ニュース
243件のニュース / 2021年
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2021-11-02
セミナーレポート
Report of iTHEMS colloquium - High-Energy Neutrino Astrophysics in the Multimessenger Era
Our Universe is filled with mysterious high-energy emissions: Cosmic-rays (CR), neutrinos, and gamma-ray photons. They could be generated at the same source populations although we have not yet confirmed. Among these messenger particles, the neutrino is a special one to probe their origins. Cosmic rays are deflected by the magnetic field, while high-energy photons are attenuated during its propagation. Only the neutrino could preserve the information about the production sites. Also, the neutrino should be a messenger to physics beyond the Standard Model. The fact that the neutrinos have finite masses itself requires the extension of the Standard Model. Its origin could be related to dark matter, new kinds of interactions, and so on. On-going and planned experiments should enable us to access these problems by combining spectrum, timing, and flavor information. In this colloquium, Prof. Kohta Murase reviewed the above contents focusing on the latest results from neutrino observations and the development of the source modeling in the multi-messenger approach. About 100 people have enjoyed his talk. Lots of questions and some deep discussions related to the topic continued after the main part of the talk. We would like to thank him again and express our great appreciation for your attendance. Reported by Nagisa Hiroshima
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2021-10-29
セミナーレポート
iTHEMS Biology Seminar by Prof. Ikkyu Aihara on October 28, 2021
In the Biology Seminar on 28th October, Ikkyu Aihara (University of Tsukuba) gave a talk on frog chorus and its synchronization phenomena using experimental, fieldwork, and mathematical models. An earthquake that had occurred just before the seminar made me a bit nervous about whether we can hold the seminar, but the talk thankfully went very well. As I'm a big fan of Kuramoto-model as well as Ikkyu's work, I really enjoyed the talk on the whole. I saw one of the most interesting experiments of his ongoing work, and so I'm really looking forward to seeing the work being published. I also enjoyed a private conversation between Ikkyu and Kazuyuki Aihara before and during the talk! Thank you again for the great talk, Ikkyu-san! Reported by Ryosuke Iritani
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2021-10-28
今週の論文Week 5, October 2021
Title: On an Average Goldbach Representation Formula of Fujii Author: D. A. Goldston, Ade Irma Suriajaya arXiv: http://arxiv.org/abs/2110.14250v1 Title: Negative string tension of higher-charge Schwinger model via digital quantum simulation Author: Masazumi Honda, Etsuko Itou, Yuta Kikuchi, Yuya Tanizaki arXiv: http://arxiv.org/abs/2110.14105v1 Title: A new perspective on cosmology through Supernovae Ia and Gamma Ray Bursts Author: Biagio De Simone, Via Nielson, Enrico Rinaldi, Maria Giovanna Dainotti arXiv: http://arxiv.org/abs/2110.11930v1 Title: QCD viscosity by combining the gradient flow and sparse modeling methods Author: Etsuko Itou, Yuki Nagai arXiv: http://arxiv.org/abs/2110.13417v1 Title: Optical spin transport theory of spin-1/2 topological Fermi superfluids Author: Hiroyuki Tajima, Yuta Sekino, Shun Uchino arXiv: http://arxiv.org/abs/2109.14505v2 Title: Unified Description of Tunneling Transport in Ultracold Atomic Gases Author: Hiroyuki Tajima, Daigo Oue, Mamoru Matsuo arXiv: http://arxiv.org/abs/2110.11701v1
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2021-10-28
イベントスケジュール
Events for the 1st week of November 2021
Tuesday, November 2, 13:30– 15:00 iTHEMS Theoretical Physics Seminar Thursday, November 4, 13:30– 15:00 Information Theory SG Seminar Friday, November 5, 12:30- Coffee Meeting
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2021-10-28
ホットトピック
森重文特別顧問が文化勲章に選出されました
この度、京都大学高等研究院院長で理研iTHEMSの特別顧問でもある森重文さんが、「数学、とりわけ代数幾何学の分野において、代数多様体の極小モデル理論である「森理論」を創造し、数理科学の広範な分野に大きな影響を与える顕著な業績を上げ、斯学の発展に多大な貢献をした」功績を認められ、文化勲章を授与されることになりました。森重文さんのご専門は数学、特に代数幾何学です。当該分野の中心的テーマである「代数多様体の分類問題」における大きな業績により1990年の国際数学者会議でフィールズ賞を受賞された後も、関連領域の研究を精力的に牽引し続けてこられました。 代数多様体とは、大雑把には、代数方程式の解集合として表される幾何学的な対象（の一般化）です。例えば、x2 + y2 = 1という代数方程式の（実数範囲での）零点集合は原点を中心とする単位円ですが、これは代数多様体の一種です。代数多様体を考えることで、代数に関する問題を幾何学の問題に変換することができます。 代数多様体の性質を調べることは代数幾何学の重要な使命ですが、一つ一つの代数多様体について逐一調べていてはきりがありません。そこで、よく似ている代数多様体は同じ「生物種」と見なして、それを「生物図鑑」のように分類しようというのが「代数多様体の分類問題」です。ここで「よく似ている」とは、「双有理変換」と呼ばれる操作によって互いに移りあうことを意味します。双有理変換とは、代数多様体の低次元の部分のみを変形する操作です。双有理変換を行っても、代数多様体のほとんどの部分は変わらないので、この操作でうつりあうものは自然に同じ種類と思うことができます。 では、そのような「生物種」の中で、一体どの「個体」を図鑑の中に代表例として載せるべきでしょうか？こういう時「可能な限りシンプルな代表例」を持ってきたいというのが数学者の考えることです。そのような「可能な限りシンプルな代表例」のことを代数多様体の「極小モデル」と呼びます。 例えば、１次元の代数多様体（曲線）は一般には特異点を持ちますが、双有理変換により、特異点のない曲線に変換できます（そして、同じ「生物種」の中に特異点のない曲線はただ１つしかありません）。これが曲線の場合の極小モデルです。２次元の代数多様体（曲面）も、やはり双有理変換により特異点のない滑らかな曲面に変換できますが、実はこの場合には、同じ「生物種」の中に、特異点のない曲面が無数に存在します。そこで、曲面の中に存在する「(-1)-曲線」と呼ばれる余分な膨らみを次々に潰していくと、それ以上は小さくできない滑らかな曲面に到達します。こうして得られた最も無駄のない曲面、すなわち極小モデルを、「生物種」の代表例とするわけです。 では、３次元以上の、高次元の代数多様体についてはどうでしょうか？この場合にも、双有理変換により特異点のない滑らかな代数多様体に変換できます（これは同じくフィールズ賞受賞者である広中平祐氏の重要な業績です）。しかし、３次元以上の場合には、代数多様体の中の余分な膨らみを潰していく過程で、どうしても特異点が出現してしまうケースを排除できないため、問題がより難しくなります。しかし森さんは「端末特異点」と呼ばれる緩やかな特異点のみを許せば、３次元の代数多様体の極小モデルを構成できることを証明しました。特異点の悪さを最小限に抑えつつ、余分な膨らみを潰し切ることは大変難しいのですが、森さんはそれを可能にする理論を構築したのです。森さんが２次元と３次元の間の分厚い壁を突破したことにより、現在では４次元以上の分類理論も大きく進展しています。また最近では、整数論などへの応用も広がりつつあり、これからもますます目が離せません。 森重文さんの偉大な業績のごく一部をご紹介させていただきました。 森さんの受賞と高次元極小モデル理論の進展をお慶び申し上げるとともに、森理論の更なる進展と数理科学振興へのますますのご活躍をiTHEMS一同祈念しております。 宮﨑弘安 (iTHEMSを代表して)
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2021-10-27
セミナーレポート
Quantum Matter SG seminar by Dr. Robert Peters on October 20, 2021
The Quantum Matter Study Group invited Dr. Robert Peters from Kyoto University to talk about nonlinear responses in strongly correlated systems. In the beginning, the speaker introduced nonlinear responses by reviewing several related experimental data, including a nonlinear photo-induced current. Then, going beyond linear response theory, he explained the approach to compute nonlinear responses in strongly correlated systems. Here, the essential step of his work was to neglect vertex corrections, which enables the analysis of higher-order correlation functions within established frameworks of, e.g., dynamical mean field theory. Equipped with this tool, he showed nonreciprocal conductivity in a ferromagnetic non-centrosymmetric heavy Fermion compound and giant nonlinear Hall effect in a Weyl-Kondo-Semimetal. Reported by Thore Posske (University of Hamburg, Germany) and Ching-Kai Chiu
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2021-10-27
セミナーレポート
DMWG Seminar by Prof. Takashi Toma on October 20, 2021
Among the varieties of dark matter (DM) candidates, the so-called WIMP (an abbreviation of the weakly interacting massive particle) is famous for its beautiful mechanism to achieve the current DM density. In the early Universe, WIMP was in the thermal bath of the Standard Model (SM) particles. In this stage, (i) DM+DM->SM+SM, (ii)SM+SM->DM+DM interaction as well as (iii)DM+SM-> DM+SM interaction occur frequently enough. The strategy searching for each process corresponds to indirect, collider, and direct detection experiments. The cross-section (i.e., the interaction rate) of the above processes correlates with each other. The dropping off of the interaction rate of the process (i) below to the Hubble expansion rate of the Universe fixes the number density of DM particles. We need only two parameters in this WIMP freeze-out scenario: mass and the interaction cross-section. Nowadays the constraints from direct detection experiments are so severe that WIMP in the low mass range of m
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2021-10-27
セミナーレポート
NEW WG Seminar by Mr. Akihiro Yamada on October 20, 2021
Akihiro Yamada (Keio U.) gaive a talk on "Floquet vacuum engineering: laser-driven chiral soliton lattice in the QCD vacuum" based on his recently published paper [1]. After briefly introducing the Floquet theory and the chiral perturbation theory, Akihiro showed emergence of chiral soliton lattice structure in the QCD vacuum under a very strong laser field with large frequency. About 20 people have joined the seminar, and we had fruitful discussions during and after the seminar. Reported by Hidetoshi Taya
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2021-10-27
セミナーレポート
iTHEMS Biology Seminar by Dr. Hiroshi Yokota on October 21, 2021
In the iTHEMS Biology seminar on October 21, I talked about the driving force and the mechanism of the chromosome formation. The chromosome is constructed by chromatin fiber condensed into the rod-like shape. The rod-like shape comes from the consecutive chromatin loops. The driving force of the chromosome formation is one of the controversial issues. Two hypotheses on the driving force are considered: energy gain from ATP hydrolysis and thermal fluctuation energy. In this talk, I discussed the driving force derived from the free energy of the chromatin loop. Moreover, the mechanism associated with each driving force was also discussed by using the dynamical model based on the free energy. The result implies that these mechanisms dynamically switch. This study is collaborated with Masashi Tachikawa in Kyoto University who is also visiting scientist in iTHEMS. As there were various questions and discussions from the audiences, I was so happy. Thank you very much!
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2021-10-25
ホットトピック
小谷元子客員主管研究員が国際学術会議の次期会長に選出されました
10月14日に開催された国際学術会議（ISC：International Science Council）総会で、小谷元子客員主管研究員が、国際学術会議の次期会長（President-elect）に選出されました。任期は2024年から3年間です。 詳細は、関連リンクをご覧ください。
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2021-10-21
今週の論文Week 4, October 2021
Title: Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay Author: He-Lei Liu, Zi-Gao Dai, Guo-Liang Lv, Akira Dohi, Gao-Chan Yong, Masa-aki Hashimoto arXiv: http://arxiv.org/abs/2110.09729v1 Title: Prospects of fast flavor neutrino conversion in rotating core-collapse supernovae Author: Akira Harada, Hiroki Nagakura arXiv: http://arxiv.org/abs/2110.08291v1 Title: Involutions, knots, and Floer K-theory Author: Hokuto Konno, Jin Miyazawa, Masaki Taniguchi arXiv: http://arxiv.org/abs/2110.09258v1
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2021-10-21
イベントスケジュール
Events for the 5th week of October 2021
Tuesday, October 26, 10:00- Conference: Can social issues be solved by mathematical science? -attempts and challenges Thursday, October 28, 15:00- iTHEMS Colloquium Friday, October 29, 12:30- Coffee Meeting
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2021-10-20
プレスリリース
熱帯雨林樹木“フタバガキ”の乾燥応答遺伝子の数が増加していた －ゲノム解読から気候変動対策へ－
横浜市立大学木原生物学研究所 清水健太郎 客員教授（チューリッヒ大学教授兼任）、マレーシア森林研究所 Kevin Kit Siong Ng 主任研究員、Soon Leong Lee 遺伝学グループ長、国際農林水産業研究センター 小林正樹 主任研究員、理化学研究所 数理創造プログラム ジェフリ・フォーセット 上級研究員、金沢大学 西山智明 助教、株式会社ヒューマノーム研究所 瀬々潤 代表取締役らの研究グループは、地球環境にとっても輸入木材としても重要な熱帯樹種フタバガキ科樹木のゲノムを解読しました。雨に恵まれた東アジア熱帯に生育しているにもかかわらず、予想外なことに乾燥応答遺伝子が増加しており、熱帯での稀な乾燥の重要性が明らかになりました。地球環境変動によって、熱帯ではエルニーニョ・南方振動と関連する大規模乾燥が深刻化しており、本研究の成果の持続的林業と熱帯雨林保全へ向けた応用が期待されます。 詳細は横浜市立大学のウェブサイトをご覧下さい。
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2021-10-19
セミナーレポート
Quantum Matter SG seminar by Mr. Seishiro Ono on October 12, 2021
Quantum Matter Study Group invited Seishiro Ono from the University of Tokyo to give a talk about symmetry indicators for topological (nodal) superconductors. First, he gave a review of symmetry indicators for topological insulators. In condensed matter physics, using topological invariants to search for topological materials is difficult; alternatively, symmetry indicators serve a simpler calculation to identify topological states of matter since this method considers the properties located at symmetry invariant momenta. After the introduction, the speaker extended the indicator approach to topological (nodal) superconductors. Although the different types of superconducting pairings lead to complications in the symmetry-based classification, the speaker showed that their work classifies all the (magnetic) space groups with possible superconducting pairings. Furthermore, he demonstrated their own database server listing all the classification of the topological superconductors by using the approach of symmetry indicators. The work serves as an important guide for hunting topological superconductors. Reported by Ching-Kai Chiu
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2021-10-18
セミナーレポート
ABBL/iTHEMS Astro Seminar by Dr. Nobuya Nishimura on October 15, 2021
At the seminar, there were lots of questions and answers for r-process nucleosynthesis and kilonova events. The speaker presented lots of his excellent works on them, and the audience enjoyed his presentation with curiosity. Reported by Shigehiro Nagataki
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2021-10-14
今週の論文Week 3, October 2021
Title: The genome of Shorea leprosula (Dipterocarpaceae) highlights the ecological relevance of drought in aseasonal tropical rainforests Author: Kevin Kit Siong Ng, Masaki J. Kobayashi, Jeffrey A. Fawcett, Masaomi Hatakeyama, Timothy Paape, Chin Hong Ng, Choon Cheng Ang, Lee Hong Tnah, Chai Ting Lee, Tomoaki Nishiyama, Jun Sese, Michael J. O’Brien, Dario Copetti, Mohd Noor Mat Isa, Robert Cyril Ong, Mahardika Putra, Iskandar Z. Siregar, Sapto Indrioko, Yoshiko Kosugi, Ayako Izuno, Yuji Isagi, Soon Leong Lee, Kentaro K. Shimizu Journal Reference: Commun Biol 4, 1166 (2021) doi: https://doi.org/10.1038/s42003-021-02682-1 Title: Effect of advancing age on the reproductive performance of Japanese Thoroughbred broodmares Author: Jeffrey A. FAWCETT, Hideki INNAN, Takeru TSUCHIYA, Fumio SATO Journal Reference: J. Equine Sci. Vol. 32, No. 2, pp. 31–37 (2021) doi: https://doi.org/10.1294/jes.32.31 Title: Universal relation for supernova gravitational waves Author: Hajime Sotani, Tomoya Takiwaki, Hajime Togashi arXiv: http://arxiv.org/abs/2110.03131v2 Title: Topology and symmetry of circular photogalvanic effect in the chiral multifold semimetals: a review Author: Congcong Le, Yan Sun doi: https://doi.org/10.1088/1361-648X/ac2928 arXiv: http://arxiv.org/abs/2110.03434v1
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2021-10-13
受賞情報
廣島渚客員研究員が富山大学学長賞 第5回「未知に挑む女性研究者賞」を受賞
富山大学が、富山大学学長賞 第5回「未知に挑む女性研究者賞」の受賞者を発表し、廣島渚客員研究員が女性研究者部門で受賞しました。詳細は富山大学のウェブサイトをご覧下さい。
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2021-10-13
今週の注目人物
Self-introduction: Gilberto Nakamura
My name is Gilberto Nakamura and I joined iTHEMS as a postdoctoral researcher in Oct 2021, after working as a postdoctoral fellow at IJCLab/CNRS in France. I'm interested on the role of noise and correlations in biologically inspired systems. The relation between fluctuations and correlations lies at the heart of the theory of critical phenomena, with ramifications in Statistical Physics and Quantum Field Theory. Fluctuations in biological systems are further exacerbated by the innate variability of organisms, adding richness to the dynamics and promoting the emergence of complex behavior. More recently, I have worked on disease-spreading dynamics, viral infections, and migration of cancer cells, all of which have a significant impact on human health and require continued interdisciplinary efforts across Mathematics, Physics, and Biology. My current focus has been on bottom-up approaches, starting from microscopic stochastic models and working them out into the hydrodynamic limit, with support from numerical Monte Carlo simulations, followed by parameter extraction from data. I am sure the interdisciplinary environment fostered by iTHEMS will promote new collaborations and further advance my research goals.
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2021-10-12
セミナーレポート
Quantum Matter SG seminar by Prof. Bohm-Jung Yang on October 7, 2021
The Quantum Matter study group had the honor to invite Prof. Bohm-Jung Yang to give a talk on October 7th. He talked about wave function geometry and anomalous Landau levels of flat bands. He started with a heuristic introduction by explaining the geometry matters in a flat band, including the notion of the (Hilbert-Schmidt) quantum distance and the quantum metric. Particularly, he used a Kagome lattice as an example of the singular touching point of the flat band and quadratic band locked by the geometry. Furthermore, in the presence of a magnetic field, the singular flat band evolves into very dense anomalous Landau levels. Remarkably, the relation between the Landau level spreading and the maximum of the quantum distance can be described by a universal formula, independent of material parameters. In consequence, deducing the Landau level spreading in (spectroscopic) experiments would allow for the measurement of the quantum distance, thus probing the quantum geometry of the wave functions. The study was extended to the (spin-orbit-coupled) Lieb lattice with one flat band sandwiched by two dispersive bands. In this case, the Landau level spreading of the isolated flat band is determined by the fidelity tensor. This talk showed us the interesting and subtle interplay between the band flatness and the Landau levels. Reported by Ching-Kai Chiu and Chen-Hsuan Hsu (CEMS, RIKEN)
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2021-10-11
セミナーレポート
iTHEMS Theoretical Physics Seminar by Prof. Keisuke Izumi on September 13, 2021
At the seminar organized by the iTHEMS-physics study group, Prof. Keisuke Izumi discussed the S-matrix unitarity toward UV completion. Einstein gravity is not renormalizable and does not hold perturbative unitarity at high energy. This is the main reason why the construction of quantum gravity is difficult. A conjecture was proposed by Llewellyn Smith, "renormalizablility and tree-unitarity at high energy give the same conditions". This conjecture would be important because it shows that, if a theory is constructed such that unitarity is satisfied, renormalizablility holds automatically, and vice versa. Unfortunately, a counterexample was pointed out. If a theory involves higher derivatives, there exists a theory which is renormalizable but does not satisfy tree-unitarity. A candidate of quantum gravity, the quadratic gravity (R_{\mu\nu}^2 gravity), is one of the examples. Therefore, Llewellyn Smith's conjecture would not be useful for the discussion of quantum gravity. Then, Prof. Izumi and his collaborators introduced a new conjecture, "renormalizablility and S-matrix unitarity (or often called pseudo-unitarity) at high energy give the same conditions". In his talk, Prof. Izumi explained Llewellyn Smith's conjecture and his contribution to it. Then, he introduced his new conjecture. Finally, he showed that his conjecture works well even in theories with higher derivatives. Reported by Ryo Namba
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2021-10-07
今週の論文Week 2, October 2021
Title: Confinement/deconfinement transition in the D0-brane matrix model -- A signature of M-theory? Author: Georg Bergner, Norbert Bodendorfer, Masanori Hanada, Stratos Pateloudis, Enrico Rinaldi, Andreas Schäfer, Pavlos Vranas, Hiromasa Watanabe arXiv: http://arxiv.org/abs/2110.01312v1 Title: Searching for TeV gamma-ray emission from SGR\,1935+2154 during its 2020 X-ray and radio bursting phase Author: H.E.S.S. Collaboration (Naomi Tsuji) Journal Reference: ApJ 919, 106-114 (2021) doi: https://doi.org/10.3847/1538-4357/ac0fe1 arXiv: http://arxiv.org/abs/2110.00636v1 Title: Heavy-quark spin polarization induced by Kondo effect under magnetic field Author: Daiki Suenaga, Yasufumi Araki, Kei Suzuki, Shigehiro Yasui arXiv: http://arxiv.org/abs/2109.14799v1 Title: Yu-Shiba-Rusinov states in a superconductor with topological Z2 bands Author: Ching-Kai Chiu, Ziqiang Wang arXiv: http://arxiv.org/abs/2109.15227v1 Title: Design strong anomalous Hall effect via spin canting in antiferromagnetic nodal line materials Author: Congcong Le, Claudia Felser, Yan Sun Journal Reference: PhysRevB.104.125145(2021) doi: https://doi.org/10.1103/PhysRevB.104.125145 arXiv: http://arxiv.org/abs/2105.09237v1
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2021-10-07
イベントスケジュール
Events for the 3rd week of October 2021
Tuesday, October 12, 16:00- Quantum Matter Seminar Friday, October 15, 12:30- Coffee Meeting
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2021-10-04
今週の注目人物
Self-introduction: Yixin Guo
My name is Yixin GUO, a Junior Research Associate joined in iTHEMS from October 2021. I come from China, and now study in the Doctoral Course at The University of Tokyo. I am majoring in theoretical nuclear physics. I am mainly interested in (but not only) the quantum many-body problem, nuclear structure theory, density functional theory, and nuclear reaction theory. I also have some experience in the accelerator physics. I look forward to exchanging ideas with various researchers from different fields.
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2021-09-30
今週の論文Week 5, September 2021
Title: Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes Author: C. B. Adams, et al. (N. Tsuji) arXiv: http://arxiv.org/abs/2109.11894v1 Title: Design strong anomalous Hall effect via spin canting in antiferromagnetic nodal line materials Author: Congcong Le, Claudia Felser, Yan Sun Journal Reference: PhysRevB.104.125145(2021) doi: https://doi.org/10.1103/PhysRevB.104.125145 arXiv: http://arxiv.org/abs/2105.09237v1
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2021-09-29
セミナーレポート
Report of iTHEMS colloquium - Finding Gravitational Waves from the Early Universe
Prof. Eiichiro Komatsu, a director at the Max Planck Institute for Astrophysics (Germany), shared his enthusiasm for observational aspects of cosmology and in particular the primordial gravitational waves (GWs) generated during the earliest stage of our Universe, called cosmic inflation. Such GWs distort the space while propagating and leave footprints as the polarizations of the cosmic microwave background (CMB) and as a more direct signal at the GW interferometers. As a world-leading expert on all areas of cosmology, Prof. Komatsu explained the fundamental aspects of CMB and GW observations and their implications in understanding the physics of the primordial Universe (from his remark, "We all came from quantum fluctuations"). He made his talk visually accessible to non-experts while providing fresh interpretations of the data in cosmological observations. He also clarified the importance and excitement of the upcoming LiteBIRD project, the first CMB mission led by Japan, which expects its launch toward the end of 2020's. After the official part of his talk, he remained to be available for both scientific and non-scientific discussions with the audience in an informal setting and exchanged more technically involved thoughts as well as his everyday-life experiences. Reported by Ryo Namba
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2021-09-23
イベントスケジュール
Events for the 5th week of September 2021
Monday, September 27, 16:00- iTHEMS Colloquium Friday, October 1, 12:30- Coffee Meeting
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2021-09-23
今週の論文Week 4, September 2021
Title: On the ease of excitation of black hole ringing: Quantifying the importance of overtones by the excitation factors Author: Naritaka Oshita arXiv: http://arxiv.org/abs/2109.09757v1 Title: Effective field theory of fluctuating wall in open systems: from a kink in Josephson junction to general domain wall Author: Keisuke Fujii, Masaru Hongo arXiv: http://arxiv.org/abs/2109.10335v1 Title: Persistence of cluster structure in the ground state of $^{11}$B Author: Naoyuki Itagaki, Tomoya Naito, Yuichi Hirata arXiv: http://arxiv.org/abs/2109.09957v1 Title: High-dimensional structure learning of sparse vector autoregressive models using fractional marginal pseudo-likelihood Author: Kimmo Suotsalo, Yingying Xu, Jukka Corander, Johan Pensar Journal Reference: Stat Comput 31, 73 (2021) doi: https://doi.org/10.1007/s11222-021-10049-z arXiv: http://arxiv.org/abs/2011.01484v1 Title: Principal-Axis Analysis of the Eddington Tensor for the Early Post-Bounce Phase of Rotational Core-Collapse Supernovae Author: Wakana Iwakami, Akira Harada, Hiroki Nagakura, Ryuichiro Akaho, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada arXiv: http://arxiv.org/abs/2109.05846v2 Title: Universal relations between the quasinormal modes of neutron star and tidal deformability Author: Hajime Sotani, Bharat Kumar arXiv: http://arxiv.org/abs/2109.08145v1 Title: A semi-analytic afterglow with thermal electrons and synchrotron self-Compton emission Author: Donald C. Warren, Maria Dainotti, Maxim V. Barkov, Bjorn Ahlgren, Hirotaka Ito, Shigehiro Nagataki arXiv: http://arxiv.org/abs/2109.07687v1 Title: Derivative expansion in the HAL QCD method for a separable potential Author: Sinya Aoki, Koichi Yazaki arXiv: http://arxiv.org/abs/2109.07665v1
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2021-09-22
ホットトピック
数学と物理 ―トポロジーと絶縁体と私の研究生活
小澤知己客員研究員が「数理女子」サイトでトポロジカル絶縁体や研究生活、日常生活などについて執筆しています。記事は関連リンクからご覧ください。
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2021-09-17
セミナーレポート
NEW WG Seminar by Prof. Yuta Murakami on September 15, 2021
Yuta Murakami from Tokyo Institute of Technology told us about "High-harmonic generation in strongly correlated systems." High-harmonic generation (HHG) by strong AC electric fields is one of the hottest topics in cond-mat physics. After a brief overview of HHG in various materials such as gasses and semi-conductors and also recent experimental results in Mott insulators, Yuta explained his recent numerical studies on HHG in strongly correlated systems and clarified unique features of HHG arising from the strongly-correlated nature. About 30 people joined the seminar and we enjoyed fruitful discussions during and after the seminar. Reported by Hidetoshi Taya
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2021-09-17
セミナーレポート
NEW WG Seminar by Prof. Matteo Baggioli on September 10, 2021
Matteo Baggioli (Jiao-Tong U. Shanghai) gave a talk on "Towards a description of amorphous solids and viscoelastic materials using effective field theory and holographic methods." Amorphous and viscoelastic materials appear in many places, not only in scientific problems but also in our daily life. Despite its ubiquity, there are many intriguing phenomena that are not yet understood, in particular, in the non-linear regime. In the talk, Matteo explained his recent attempts to formulate non-linear responses in amorphous and viscoelastic materials based on holographic and effective-field-theory techniques. Matteo also discussed open problems and future directions that we can pursue in the future. There were about 30 participants from various fields of physics, and we had fruitful discussions from a broad point of view during and even after the talk. Reported by Hidetoshi Taya
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2021-09-17
プレスリリース
植物の多種共存を説明する新たなメカニズムの発見 －開花前の自家受粉の進化が引き起こす進化的救助－
岡山大学学術研究院環境生命科学学域（工）の勝原光希助教（当時所属：神戸大学大学院人間発達環境学研究科）、東京都立大学大学院理学研究科の立木佑弥助教、理化学研究所数理創造プログラムの入谷亮介研究員（当時所属：University of California Berkeley, University of Exeter）、神戸大学大学院人間発達環境学研究科の丑丸敦史教授は、個体ベースモデルを用いたシミュレーションを行い、同じ種の送粉者を共有し競争関係にある植物2種において、個体数の少ない種でより高い自家受粉率が進化することで個体数が増加に転じる進化的救助が発生し、それによって2種の長期的な共存が促進されることを明らかにしました。 本結果は、複数の植物種が同所的に開花して共存できる理由にまったく新しい理論を加えると共に、植物で多様な繁殖戦略が進化してきた要因についても新たな視点を与えるものです。陸上生態系の根幹を支える植物の多様性の創出・維持メカニズムを理解することは、生物多様性の源泉の理解のみならず、生態系と調和した持続可能な社会形成を考える上でも不可欠であり、基礎・応用の両面において重要な知見であるといえます。 詳細は関連リンクから岡山大学のプレスリリースをご覧ください。
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2021-09-16
今週の論文Week 3, September 2021
Title: Equation of state of neutron star matter and its warm extension with an interacting hadron resonance gas Author: Yuki Fujimoto, Kenji Fukushima, Yoshimasa Hidaka, Atsuki Hiraguchi, Kei Iida arXiv: http://arxiv.org/abs/2109.06799v1
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2021-09-09
イベントスケジュール
Events for the 3rd week of September 2021
Monday, September 13, 13:30- iTHEMS Theoretical Physics Seminar Tuesday, September 14, 9:30- DMWG Seminar Wednesday, September 15, 13:30- NEW WG Seminar Friday, September 17, 12:30- Coffee Meeting
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2021-09-09
今週の論文Week 2, September 2021
Title: Subregion Spectrum Form Factor via Pseudo Entropy Author: Kanato Goto, Masahiro Nozaki, Kotaro Tamaoka arXiv: http://arxiv.org/abs/2109.00372v1
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2021-09-09
セミナーレポート
iTHEMS Biology Seminar by Dr. Euki Yazaki on September 9, 2021
Molecular phylogenetic analysis is one of the most important analysis methods in biology. If used well, it can help us understand how organisms diversified and how genes evolved. The methods of molecular phylogenetic analysis are subject to debate, so we are familiar with the mathematical background. However, we are not so familiar with how the data sets for phylogenetic analysis are made up. In this Biology Seminar, the main alignment algorithms for making data sets were explained and discussed. Scoring is important in alignment algorithms, and there was a discussion on scoring for amino acid and nucleic acid mutations and scoring for gap penalties. The discussion on alignment distance was also heated. I hope the audience all enjoyed it. I would like to have another discussion on phylogenetic analysis and mathematical background next time. Thank you very much!
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2021-09-09
セミナーレポート
ABBL-iTHEMS Joint Seminar by Dr. Yosuke Mizuno on September 3, 2021
Prof. Yosuke Mizuno (Tsung-Dao Lee Institute, Shanghai JiaoTong University) gave an excellent talk on "The Polarised ring ofthe Supermassive Black Hole in M87: EHT observations andtheoretical modeling". He introduced that the Event HorizonTelescope (EHT) had mapped the central compact radio source of theelliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Recently EHT provided new images of the polarised emissionaround the central black hole in M87 on event-horizon scale. Thispolarised synchrotron emission probes the structure of magnetic fieldsand the plasma properties near the black hole. He and hiscollaborators found that the net azimuthal linear polarisationpattern may result from organised, poloidal magnetic fields in the emission region. In a quantitative comparison with a large simulated polarimetric image library, he found that magnetically arrested accretion disks are favoured to explain polarimetric EHT observations. In this talk, he also discussed about a new modelling study of M87jets in the collimation and acceleration region. Reported by Shigehiro Nagataki
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2021-09-08
今週の注目人物
Self-introduction: Matthias Berwein
My name is Matthias Berwein and I'm from Germany. I did my undergraduate studies in physics at TU Munich from 2006 to 2011, followed by a PhD 2012-2016 also at TU Munich in the group of Nora Brambilla. Then I came to Japan for my first postdoc at Tohoku University in Sendai under a JSPS fellowship with Yukinari Sumino. Since 2018 I've been at RIKEN, first in the SPDR program at Quantum Hadron Physics Lab, and from 2021 in iTHEMS. The focus of my research lies in theoretical studies of the strong interactions through the theory of quantum chromodynamics and with a special emphasis on heavy quarks. I have worked on several projects on the static quark potential, heavy quarkonium hybrids, and heavy quarks at finite temperature, using perturbative calculations and effective theory methods. Currently, I'm studying properties of the energy-momentum tensor in these environments. I look forward to many fruitful interactions with fellow researchers here at iTHEMS.
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2021-09-03
セミナーレポート
Quantum Matter SG seminar by Dr. Levente Rózsa on September 1, 2021
Dr. Levente Rózsa gave a talk about Yu-Shiba-Rusinov (YSR) states and other localized states appearing in superconductors for Quantum Matter Study Group on September 1st, 2021. There are three distinct types of localized in-gap states in superconductors —- Majorana bound states, YSR states, and Caroli-de Genne-Matricon states. Dr. Rózsa first introduced Majorana bound states emerging in topological superconductors. Next, he talked about the anisotropic spacial distribution of the YSR states on the La surface (0001). The YSR state is a localized in-gap state induced by magnetic impurity in a superconductor. He showed that this anisotropy stems from the anisotropic Fermi surface. Furthermore, he discussed the localized states appearing in vortex cores are Caroli-de Genne-Matricon states, instead of Majorana bound states. He went through the experimental details and compared them with his theoretical simulation. The talk was well-organized and clear. We thank Dr. Rózsa for sharing his interesting research works. Reported by Thore Posske (University of Hamburg, Germany) and Ching-Kai Chiu
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2021-09-03
セミナーレポート
iTHEMS Biology Seminar by Dr. Yingying Xu on September 2, 2021
In today's Biology Seminar, Yingying Xu (iTHEMS) introduced one paper arguing the quantitative explanation for immune-escape of virus by means of quasispecies dynamics models with Gillespie algorithm. She firstly explained the background information about the immune systems. She then taught us how the authors simulated the dynamics and made a comparison with experimental data. We finally discussed potential future directions to further development of quantitative modeling of chronic or acute infectious virus, highlighting a potential issue in estimating the mutation rate of virus. We learned a lot from this journal club, thank you so much for the great talk, Yingying! Reported by Ryosuke Iritani
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2021-09-02
今週の論文Week 1, September 2021
Title: Anomaly-induced edge currents in hydrodynamics with parity anomaly Author: Takuya Furusawa, Masaru Hongo arXiv: http://arxiv.org/abs/2108.12192v1 Title: Near-threshold Spectrum from Uniformized Mittag-Leffler Expansion -Pole Structure of $Z(3900)$- Author: Wren A. Yamada, Osamu Morimatsu, Toru Sato, Koichi Yazaki arXiv: http://arxiv.org/abs/2108.11605v1 Title: Subregion Spectrum Form Factor via Pseudo Entropy Author: Kanato Goto, Masahiro Nozaki, Kotaro Tamaoka arXiv: http://arxiv.org/abs/2109.00372v1
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2021-09-02
イベントスケジュール
Events for the 2nd week of September 2021
Friday, September 10, 12:30- Coffee Meeting Friday, September 10, 13:30- NEW WG Seminar
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2021-08-31
プレスリリース
スパコンで予言する魅惑の新粒子「チャームダイオメガ」 －クォーク6個状態の謎の解明に新たな1ページが加わる－
理化学研究所（理研）数理創造プログラムの杉浦拓也特別研究員、初田哲男プログラムディレクター、土井琢身専任研究員含む研究グループは、チャームクォーク6個からなる新粒子「チャームダイオメガ（ΩcccΩccc）」の存在を理論的に予言しました。 続きは、関連リンクをご覧ください。
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2021-08-30
セミナーレポート
iTHEMS Biology Seminar by Dr. Gen Kurosawa on August 26, 2021
During this covid-19 crisis, we check our body temperature (Tb) every day since Tb is essential variable of our body. In fact, some organisms like humans try to keep Tb constant, but some other organisms chose completely different strategies, including hibernation (冬眠). On August 26, I talked about hibernation at the iTHEMS Biology Seminar. Hibernation is a strategy for the organisms, including a primate to survive in a severe season with limited food and water availability. Although there have been a lot of studies about hibernation since the era of Aristotle, fundamental problems of hibernation remain unknown. Recently, we started to investigate mathematically body temperature profile of hibernating hamsters. During hibernation, the organisms drastically decrease their basal metabolisms, drop their body temperature (Tb) more than 10 degree, and become immobile. Mysteriously, Tb during hibernation does not remain constant at very low value, but greatly fluctuates with inconstant period of several days. At the seminar, I showed that a simple model can reproduce well and forecast Tb data during hibernation. Thankfully, there were a lot of questions and suggestions about the method of time-series analysis, hibernating species, and so on which are precious to me. This study is the collaboration with Prof. Yoshifumi Yamaguchi at Institute of Low Temperature Science, Hokkaido Univ and Shingo Gibo at iTHEMS. I’m really enjoying this research. I am happy if the audiences enjoyed the seminar and forgot about the heat. Thanks!
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2021-08-27
ホットトピック
RIKEN-Vancouver Joint Workshop on Quantum Computing was held on August 24-25, 2021
RIKEN-Vancouver Joint Workshop on Quantum Computing was held online on August 24-25. The main aim of this workshop is that the quantum people in RIKEN (iTHEMS and RQC) and Vancouver (Quantum BC) get together online to discuss scientific activities and explore future collaborations. There were altogether 164 registrations (90 from Japan, 62 from Canada and 12 from other countries). 12 scientific talks were presented together with 3 introduction to iTHEMS, RQC and Quantum BC. From iTHEMS, Jason Chang, Etsuko Itou, and Takumi Doi gave talks respectively on the Schroedinger equation, the U(1) gauge theory and combinatorial optimization. After each session, there were one-hour breakout sessions, so that people can ask further questions to the speakers, which worked very well. The workshop was an excellent first step toward a close tie between RIKEN quantum activities and Vancouver quantum activities.
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2021-08-26
今週の論文Week 5, August 2021
Title: Intraspecific Adaptation Load: A Mechanism for Species Coexistence Author: Masato Yamamichi, Daisuke Kyogoku, Ryosuke Iritani, Kazuya Kobayashi, Yuma Takahashi, Kaori Tsurui-Sato, Akira Yamawo, Shigeto Dobata, Kazuki Tsuji, Michio Kondoh Journal Reference: Trends in Ecology & Evolution 35(10), 897-907 (2020) doi: https://doi.org/10.1016/j.tree.2020.05.011 Title: Reproductive interference hampers species coexistence despite conspecific sperm precedence Author: Ryosuke Iritani, Suzuki Noriyuki Journal Reference: Ecology and Evolution 11(5),1957-1969 (2021) doi: https://doi.org/10.1002/ece3.7166 Title: Temporal changes in spatial variation: partitioning the extinction and colonisation components of beta diversity Author: Shinichi Tatsumi, Ryosuke Iritani, Marc W. Cadotte Journal Reference: Ecology Letters 24(5), 1063-1072 (2021) doi: https://doi.org/10.1111/ele.13720 Title: A solution to a sex ratio puzzle in Melittobia wasps Author: Jun Abe, Ryosuke Iritani, Koji Tsuchida, Yoshitaka Kamimura, Stuart A. West Journal Reference: PNAS 118 (20) e2024656118 (2021) doi: https://doi.org/10.1073/pnas.2024656118 Title: Cooperative interactions among females can lead to even more extraordinary sex ratios Author: Ryosuke Iritani, Stuart A. West, Jun Abe Journal Reference: Evolution Letters 5(4),370-384 (2021) doi: https://doi.org/10.1002/evl3.217 Title: Construction of energy density functional for arbitrary spin polarization using functional renormalization group Author: Takeru Yokota, Tomoya Naito arXiv: http://arxiv.org/abs/2108.10787v1 Title: Femtoscopic study of coupled-channel $NΞ$ and $ΛΛ$ interactions Author: Y. Kamiya, K. Sasaki, T. Fukui, T. Hyodo, K. Morita, K. Ogata, A. Ohnishi, T. Hatsuda arXiv: http://arxiv.org/abs/2108.09644v1 Title: Product of Random States and Spatial (Half-)Wormholes Author: Kanato Goto, Yuya Kusuki, Kotaro Tamaoka, Tomonori Ugajin arXiv: http://arxiv.org/abs/2108.08308v1 Title: Band width and the Rosenberg index Author: Yosuke Kubota arXiv: http://arxiv.org/abs/2108.08506v1
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2021-08-25
セミナーレポート
iTHEMS Biology Seminar by Dr. Naohiro Kawamoto on August 19, 2021
In iTHEMS Biology Seminar on August 19th, Dr. Naohiro Kawamoto (Osaka University) gave a talk on cyanobacterial circadian oscillations. It is known that three proteins (KaiA, KaiB and KaiC) are sufficient for generating self-sustained circadian oscillations in cyanobacterium. In this talk, Dr. Kawamoto experimentally showed that the lack of kaiA causes damped oscillation. Then, he analyzed the benefit of the damped circadian oscillation by using a simple mathematical model of the interaction between the damped and self-sustained oscillators. This analysis revealed that kaiA-less damped oscillator can resonate to another oscillatory process. Finally, he talked about evolution of related to evolution of circadian clock system for future work. After the talk, we enjoyed discussion about mathematical modeling of various types of coupled oscillators. Thank you very much, Naohiro! Reported by Shingo Gibo
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2021-08-25
セミナーレポート
Quantum Matter SG seminar by Prof. Daw-Wei Wang on August 23, 2021
On August 23rd, 2021, Quantum Matter Study Group invited Prof. Daw-Wei Wang to give a talk on the application of machine learning in condensed matter physics. First, he briefly introduced learning and emphasized using supervised machine learning in condensed matter physics. The practical condensed matter problem he focused on is the physics of many-body systems since the many-body problem is challenging to solve. By randomly choosing small portions of a many-body Hamiltonian, machine learning can almost accurately predict the energy of the many-body system. Prof. Wang used the 1D Fermi-Hubbard model and the 1D Ising model to show the consistency between the learning prediction and the known solutions. The limitation of this approach is that the system size has to be fixed. To resolve this problem, he used the transfer learning approach to extend the prediction to a larger system size by learning from small systems. In the end, he talked about identifying the topological phase transition points by improving the machine learning approach in the literature. The talk is very comprehensive and informative. We thank Prof. Wang for giving a wonderful talk. Reported by Ching-Kai Chiu
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2021-08-23
ホットトピック
日本経済新聞朝刊: 量子の威力、併用で生かす
入江 広隆 客員研究員（企業）のインタビュー記事が日本経済新聞のテクノロジストの時代に掲載されました。 従来のコンピューターと量子コンピューターの良いところを組み合わせた「ハイブリッド型」について答えています。 詳細は関連リンクをご覧下さい。
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2021-08-19
イベントスケジュール
Events for the 4th week of August 2021
Monday, August 23, 16:00- Quantum Matter Seminar Tuesday, August 24-25, RIKEN-Vancouver Joint Workshop on Quantum Computing Friday, August 27, 12:30- Coffee Meeting
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2021-08-19
今週の論文Week 4, August 2021
Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande: II. Impact of the Nuclear Equation of State Author: Ken'ichiro Nakazato, Fumi Nakanishi, Masayuki Harada, Yusuke Koshio, Yudai Suwa, Kohsuke Sumiyoshi, Akira Harada, Masamitsu Mori, Roger A. Wendell arXiv: http://arxiv.org/abs/2108.03009v1 Title: The generalized Nielsen-Ninomiya Theorem for the 17 wallpaper: Classification of 2D nodal superconductors, Dirac semimetals, and non-Hermitian nodal systems Author: Congcong Le, Zhesen Yang, Fan Cui, A. P. Schnyder, Ching-Kai Chiu arXiv: http://arxiv.org/abs/2108.04534v1 Title: Matrix Model simulations using Quantum Computing, Deep Learning, and Lattice Monte Carlo Author: Enrico Rinaldi, Xizhi Han, Mohammad Hassan, Yuan Feng, Franco Nori, Michael McGuigan, Masanori Hanada arXiv: http://arxiv.org/abs/2108.02942v1 Title: Universality of Interior Metric of Typical Black Holes Author: Hikaru Kawai, Yuki Yokokura arXiv: http://arxiv.org/abs/2108.02242v2 Title: Stability of the protoneutron stars toward black hole formation Author: Hajime Sotani, Kohsuke Sumiyoshi arXiv: http://arxiv.org/abs/2108.02484v1
243件のニュース / 2021年