Research Projects 2

  1. 弦の場の理論における開弦-開弦双対性と指導原理 Other

    Yuji Ando

    Offer Organization: Japan Science and Technology Agency

    System: The establishment of university fellowships towards the creation of science technology innovation

    Institution: University of Tsukuba

    2022/04 - 2024/03

  2. 弦の場の理論における開弦-開弦双対性と指導原理 Other

    Yuji Ando

    Offer Organization: Ministry of Education, Culture, Sports, Science and Technology

    System: The establishment of university fellowships towards the creation of science technology innovation

    Institution: University of Tsukuba

    2021/04 - 2022/03

Teaching Experience 3

  1. g-RIPS-Sendai, MITSUBISHI-B Project, academic mentor　Tohoku University Other

  2. 数学②　Japan International University Undergraduate (liberal arts)

  3. 数学①　Japan International University Undergraduate (liberal arts)

Academic Activities 2

  1. The coordinator of Career Forum in the 70th YONUPA Summer School

    National Olympics Memorial Youth Center

    2024/08/21 - 2024/08/25

    Activity type: Academic society, research group, etc.

  2. The organizer of the 68th YONUPA Summer School

    online

    2022/08/06 - 2022/08/09

    Activity type: Academic society, research group, etc.