I am Nori Iizuka, a theoretical physicist currently working at National Tsing Hua University, Taiwan, and at Yukawa Institute, Kyoto University, Japan. I am researching theoretical and mathematical physics, especially *string theory*.
Extremely simply put, string theory is a theory of strings, where we regard all (apparently point-like) particles made up by vibrating one-dimensional strings. Quite remarkably, by making this theory of vibrating strings mathematically completely consistent with the principles of quantum mechanics and (1+1)-dimensional general relativity, you are forced to see an ultimate theory of theoretical physics, which contains higher dimensional gravity (i.e., Einstein's general relativity), weak force, strong force, extra dimensions (meaning that our space-time has more than 3 spatial directions!), supersymmetry, black holes (space-time regions where gravitational force is so strong that nobody, even a light beam cannot escape from that at least classically), wormholes (a space-time structure where different points are connected), emergent space-time and holography (These are very modern physics so I will explain it more later), and many beautiful mathematics. String theory is an extremely rich and deep subject!

Among all, the most interesting aspect of string theory to me is its gravitational aspects, namely, string theory as a theory of *quantum gravity*, an ultimate theory to describe Einstein's theory of gravity and space-time according to the principles of quantum mechanics. My past research achievements were to shed new light on the aspects of quantum gravity and space-time, including finding new attractor mechanisms for black holes and also finding a new model of quantum black holes clarifying the 'mistakes' of Stephen Hawking's black hole evaporation.

In this homepage, I would like to explain briefly what these theories are and why we theoretical physicists are working on these so hard. For experts who is currently working on these and possibly seeking for the post-doc position, I would also like to explain what kind of stuff especially in string theory I am working on. But of course, if you are beginning undergrad student or advanced high school student, I am sure that you do not know what these theories are, but that's also completely OK! I will also explain these for much simpler ways and as intuitive as possible. If you are in the 3rd year on your undergrad study and seeking for your future research directions, my homepage might help you to understand why string theory and quantum gravity is such an exciting field and you youngsters should think of challenging it.

I would also like to show some useful information about international workshops or my talk slide about recent developments in this homepage as well. In such ways, I hope my homepage becomes useful for various level of people, high school students/undergrad university students/Ph.D. students/postdoc/senior faculties. Hope you enjoy this new homepage!

私は理論物理学者で、2025年現在、国立清華大学及び京都大学基礎物理学研究所で理論物理、数理物理、特に「弦理論」について研究しています。

弦理論って何？と思う人も多いと思います。ものすごく簡単に言えば、弦理論というのはこの世を構成する「素粒子」が、大きさのない点ではなく、弦楽器の弦の様にある長さをもった「ひも／弦」だと考える理論です。もちろん、この素粒子が「ひも／弦」のような構造でできているという実験証拠は、現在までの実験では一切確認されていません。故にあくまで素粒子が「ひも／弦」であるというのは単なる仮説に過ぎません。またもし本当に素粒子が「ひも／弦」であると考えるにしても、このひもの大きさは現代の実験では見えないぐらい小さな小さな大きさであると考えないといけません。

ではなぜそんな実験証拠もない仮説に基づいた理論に興味があるの？と思うかもしれません。驚くべきことに、この粒子が弦でできているという仮説に基づいて理論を、数学的に完全に（現代物理学の基礎である量子力学と）整合性をつけようとすると、この弦理論は単なる弦の振動を扱う理論にとどまらず、アインシュタインの一般相対性理論やマクスウェルの電磁気学、ベータ崩壊を扱う弱い力や、陽子や中性子を成すクォークの相互作用を扱う強い力、これらを全て含んだある意味究極の理論となってしまうのです！また弦理論は、この世は３次元ではなく他の見えないほど小さな他の次元があることも予言します。このように弦理論は、まだまだ我々の知らない非常に数学的にも豊かな自然現象を内在する理論なのです。故に弦理論は世界中の多くの理論物理学者を魅了し、今の多くの研究者たちが精力的に研究しているのです。　　　

その様な非常に豊かな構造を示す魅力的な弦理論の中でも特に私が興味をもっているのが量子重力理論としての弦理論の側面です。 このホームページでは、私の研究している「弦理論、量子重力理論」について、（高校で物理を勉強しているアドバンスな）高校生向け／（大学で物理を勉強している）大学生向け／実際に弦理論の研究に携わっている大学院生や研究者向けと段階的に様々なレベルで紹介していこうと思っています。

同時に研究会や最新の研究の発展などの情報もアップしていきたいと思いますので弦理論についてよく知りたい方から、将来私と共に弦理論について研究してみたいと考えておられる高校生、大学生、大学院生やポスドクの方について有用なホームページにしていきたいと思っていますのでよろしくお願いします。

~ life is a journey ~

I was born in Kishiwada, a city in the southern part of Osaka Prefecture. After high school, in 1994, I enrolled at the University of Tokyo and graduated in 1998. I then continued in graduate school at the University of Tokyo until the summer of 1999. After that, I moved to New York for my PhD studies at Columbia University. I was extremely fortunate to meet Prof. Daniel Kabat at Columbia, my great mentor and now also a close collaborator. Through many helpful discussions with him, I learned a great deal about string theory, the quantum nature of black holes, and holography during my PhD.

In 2003, I obtained my PhD; the title of my thesis was "Holographic description of quantum black holes and spacetime".

After obtaining my PhD at Columbia, my worldwide postdoc career started. In the summer of 2003, I flew from New York to Mumbai, India, to begin my first postdoc at the Tata Institute for Fundamental Research (TIFR). At the time, I regarded TIFR as one of the leading string theory groups in the world. While I was in India, I was again extremely fortunate to work with many outstanding string theorists, including Prof. Sandip Trivedi (former Director of TIFR (2015–2020) and still a close collaborator), Prof. Atish Dabholkar (Director of ICTP, Trieste), Prof. Ashoke Sen, and many others. I learned a lot of physics and mathematics from them. Working and living in India was also, in my personal opinion, one of the great experiences of my life, and I truly enjoyed it. To be honest, before going to India I hesitated due to my ignorance, but looking back, deciding to go was one of the best decisions in my life. (I traveled widely in India, from Kanyakumari, the southern tip of the Indian subcontinent, to the northern Himalayas, the Ganges, and more. There is a quote by St. Augustine: “The world is a book, and those who do not travel read only one page.” I think that is right.)

In 2006, after a warm farewell to my friends in India and a stopover to visit a good friend in Greece, I moved to the United States again—this time to the West Coast—for my second postdoc at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara. It is a world-famous theoretical physics institute; the Director at that time was Nobel Prize laureate Prof. David Gross. I was again fortunate to work with the late Prof. Joe Polchinski, who discovered D-branes and wrote the famous two-volume textbook on string theory. Together we worked on a toy model of holography (the so-called Iizuka–Polchinski model) and investigated the quantum nature of black holes through this model.

In 2009, I moved to CERN, a major international research center on the France–Switzerland border, as a fellow (a non-member-state fellowship, since Japan is not a CERN member state) and also received a special COFUND fellowship. During my time there, the Large Hadron Collider (LHC) discovered the Higgs boson. In 2012, I moved to the Yukawa Institute, and in 2013 to RIKEN. After 2014, I was based in Osaka for about 10 years, and I am now mainly in Taiwan.

In total, I have spent more than 13 years abroad: 4 years in the US for my PhD, 3 years in India, 3 years in the US as a postdoc, and 3 years in Europe. I am now based in Taiwan. Consequently, in terms of how I do physics, I feel that my approach to physics has been shaped strongly by these international experiences.

After I joined Osaka, I was again fortunate to have many talented young graduate students. To name just a few, Kotaro Tamaoka was one of my first graduate students at Osaka. He is talented and passionate about physics, and he is now an associate professor at Nihon University. I also had another extremely talented graduate student, Takanori Anegawa, who is now a tenured assistant professor at Yonago College. In addition to these, I have had many other talented students. During my time in Osaka, I also worked with talented young collaborators and postdocs. For example, Dr. Sunil Kumar Sake (from TIFR; Sandip’s former student) later moved to the US for his next position (currently a postdoc at UC Santa Cruz), and Dr. Nicolo Zenoni (from Italy) has been a JSPS postdoc. Together with these and other collaborators, we worked hard to understand and unravel the mysteries of gravity, spacetime, and quantum black holes.

Since 2024, I have been mainly based in Taiwan as a faculty member at National Tsing Hua University (NTHU), while also keeping a close connection with Yukawa Institute for Theoretical Physics (YITP), Kyoto University. Living in Taiwan has been a refreshing change for me: the research environment is very international, and I enjoy daily discussions with colleagues and students across different areas of high-energy theory. I am also actively organizing seminars and workshops, and building collaborations in Taiwan and across Asia. In particular, I have postdoctoral collaborators in both locations: Dr. Akihiro Miyata is based in Kyoto, and Dr. Shraiyance Jain is expected to join us in Taiwan as a postdoc.

On the research side, my recent focus is on quantum-information aspects of gravity and holography—especially multipartite entanglement and its geometric meaning (including genuine multi-entropy), black-hole information and evaporation, and related problems in quantum gravity. If you are interested in these topics and would like to collaborate, please feel free to contact me.

大阪生まれ。1994年4月、東京大学理科一類に入学し、1998年3月 東京大学工学部物理工学科を卒業。
同年4月から 東京大学大学院理学系研究科宇宙理論研究室に所属し、初期宇宙論やブラックホールを学びました。

1999年8月から東京大学大学院を休学し（数年後に中退）、渡米してアメリカの コロンビア大学大学院 Department of Physics のPh.D.課程に入学しました。
コロンビア大学では、当時若手教員として新たに着任された Daniel Kabat教授の指導のもと、 弦理論やブラックホールの量子論について多くを学びました。 良き指導教員に出会えたことは、私にとって非常に幸運でした。

2003年8月、コロンビア大学にてPh.D.を取得しました（書類上の卒業は同年10月）。 Ph.D. thesis は「Holographic description of quantum black holes and spacetime」 （日本語訳：ホログラフィーによる量子ブラックホールと時空の記述）です。

2003年9月から、最初のポスドクとしてインドの タタ基礎研究所（TIFR）に着任しました。 Sandip Trivediさん（タタ研究所前所長）や Atish Dabholkarさん（イタリアICTP研究所所長）をはじめ、すばらしい研究者の方々とともに研究できたことは大きな経験でした。 TIFR での研究生活は非常に刺激的で、コロンビア大学での学びとともに、 研究者としての私の原点になっています。

2006年9月からは2回目のポスドクとして、アメリカ・カリフォルニア州サンタバーバラにある Kavli理論物理学研究所（KITP）に着任しました。 今は亡き Joseph Polchinski さんとも共同研究でき、非常に多くを学びました。

2009年9月からは、スイスの CERN（欧州原子核研究機構）にて3回目のポスドクをしました。 Non-member-state fellow（日本はCERNに非加盟国として参加）に加え、 COFUND fellow という特別なフェローシップもいただき、 通常2年のところ3年のポジションとして在籍しました。

2012年9月からは日本に戻り京都大学基礎物理学研究所に着任、2013年9月からは理研にてスタッフ研究員を経て、 2014年から約10年間大阪大学で助教を務めました。2024年からは台湾の 国立清華大学で副教授（日本の准教授に相当）を務めています。 また同時に、京都大学基礎物理学研究所で基研特任准教授も兼任しています。

キャリアの早い時期に海外で13年（アメリカ4年、インド3年、アメリカ3年、ヨーロッパ3年）過ごし、 海外でPh.D.を取得したこともあって、研究のスタイルは日本国内の標準的なスタイルよりも、 国際的な研究環境に近い感覚があると思っています。

大阪大学では何人もの大学院生を指導しました。 中でも、着任してすぐ私の最初の学生になった一人である 玉岡幸太郎君は非常に優秀で、 現在は日本大学で准教授として活躍しています。 また、 姉川尊徳君も非常に優秀で、 Doctor1年目から日本学術振興会特別研究員（DC1）に選ばれ、 Doctor3年時には大阪大学大学院理学研究科優秀研究賞を受賞するなどの成果を上げ、 現在は米子高専で助教として活躍しています。

また海外から多くのポスドクも私の研究室に加わってくれました。インドから Sunil Kumar Sakeさん（Sandipさんの下でPhD）、 イタリアから Nicolo Zenoniさん。お二人とも現在は次のポスドク先に移られています。最近は 宮田晃大さんや、インド出身のShraiyance Jainさん（Abhijitさんの下でPhD）ら若手ポスドクとも共同研究を行っています。

このように才能にあふれた若い学生・ポスドク、そして多くの共同研究者とともに、 量子重力、時空、ブラックホールの謎に迫る研究を進めています。

🔸 Join Us! 加入我們的研究團隊！

From prestigious fellowships to international postdoctoral positions, and permanent faculty placements in Japan, my group has built a track record of diverse and successful career outcomes. So join us!

We are looking for passionate students in theoretical physics (including undergraduate, master’s, and PhD levels).
我們正在招募對理論物理充滿熱情的學生（包含大學部、碩士班、博士班）。

We especially welcome those interested in the following topics: quantum aspects of black holes, holography, entanglement, mathematical physics, and even foundations of AI, large language models, and their relation to physics.
尤其歡迎對以下主題有興趣者：黑洞的量子理論、全息理論、糾纏、數理物理，甚至是人工智能的基礎、大型語言模型以及它們與物理的關聯性。

In particular, we welcome students eager to explore deep physics, questions that probe the foundations of spacetime, quantum information, and the origin of the universe.
特別歡迎對「根本物理」充滿熱情的學生──那些渴望探索時空、量子資訊以及宇宙起源等根本問題的人。

In approaches to quantum gravity beyond Einstein’s general relativity, spacetime is no longer considered fundamental. Instead, it is thought to emerge as an effective description, deeply rooted in the structure of quantum entanglement.
在超越愛因斯坦廣義相對論的量子重力理論中，時空不再被視為基本的實體，而是被認為是一種源自量子糾纏結構的創發性有效描述。

How does spacetime emerge from quantum information?
What governs the physics inside black holes—the most extreme and mysterious corners of the universe?
How did our universe begin, and what lies beyond the classical notion of a beginning?
時空如何從量子資訊中創生？
黑洞內部——這個宇宙中最極端、最神秘的角落——其物理法則是什麼？
我們的宇宙是如何開始的？在傳統「開端」的概念之外，是否還有更深的真相？

If you are fascinated by such fundamental questions, and want to explore deep physics that challenges the foundations of space, time, and reality itself— we invite you to join us.
如果你對這些根本性的問題感到著迷，並渴望挑戰空間、時間與實在本身的基礎， 我們誠摯邀請你加入我們的研究。

Please write your email in English, since I can not speak Chinese. However, note that this opportunity is limited to students currently enrolled at National Tsing Hua University (NTHU) or those who are planning to enroll soon.
請以英文寄信，因為我不會中文。此機會僅限於目前就讀於國立清華大學的學生，或即將入學者。

♠️ What We Can Offer / 我們提供

• One-on-one mentorship by internationally experienced faculty
  由具有國際經驗的教師一對一指導（曾任教於清大、大阪大等）
• Research opportunities in cutting-edge topics: quantum information, holography (AdS/CFT), and the quantum theory of black holes
  涵蓋前沿研究主題：量子資訊、全像理論（AdS/CFT）、以及黑洞的量子理論
• Note: Co-authorship on academic papers requires meaningful contributions. Passive or symbolic participation is not sufficient. Thus, we welcome motivated students who are willing to participate in the research process actively.
  備註：我們歡迎有動機、願意積極參與研究的學生。共同作者需對研究有實質貢獻，僅象徵性參與無法列名。

♣️ Application Requirements 申請須知

• Please write to me by email：iizuka★phys.nthu.edu.tw [★=@]. After that, we will set up an interview. We will ask the following questions during the interview.
  請用英文寄送電子郵件給我：iizuka★phys.nthu.edu.tw [★ = @]。之後我們會安排面談，相關問題將於面談時直接詢問。
  

♦️ What We Will Ask in the Interview 面試時我們會問的問題

• Why you want to join my group? 你為什麼想加入我的研究團隊？
• Your favorite idea or concept in physics and why? 您最欣賞的物理概念是？ 為什麼？
• A research topic you would like to explore: 您想探索的研究主題是什麼？
• Your future academic or career goals 請談談您未來的學術或職涯目標。
• A few simple questions to assess your basic understanding of physics. 我們會問一些簡單的問題，以了解你對物理的基本理解。