News
217 news in 2022
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2022-09-15
Paper of the WeekWeek 3, September 2022
Title: Probing ΞN interaction through inversion of spin-doublets in ΞN αα nuclei Author: E. Hiyama, M. Isaka, T. Doi, T. Hatsuda arXiv: http://arxiv.org/abs/2209.06711v1 Title: dS{}_4 universe emergent from Kerr-AdS{}_5 spacetime: bubble nucleation catalyzed by a black hole Author: Issei Koga, Naritaka Oshita, Kazushige Ueda arXiv: http://arxiv.org/abs/2209.05625v1 Title: Spontaneous mass generation and chiral symmetry breaking in a lattice Nambu-Jona-Lasino model Author: Yukimi Goto, Tohru Koma arXiv: http://arxiv.org/abs/2209.06031v1 Title: Instantons, special cycles, and knot concordance Author: Aliakbar Daemi, Hayato Imori, Kouki Sato, Christopher Scaduto, Masaki Taniguchi arXiv: http://arxiv.org/abs/2209.05400v1 Title: Effects of finite sizes of atomic nuclei on shear modulus and torsional oscillations in neutron stars Author: Hajime Sotani, Hajime Togashi, Masatoshi Takano arXiv: http://arxiv.org/abs/2209.05416v1
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2022-09-08
Paper of the WeekWeek 2, September 2022
Title: Comparative Study on Charge Radii and Their Kinks at Magic Numbers Author: Tomoya Naito, Tomohiro Oishi, Hiroyuki Sagawa, Zhiheng Wang arXiv: http://arxiv.org/abs/2209.02857v1 Title: Establishment of an allotetraploid fern species, Lepisorus yamaokae Seriz., between two highly niche-differentiated parental species Author: Tao Fujiwara, Tsubasa Egashira, José Said Gutiérrez-Ortega, Kiyotaka Hori, Atsushi Ebihara, Yasuyuki Watano Journal Reference: American Journal of Botany doi: https://doi.org/10.1002/ajb2.16043 Title: Linear confinement in the partially-deconfined phase Author: Vaibhav Gautam, Masanori Hanada, Jack Holden, Enrico Rinaldi arXiv: http://arxiv.org/abs/2208.14402v1
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2022-09-06
Award
Dr. Tomoya Naito received 2022 RIBF Users Group Thesis Award
It is our greatest pleasure to inform you that our iTHEMS colleague, Tomoya Naito, received the "2022 RIBF Users Group Thesis Award". The awards honor the achievement of young scholars who earned the doctoral degree based on an RIBF experiment (using BigRIPS, GARIS, CRIB, RIPS, etc.), or a theoretical study related to physics at RIBF. The prize ceremony will be held on Sept. 20, 2022 at the annual RIBF Users Meeting.
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2022-09-06
Award
Dr. Michiya Mori received 2022 Takebe Katahiro Prize for Encouragement of Young Researchers
It is our greatest pleasure to inform you that our iTHEMS colleague, Michiya Mori, received 2022 Takebe Katahiro Prize for Encouragement of Young Researchers from The Mathematical Society of Japan (MSJ) for his contribution to the "Studies on preserver problems on operator algebras”. This prize was established by MSJ in honor of the renowned Japanese Mathematician in Edo period, Katahiro Takeba (1664 –1739).
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2022-09-06
Award
Dr. Shou Yoshikawa received 2022 Takebe Katahiro Prize for Encouragement of Young Researchers
It is our greatest pleasure to inform you that our iTHEMS colleague, Shou Yoshikawa, received 2022 Takebe Katahiro Prize for Encouragement of Young Researchers from The Mathematical Society of Japan (MSJ) for his contribution to the "Studies on algebraic varieties admitting a polarized endomorphism and the minimal model theory in mixed characteristic”. This prize was established by MSJ in honor of the renowned Japanese Mathematician in Edo period, Katahiro Takeba (1664 –1739).
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2022-09-05
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Tomohiko Oka on September 2, 2022
Supernova remnants (SNRs) are believed to be the site of cosmic ray acceleration up to PeV (called PeVatron), but there is no conclusive observational evidence. The possible reason is that only young SNRs (t_age < 1 kyr) can accelerate CRs up to PeV, and then the particles escape at the early stage, thus, the opportunity to observe them is limited. To investigate this scenario, Oka-san and his collaborators observed and analyzed the following two SNRs. First, they focused on SNR G106.3+2.7, the most promising SNR as a PeVatron, since 100 TeV gamma rays have been detected with air shower experiments. With the gamma-ray observation results, they discussed the origin of the PeV CR in the vicinity of this middle-aged SNR (t_age = 5-10 kyr) and then obtained the following interpretation: CRs accelerated at the SNR in the past are illuminating the molecular cloud and producing gamma rays at present. Second, they analyzed the observation data around SNR HB9 and newly found gamma-ray emissions outside the SNR shell at the molecular cloud region. The gamma-ray emission can be explained by the protons accelerated and escaped from the SNR in the past. Therefore, they have attempted to measure the time evolution of the maximum acceleration energy at the SNR by comparing the gamma-ray spectra at the SNR shell and cloud regions. In this seminar, Oka-san reported the analysis results of those two SNRs. Following the seminar talk, we discussed about the SNRs and high-energy gamma-rays from them. Reported by Shigehiro Nagataki
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2022-09-05
Award
Dr. Taketo Sano received the "academist Prize 2022"
On Aug.31, 2022, Taketo Sano (iTHEMS) received the "academist Prize 2022" at the event "academist Prize 2022 FINAL" where young researchers gather to discuss the future 30 years from now. Congratulations, Taketo!
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2022-09-05
Seminar Report
iTHEMS-RNC Meson Science Lab. Joint Seminar by Dr. Natsuki Tomida on August 26, 2022
Natsuki Tomida (SACRA, Kyoto Univ.) gave a hybrid talk on her experimental research on the bound eta'-meson in nuclei. This is related to the topic "Mesons in Nuclei" which is one of the central subjects in modern hadron physics. Both experimentalists and theorists from Nishina Center and iTHEMS joined the seminar, and there was a hot discussion on this interesting topic. Natsuki joined iTHEMS on Aug.1, 2022 as a visiting scientist to promote collaboration between SACRA's MACS program at Kyoto Univ. and RIKEN iTHEMS. On Sept. 20-21, 2022, she will visit iTHEMS again together with 11 undergraduate and graduate students of Kyoto University. Reported by Tetsuo Hatsuda
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2022-09-02
Seminar Report
iTHEMS Biology Seminar by Dr. Hiroshi Yokota on September 1, 2022
In the iTHEMS biology seminar on September 1st, I, Hiroshi Yokota, talked about a theoretical model of chromosome condensation based on Langevin simulation. In this model, the twist and the writhe structures on biopolymer is quantified in a computational manner. In this seminar, I enjoyed the discussion with audiences on the computational method and the definition of the twist and the writhe. Thank you so much! Reported by Hiroshi Yokota
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2022-09-01
Paper of the WeekWeek 1, September 2022
Title: Impact of Neutrino Cooling on Type-I X-ray Bursts and X-ray Superbursts Author: Akira Dohi, Nobuya Nishimura, Hajime Sotani, Tsuneo Noda, Helei Liu, Shigehiro Nagataki, Masa-aki Hashimoto arXiv: http://arxiv.org/abs/2208.14622v1 Title: Functional Renormalization Group Approach to Circuit Quantum Electrodynamics Author: Takeru Yokota, Kanta Masuki, Yuto Ashida arXiv: http://arxiv.org/abs/2208.14107v1 Title: Binary-coupling sparse SYK: an improved model of quantum chaos and holography Author: Masaki Tezuka, Onur Oktay, Enrico Rinaldi, Masanori Hanada, Franco Nori arXiv: http://arxiv.org/abs/2208.12098v1
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2022-08-30
Hot Topic
Featured articles on iTHEMS published in "Sugaku Tsushin"
iTHEMS was featured in the August volume of "Sugaku Tsushin" (Japanese magazine published by The Mathematical Society of Japan). Our colleagues, Tetsuo Hatsuda, Ade Irma Suriajaya, Yosuke Kubota, Hiroyasu Miyazaki and Yukimi Goto, have written essays on iTHEMS in the volume. Let's see mathematicians' thoughts on the iTHEMS atmosphere.
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2022-08-29
Press Release
Is it possible to shorten isolation of people infected with new coronavirus? -Development of a simulator to verify the timing of quarantine termination
Professor Shingo Iwami (Graduate School of Science, Nagoya University / Visiting Scientist, iTHEMS), in collaboration with Assistant Professor Keisuke Ejima (Indiana University, USA), has developed a new simulator (computer simulation) to verify when to end isolation of persons infected with a novel coronavirus (COVID-19) through antigen testing. This will allow us to propose a flexible and safe isolation strategy that can terminate isolation of COVID-19-infected patients as early as possible with negative results of a predetermined number of antigen tests. Isolation of infected patients is an important means of preventing the spread of infection. While prolonged isolation reduces the risk of secondary infection, it also places various burdens on the person being isolated and the society that supports them. Using the simulator they have developed, the research group has successfully calculated "the risk of (prematurely) terminating isolation of infectious patients" and "the duration of unnecessary isolation of patients who are no longer infectious (the burden associated with isolation)." As a result, we are now able to propose an appropriate isolation strategy that takes into account individual differences and uses antigen testing to simultaneously reduce risk and burden. As we enter the era of with-colonization, in which social activities are resumed and maintained while infection prevention measures are thoroughly implemented, the successful use of antigen testing will allow for the safe implementation of educational and social activities. In contrast to the current situation where different isolation standards based on clinical and epidemiological data and empirical rules are adopted in different countries, this study is expected to contribute to the establishment of flexible isolation guidelines based on mathematical models, which are required not only in Japan but also worldwide. For more details, please visit the Nagoya University research results dissemination site from the related link.
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2022-08-26
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Yosuke Mizuno on August 26, 2022
Dr. Yosuke Mizuno presented the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength 1.3 mm. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of ~50 micro-arcsecond. Using a large suite of numerical simulations, The EHT group demonstrated that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 million solar mass, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Their model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50 deg), as well as non-spinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way. In the seminar, Dr. Yosuke Mizuno focused on more theoretical interpretation and model comparison to understand the accretion flow properties nearby Sgr A*. Reported by Shigehiro Nagataki
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2022-08-26
Research News
RIKEN Research: Applying quantum speed limits to macroscopic systems
An expression for the maximum speed at which changes in macroscopic systems can occur has been derived by a theoretical physicist at RIKEN. This will deepen our understanding of quantum phenomena in systems that are not in equilibrium. One of the hardest aspects of quantum mechanics to grasp is the Heisenberg uncertainty principle that states that it is not possible to simultaneously pin down both the position and momentum of an object. In other words, the more precisely a particle’s position is determined, the broader the range of its possible momentum becomes (and vice versa). In 1945, two physicists, Leonid Mandelstam and Igor Tamm, focused on another type of the uncertainty relation, namely one between time and energy fluctuation, and showed that transitions in quantum systems don’t happen instantaneously; rather, the speed at which a transition occurs is capped by an amount determined by how much the energy of the system fluctuates. Many other so-called quantum speed limits have subsequently been derived, which have helped better understand the physics of quantum systems and have been useful in various quantum applications. But big problems arise when quantum speed limits are applied to macroscopic systems. “Previous quantum speed limits, which are useful for small systems, typically become meaningless for macroscopic transitions,” notes Ryusuke Hamazaki of the Nonequilibrium Quantum Statistical Mechanics RIKEN Hakubi Research Team. “For example, conventional quantum speed limits give an infinite upper bound for the speed of transitions in a gas made up of atoms.” To read more, please visit the related link.
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2022-08-25
Paper of the WeekWeek 4, August 2022
Title: High-energy neutrinos and gamma rays from winds and tori in active galactic nuclei Author: Susumu Inoue, Matteo Cerruti, Kohta Murase, Ruo-Yu Liu arXiv: http://arxiv.org/abs/2207.02097v2 Title: ALMA detection of parsec-scale blobs at the head of kiloparsec-scale jet in the nearby Seyfert galaxy NGC 1068 Author: Tomonari Michiyama, Yoshiyuki Inoue, Akihiro Doi, Dmitry Khangulyan arXiv: http://arxiv.org/abs/2208.08533v1
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2022-08-22
Hot Topic
Oita STEM Festa was held at Oita City
The Oita STEM Festa was held on 23 July 2022 at Oita city and Tetsuo Hatsuda from iTHEMS participated together with members from ADK Corporation. More than 50 high school students from Oita prefecture participated in Course B: "Let's deliver a message 1000 years from now using a black hole recorder” where the black hole recorder produced by the Useless Prototyping Studio was demonstrated. Also, the students were asked to write their Haiku to be recorderd in the black hole recorder. Over 150 high school students participated in the Oita STEM Festa. Course A: "Let's experience the lunar rover!, Course B: "Let's send a message 1000 years from now using a black hole recorder", Course C: "VR technology x solving social issues x SDGs", and Course D: "Let's think about jobs for Oita's future". iTHEMS was represented by Tetsuo Hatsuda and assistants Hitomi Wada and Chikako Ota contributed to the organisation of Course B on site.
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2022-08-18
Award
The paper by Dr. T. Hayata, Dr. Y. Hidaka and others has been selected as "Editors' Choice" of Progress of Theoretical and Experimental Physics
The Physical Society of Japan has announced that the paper entitled "Lattice Lindblad simulation" by Dr. Tomoya Hayata Itou (iTHEMS Visiting Scientist/Keio Univ.), Dr. Yoshimasa Hidaka (iTHEMS Visiting Scientist/KEK) and their collaborator has been selected as the Editors' Choice in Progress of Theoretical and Experimental Physics.
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2022-08-18
Hot Topic
The book “An introduction to deep learning” written by Dr. Masato Taki was recently featured in the column “La Toccata” by Dr. T. Otsuki
Dr. Masato Taki (iTHEMS Visiting Research Scientist/ Rikkyo University) wrote the book “An introduction to deep learning” while he was at iTHEMS. The book was recently featured in the column “La Toccata” by Dr. T. Otsuki (Sophia University) in the journal BUTSURI published by the Physical Society of Japan in Aug. 2022. The features of this textbook are: 1. it understands what readers with a physics background will find difficult; 2. the examples are neither too simple nor too obvious so that the reader feels he/she understands by reading the examples; 3. the volume is reasonable; 4. each section is divided into small sections so that it is suitable for the reading club, and 5. the appendices are also very informative. Recommended for those who want to learn deep learning from scratch and for those who want to organize a reading club.
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2022-08-11
Paper of the WeekWeek 2, August 2022
Title: Calibration of nuclear charge density distribution by back-propagation neural networks Author: Zu-Xing Yang, Xiao-Hua Fan, Tomoya Naito, Zhong-Ming Niu, Zhi-Pan Li, Haozhao Liang arXiv: http://arxiv.org/abs/2205.15649v2 Title: Stability against three-body clustering in one-dimensional spinless p-wave fermions Author: Yixin Guo, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2208.03654v1 Title: Thermal Ringdown of a Kerr Black Hole: Overtone Excitation, Fermi-Dirac Statistics and Holography Author: Naritaka Oshita arXiv: http://arxiv.org/abs/2208.02923v1 Title: Tricritical phenomena in holographic chiral phase transitions Author: Masataka Matsumoto arXiv: http://arxiv.org/abs/2208.02605v1
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2022-08-08
Hot Topic
iTHEMS Science Outreach Workshop 2022 was held on July 29-31, 2022
On July 29-31, we had Meeting on Outreach of RIKEN iTHEMS 2022 @Kobe & Zoom. This year the meeting was hosted by Suuri Cool Kobe and the venue was the auditorium (8F) + the cafeteria (6F) of Kobe Integrated Innovation Building (IIB). This meeting was hit by the big growth of infected population by Covid-19 omicron BA.5. However, under careful preparation and precaution taken, 27 people participated at Kobe IIB and 24 more by zoom. There were 11 talks at the venue and 6 talks by zoom. 4 talks were by members of iTHEMS explaining recent development in various fields in sciences. 3 talkes were from universities on different aspects of research or fostering young researchers. 10 talks were given by journalists. There were also 3 posters (2 on research and 1 on a monthly academic magazine), in addition, the Black Hole Reacorder was exhibited at the cafeteria. The participants consist of 9+10 members from RIKEN, 6+4 from universities and 12+10 journalists (at venue + by zoom). By the success of this meeting, we hope the continuation of Journalist in residence program and this workshop next year.
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2022-08-08
Seminar Report
iTHEMS Math Seminar by Prof. Narutaka Ozawa on August 2, 2022
On August 2, Professor Narutaka Ozawa (RIMS, Kyoto University) gave a talk entitled "Product Replacement Algorithm, Semidefinite Programming, and Operator Algebras" in the iTHEMS Math Seminar. He elegantly explained how his recent study on Kazhdan's property (T) ties the field of functional analysis/operator algebras and that of computer sciences. Reported by Michiya Mori
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2022-08-05
Seminar Report
iTHEMS Math Seminar by Dr. Hokuto Konno on July 15, 2022
On July 15, there was a math seminar by Professor Konno. He gave an introductory talk on the Seiberg-Witten Floer homotopy type. Reported by Keita Mikami
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2022-08-04
Paper of the WeekWeek 1, August 2022
Title: Stochastic failure of cell infection post viral entry: Implications for infection outcomes and antiviral therapy Author: Christian Quirouette, Daniel Cresta, Jizhou Li, Kathleen P. Wilkie, Haozhao Liang, Catherine A. A. Beauchemin arXiv: http://arxiv.org/abs/2208.00637v1 Title: Structure-preserving numerical methods for constrained gradient flows of planar closed curves with explicit tangential velocities Author: Tomoya Kemmochi, Yuto Miyatake, Koya Sakakibara arXiv: http://arxiv.org/abs/2208.00675v1 Title: The eco-evolutionary dynamics of prior selfing rates promote coexistence without niche partitioning under conditions of reproductive interference Author: Koki R. Katsuhara, Yuuya Tachiki, Ryosuke Iritani, Atushi Ushimaru Journal Reference: Journal of Ecology, Volume109, Issue11, p.3916-3928 (2021) doi: https://doi.org/10.1111/1365-2745.13768 Title: Partitioning the temporal changes in abundance-based beta diversity into loss and gain components Author: Shinichi Tatsumi, Ryosuke Iritani, Marc W. Cadotte Journal Reference: Methods in Ecology and Evolution (2022) doi: https://doi.org/10.1111/2041-210X.13921 Title: Black Hole as a Bound State of Semi-classical Degrees of Freedom Author: Yuki Yokokura arXiv: http://arxiv.org/abs/2207.14274v1
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2022-08-04
Seminar Report
Seminar by Dr. Xavier Roca-Maza on August 3, 2022
As a part of the RCNP domestic workshop on low-energy nuclear physics and high-energy astrophysics (RCNP研究会「低エネルギー核物理と高エネルギー天文学で読み解く中性子星」), the special seminar entitled "How does subatomic matter organize itself? A low-energy nuclear physics perspective" was given by Prof. Xavier Roca-Maza in U. Milan. This seminar is supported by Gravitational Wave and Equation of State Working Group (GW-EOS WG), RIKEN iTHEMS Program. The equation of state (EoS) of nuclear matter is one of the essential things in nuclear physics. There have been many attempts to determine parameters characterizing the EoS experimentally, which have become paid attention more. He introduced various attempts and theoretical mechanisms, including cutting-edge proposals. More than 80 participants attended the seminar, including from the foreign country. Reported by Tomoya Naito
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2022-07-29
Seminar Report
iTHEMS Colloquium by Prof. Yasunori Nomura on July 26, 2022
Prof. Yasunori Nomura, the director of the Berkeley Center for Theoretical Physics, the University of California, Berkeley, visited iTHEMS and gave a colloquium entitled “From the Black Hole Conundrum to the Structure of Quantum Gravity” on July 26th. Prof. Nomura started the colloquium by explaining that the two pillars of modern physics, quantum mechanics and general relativity are actually at odds with each other, but each of them usually governs a different domain of physical phenomena, thus obscuring the incompatibility. The focus of the colloquium lies on one of the areas where both quantum mechanics and general relativity become equally important, namely quantum theory of black holes. Prof. Nomura illustrated how the famous phenomenon of black holes discovered by Stephen Hawking, Hawking radiation leads to so-called information paradox, in which the conservation the probability appears to be violated during the process of the radiation from the horizon. He went on to describe the key ingredients in solving the paradox, which are the concept of holography, the stretched horizon, and AdS/CFT correspondence. In the latter part of the colloquium, Prof. Nomura pedagogically showed the audience the most recent development in the study of the information paradox. The calculation including the contribution from “wormholes” was shown to reproduce the Page curve implying the recovery of the lost probability. The same calculation was also explained through formalism which was developed by Prof. Nomura himself. He concluded with the message that the study of the black hole conundrum is thus revealing the structure of quantum gravity, which involves with a wide range of various research fields such as high energy physics and astrophysics, quantum information science, and many-body physics. The colloquium was taken place at the 2F Large Meeting Room of RIBF Building and was attended by a limited number of audience in person due to the wide spreading of COVID-19, but more than eighty people joined through zoom. Reported by Tsukasa Tada
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2022-07-28
Paper of the WeekWeek 5, July 2022
Title: Ceratozamia schiblii (Zamiaceae): A new cycad species from the eastern mountains of Oaxaca, Mexico Author: Miguel Angel Pérez-Farrera, José Said Gutiérrez-Ortega, Timothy J. Gregory, Jeffrey Chemnick, Silvia Salas-Morales, Michael Calonje, Pedro Díaz-Jiménez Journal Reference: Taxonomy 2(3):324-338 (2022) doi: https://doi.org/10.3390/taxonomy2030025 Title: New developments in relativistic magnetohydrodynamics Author: Koichi Hattori, Masaru Hongo, Xu-Guang Huang arXiv: http://arxiv.org/abs/2207.12794v1
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2022-07-26
Hot Topic
iTHEMS and RIKEN-Berkeley Center is featured in RIKEN at a Glance 2022
RIKEN's pamphlet "RIKEN at a Glance 2022" features iTHEMS and the newly opened RIKEN-Berkeley Center. Please see the related link for details.
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2022-07-25
Seminar Report
iTHEMS Biology Seminar by Dr. Namiko Mitarai on July 7, 2022
Dr. Namiko Mitarai (Niels Bohr Institute) gave us an amazing talk in the biology seminar. She told us about the collaborative works with experimental biologists on a microbial world. Some viruses that infect bacteria are known to provide immunity to infection by the same virus. According to her, no-immune bacteria can be protected from infection when the ratio of immune bacteria is substantially high in the population, which reminds us of our current cases for Covid-19. Interestingly, the metabolic state of host (bacteria) also affects the virus infection. The talk was very very exciting. In the end of her seminar, she also showed us the tips for the successful collaboration with experimental biologists: (1) We (theorists) should care about them. (2) They (experimental biologists) should care about us. During and after the talk, there were lively discussion between the speaker and iTHEMS researchers. Thanks Mitarai-san!! Reported by Gen Kurosawa
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2022-07-21
Research News
RIKEN NEWS: Collective Motion in Atomic World
It is mysterious to see a large flock of starlings or sardines change its direction simultaneously and collectively. Similar phenomena have been observed in smaller systems like cells in our body. Using computer simulations, Dr. Kyosuke Adachi (Special Postdoctoral Researcher) has theoretically found that such collective behavior can occur in the even smaller atomic world. To read more, please visit the related link.
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2022-07-21
Paper of the WeekWeek 4, July 2022
Title: S-transformations for CFT_2 as linear mappings from closed to open sector linear spaces Author: Xun Liu arXiv: http://arxiv.org/abs/2207.08480v1
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2022-07-15
Seminar Report
iTHEMS Biology Seminar by Dr. Jun-nosuke Teramae on July 14, 2022
In this week’s biology seminar, we were very happy to have Dr. Jun-nosuke Teramae from Kyoto University to tell us about the mysterious stochastic behavior of neurons and synapses in the brain. Many biological experimental observations are reported. However, how this stochasticity is beneficial for computation and learning in the brain remains largely unknown. Dr. Teramae presented his work on developing an efficient learning algorithm inspired by this brain behavior. The algorithm is based on Gibbs-sampling which allow us to efficiently obtain high-dimensional sampling results. The algorithm shows similar stochastic behavior of the brain, which other machine leaning algorithms doesn’t show. In the end, Dr. Teramae briefly showed us the algorithm enables us to reproduce the recently discovered efficient power-law coding in the cortex. Even the seminar time is ended, the discussion continued for a long while. The seminar inspired many open questions on brain behavior and learning algorithms, both for the speaker and the audiences. We look forward to further development on the subjects. We thank Dr. Jun-nosuke Teramae and everyone joined the seminar. Reported by Yingying Xu
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2022-07-15
Seminar Report
Quantum Matter Seminar by Dr. Ken Shiozaki on July 12, 2022
Prof. Ken Shiozaki gave a seminar about adiabatic cycles of quantum spin systems. Topological phases of matter without ground state degeneracy are known as inevitable phases. In the literature, their topological properties have been well-studied in free-fermion and many-body systems. The speaker started with the transverse-field Ising model and the Rice-Mele model to demonstrate the pumping of the 1D chain in an adiabatic cycle. He then generalized the concept to cover broader systems, including general spatial dimensions and generic models with any onsite symmetry, such as time-reversal, Z2 Ising, and U(1). He demonstrated that one can classify adiabatic cycles of a spin model, which can be characterized by a Z2 topological invariant. This talk showed that symmetry-protected topological phases emerge by performing an adiabatic cycle. Reported by Chen-Hsuan Hsu (YITP, Kyoto University)
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2022-07-14
Paper of the WeekWeek 3, July 2022
Title: Spatially resolved study of the SS 433/W50 west region with Chandra: X-ray structure and spectral variation of non-thermal emission Author: Kazuho Kayama, Takaaki Tanaka, Hiroyuki Uchida, Takeshi Go Tsuru, Takahiro Sudoh, Yoshiyuki Inoue, Dmitry Khangulyan, Naomi Tsuji, Hiroaki Yamamoto arXiv: http://arxiv.org/abs/2207.05924v1 Title: Constraining primordial curvature perturbations using dark matter substructure Author: Shin'ichiro Ando, Nagisa Hiroshima, Koji Ishiwata arXiv: http://arxiv.org/abs/2207.05747v1 Title: QFT approach to dressed particle processes in preheating and non-perturbative mechanism in kinematically-forbidden regime Author: Hidetoshi Taya, Yusuke Yamada arXiv: http://arxiv.org/abs/2207.03831v1
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2022-07-13
Seminar ReportiTHEMS Theoretical Physics Seminar by Prof. Hiroshi Suzuki on July 5, 2022
The iTHEMS-phys intensive lecture was held on July 5 and 6, 2022. The speaker is Prof. Hiroshi Suzuki at Kyushu University. The title is “Gradient flow exact renormalization group.” Wilson’s exact renormalization group (ERG), which tells how a system changes under the scale transformation, provides a fundamental framework to define quantum field theory even beyond the perturbation theory. It has, however, been known that it is difficult to preserve a manifest gauge symmetry in ERG because of the usage of the momentum cutoff in ERG. Recently, he has proposed a possible modification of ERG, the gradient flow exact renormalization (GFERG), which preserves a manifest gauge symmetry being based on a gauge-covariant diffusion equation. He has explained the basic idea and properties of GFERG. He has also presented a possible application of GFERG to the consideration of the axial anomaly. The lecture was held via Zoom. There were about 30 participants from iTHEMS and other universities. The participants enjoyed fruitful discussions throughout the lecture. Reported by Kengo Kikuchi
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2022-07-07
Paper of the WeekWeek 2, July 2022
Title: Nuclear Many-Body Effect on Particle Emissions Following Muon Capture on ^{28}Si and ^{40}Ca Author: Futoshi Minato, Tomoya Naito, Osamu Iwamoto arXiv: http://arxiv.org/abs/2207.02514v1 Title: A symmetry principle for gauge theories with fractons Author: Yuji Hirono, Minyoung You, Stephen Angus, Gil Young Cho arXiv: http://arxiv.org/abs/2207.00854v1 Title: Velocity of Sound beyond the High-Density Relativistic Limit from Lattice Simulation of Dense Two-Color QCD Author: Kei Iida, Etsuko Itou arXiv: http://arxiv.org/abs/2207.01253v1 Title: A note on generalized Thurston--Bennequin inequalities Author: Nobuo Iida, Hokuto Konno, Masaki Taniguchi arXiv: http://arxiv.org/abs/2207.00229v1
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2022-07-06
Seminar Report
iTHEMS Biology Seminar by Mr. Keiichi Morita on June 23, 2022
I talk about how evolution of sexual traits such as ornaments of guppies can affect coexistence of two closely related species. First, I introduce "reproductive interference," sexual interaction driving evolution of sexual traits. Second, I show how to formulate population dynamics of two closely related species with reproductive interference. Next, I introduce mathematical modeling of quantitative genetics in order to formulate trait evolution. Finally, I show results of analysis and simulation by combining population dynamics and evolution (i.e., eco-evolutionary feedbacks). In future works, I should the effect of costs of evolution or the other species. Thank you for your listening and giving me comments! Reported by Keiichi Morita
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2022-07-05
Seminar Report
Quantum Matter Seminar by Dr. Thore Posske on June 30, 2022
Dr. Thore Posske from the University of Hamburg gave an online seminar about controlling topological quantum effect in spin systems by manipulating the boundary. He first introduced the idea that topology can connect multiple subfields in physics and then showed how a 1D spin chain can be controlled to form a helix or the ground state by manipulating the evolution of the two chain ends. Since the different quantum states can be controlled by the boundary, this is a potential platform for quantum computing to generate distinct quantum states. Furthermore, the boundary idea was extended to 2D spin systems. By properly changing the spins on the edges, a skyrmion can emerge. In the end, the speaker talked about an experimental approach to distinguishing the topological phases in systems with periodic boundary conditions by multi-pulse spectroscopy, and applied these ideas to 1D topological superconductors. Reported by Thore Posske (University of Hamburg) and Ching-Kai Chiu
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2022-07-04
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Mr. Tomoki Matsuoka on July 1, 2022
Mr. Tomoki Matsuoka gave an excellent talk on the long-term evolution of a supernova remnant hosting a double neutron star binary. He presented that stellar mass loss is one of the crucial elements determining the fate of core-collapse supernovae progenitors (SNe). Since the material released from the progenitor will be distributed as circumstellar medium (CSM), it can also influence the subsequent evolution of the SN or supernova remnant (SNR). Despite its importance, mass loss histories predicted by stellar evolution models have not been incorporated with modeling for SNRs. As a first step, he investigated the dynamical evolution of an ultra-stripped supernova remnant (USSNR), which originated from a core-collapse SN explosion proposed to be a candidate formation site of a double neutron star binary. By accounting for the mass-loss history of the progenitor binary using a model developed by a previous study, he constructed the large-scale structure of the CSM up to a radius ∼100 pc. Then, he simulated the explosion and subsequent evolution of a USSN surrounded by such a CSM environment. He found that the CSM encompasses a vast region characterized by a hot plasma with a temperature ∼10^8 K located around the termination shock of the wind from the progenitor binary (∼10 pc), and the USSNR blast wave is drastically weakened while penetrating through this hot plasma. Radio continuum emission from a young USSNR is sufficiently bright to be detectable if it inhabits our galaxy but faint compared to the observed Galactic SNRs. In this seminar, he talked about the background of the connection between the models for stellar evolution and SNRs, the details of his methods, and future prospects very well. Reported by Shigehiro Nagataki
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2022-07-04
Seminar Report
iTHEMS Biology Seminar by Dr. Margie Mayfield on June 30, 2022
Dr. Margie Mayfield (University of Melbourne) gave us a fantastic talk in the special biology seminar, held in a hybrid style at Okouchi Hall. She told us about comparative work on theoretical models and data in wild flowers. We really thank Margie on her great talk, especially despite her very tight schedule in Japan. Thank you Margie! I look forward to seeing you soon in person! Reported by Ryosuke Iritani
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2022-07-04
Person of the Week
Self-introduction: Christy Kelly
Hi, I'm Christy Kelly. I studied physics for my undergraduate degree in London before moving to Edinburgh to do a PhD in theoretical physics at Heriot-Watt university, completed in early 2022. I have now joined iTHEMS as an SPDR. I am interested in gravity, especially coarse aspects of gravity that persist in the absence of differentiable structure; in more physical terms, we can perhaps think of this as gravity in regimes where quantum fluctuations become significant. In such regimes, basic mathematical tools such as calculus are no longer valid and it becomes nontrivial how to characterise even such fundamental notions as curvature. To get around this problem, I hope to exploit the recently flourishing mathematical field of optimal transport theory, which has already become a paradigm for the study of low regularity Riemannian geometry and has seen some very exciting recent developments in the Lorentzian case. Unexpected connections to different fields of physics also arise naturally in the optimal transport theoretic framework: for instance, the Einstein equations can be characterised in terms of the convexity/concavity properties of certain entropy functionals along choice trajectories in spacetime. Optimal transport theory also provides a notion of curvature for networks which has proved of some structural significance; I hope to also take this line of research forward during my time here at iTHEMS.
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2022-06-30
Paper of the WeekWeek 5, June 2022
Title: Role of the effective range in the density-induced BEC-BCS crossover Author: Hiroyuki Tajima, Haozhao Liang arXiv: http://arxiv.org/abs/2206.12599v1
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2022-06-28
Research News
RIKEN Research: Flitting between the wings of a butterfly
Just making small tweaks to certain variables could potentially modify extreme weather events such as sudden downpours, computer simula- tions by two RIKEN researchers have shown. Scientists have long desired to develop ways to control the weather. Research in this area has intensified due to climate change, which is giving rise to more extreme weather events. Present methods for modifying the weather have limited success. Seeding the atmosphere can induce rain, but only when the atmosphere is already in a state where it might rain. Geoen- gineering projects have been envisioned, but they have yet to be conducted due to concerns about unpredicted long-term effects. As a promising approach, Takemasa Miyoshi and Qiwen Sun, both of the RIKEN Center for Computational Science, have looked to chaos theory to assess the possibility of mitigating weather events such as torrential rain by making small changes. Instead of con- sidering the weather system in all its complexity, they focused on a far simpler system—the butterfly attractor. To read more, please see related links.
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2022-06-28
Research News
RIKEN Research: Worming out of the black-hole information paradox
RIKEN physicist and two colleagues have found that a wormhole—a theoretical bridge connecting distant regions of the Universe—may help to shed light on the mystery of what happens to information about matter consumed by black holes. Einstein’s theory of general relativity predicts that nothing that falls into a black hole can escape its clutches. But in the 1970s, Stephen Hawking calculated that black holes should emit radiation when quantum mechanics, the theory governing the microscopic realm, is considered. “This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet,” explains Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences. To read more, please see related links.
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2022-06-27
Seminar Report
iTHEMS Math Seminar by Dr. Shou Yoshikawa on June 10, 2022
On June 10, Shou Yoshikawa gave an introductory talk on his research field. He started his talk by explaining what is an algebraic geometry in mixed characteristic. He then explained some recent results on this subject. Reported by Keita Mikami
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2022-06-23
Seminar Report
Quantum Matter Seminar by Dr. Nobuyuki Okuma on June 21, 2022
Quantum Matter Study Group invited Prof. Nobuyuki Okuma to give an online seminar about non-Hermitian topological phases. The seminar started with a succinct introduction to non-Hermitian matrices. Different from Hermitian systems, the energy spectra now become complex numbers, the bra and ket states become inequivalent, and the Hamiltonians are not always diagonalizable, leading to the emergence of exceptional points. Taking the Hatano-Nelson model as an example, the speaker studied the 1D chain with the imaginary gauge transformation and showed that the spectra strongly depend on the boundary conditions (being periodic or open). Furthermore, distinct from end modes in Hermitian topological insulators, skin effect arises in non-Hermitian systems, with skin modes accumulating in one end of the chain. He further showed that this skin effect also exhibits topological nature and can be generalized to either higher-dimensional systems or to other non-Hermitian systems with Z2 topological invariants. Reported by Chen-Hsuan Hsu (YITP) and Ching-Kai Chiu
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2022-06-21
Seminar Report
iTHEMS Biology Seminar by Dr. Mitsusuke Tarama on June 16, 2022
On June 16th, Dr. Tarama gave us an interesting talk about the physical modeling of self-organization in the chick embryo. He first introduced several beautiful patterns in biology such as stripes of pigment cells of Zebrafish. He then explained a recent observation of the dynamical meshwork structure of chick mesodermal cells, which is the direct motivation of his theoretical work. He showed how the intercellular interactions and shape deformation of cells can produce the dynamical meshwork structure, by physical modeling and application of the persistent homology as a useful tool. We are really grateful to Dr. Tarama for his comprehensive talk from both experimental and theoretical sides. Reported by Kyosuke Adachi
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2022-06-20
Seminar Report
Math-Phys Seminar by Dr. Daisuke Yoshida on June 16, 2022
Dr. Daisuke Yoshida first motivated the expectation that the true quantum gravity, whatever its form turns out to be, should be free from singularities in the universe. The "singularity theorem" by Penrose states that a spacetime singularity arises under a set of certain assumptions. Flipping the argument around, if one admits that singularities are absent in our universe, at least one of the assumptions in the theorem needs to be abandoned. Dr. Yoshida discussed general properties that a non-singular universe must satisfy in order to avoid the singularity theorem. In particular, he found and explained that the universe must be, in some sense, smaller than the corresponding closed de Sitter spacetime. His talk stimulated the audience, and they continued discussions for long after his seminar. Reported by Ryo Namba
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2022-06-16
Paper of the WeekWeek 3, June 2022
Title: Reflected Entropy in Boundary/Interface Conformal Field Theory Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.04630v1
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2022-06-09
Seminar Report
iTHEMS Biology Seminar by Dr. José Said Gutiérrez-Ortega on June 2, 2022
In this talk, I mentioned how both geographic isolation and natural selection may influence the way how species can be originated. I made emphasis in a general pattern that suggests that tropical species are more likely than high-latitude species to evolve while retaining the niche of their ancestors; a process called “niche conservatism”. To demonstrate this pattern, I showed the recent results of my own empirical research on the cycad genus Ceratozamia from Mexico: species at lower latitudes evolved niches less differentiated than expected from a Brownian Motion model (an evidence of niche conservatism), and high-latitude species evolved niches more differentiated than expected (an evidence of niche divergence). I hypothesize that both “niche conservatism” and “niche divergence” are not opposed processes as usually thought in ecology, but are part of a same general process. The implementation of models to predict how phylogenetic and ecological factors interplay in the formation of species along the latitudinal gradient may explain the pattern at the global level. The discussion on this topic allowed identifying that the latitude-associated variation of biodiversity richness seems to be analogous to thermodynamic models: a higher energy availability in the tropics will make biological groups to evolve different ways (species) to exploit that energy. Reported by José Said Gutiérrez-Ortega
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2022-06-09
Paper of the WeekWeek 2, June 2022
Title: Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang, Changqing Jin, Ching-Kai Chiu, Stephen J. Pennycook, Ziqiang Wang, Hong-Jun Gao Journal Reference: Nature (2022) doi: https://doi.org/10.1038/s41586-022-04744-8 Title: Observing Supernova Neutrino Light Curves with Super-Kamiokande. III. Extraction of Mass and Radius of Neutron Stars from Synthetic Data Author: Yudai Suwa, Akira Harada, Masayuki Harada, Yusuke Koshio, Masamitsu Mori, Fumi Nakanishi, Ken'ichiro Nakazato, Kohsuke Sumiyoshi, Roger A. Wendell arXiv: http://arxiv.org/abs/2204.08363v1 Title: Lindbladian Many-Body Localization Author: Ryusuke Hamazaki, Masaya Nakagawa, Taiki Haga, Masahito Ueda arXiv: http://arxiv.org/abs/2206.02984v1 Title: Semiclassical Gravity from Averaged Boundaries in two-dimensional BCFTs Author: Yuya Kusuki arXiv: http://arxiv.org/abs/2206.03035v1 Title: Evaluations of uncertainties in simulations of propagation of ultrahigh-energy cosmic-ray nuclei derived from microscopic nuclear models Author: E. Kido, T. Inakura, M. Kimura, N. Kobayashi, S. Nagataki, N. Shimizu, A. Tamii, Y. Utsuno arXiv: http://arxiv.org/abs/2206.03447v1 Title: Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation-Hydrodynamics Code Author: Ryuichiro Akaho, Akira Harada, Hiroki Nagakura, Wakana Iwakami, Hirotada Okawa, Shun Furusawa, Hideo Matsufuru, Kohsuke Sumiyoshi, Shoichi Yamada arXiv: http://arxiv.org/abs/2206.01673v1 Title: Semi-analytical frameworks for subhalos from the smallest to the largest scale Author: Nagisa Hiroshima, Shin'ichiro Ando, Tomoaki Ishiyama arXiv: http://arxiv.org/abs/2206.01358v1 Title: Ring isomorphisms of type II_\infty locally measurable operator algebras Author: Michiya Mori arXiv: http://arxiv.org/abs/2206.00875v1 Title: Universal van der Waals force between heavy polarons in superfluids Author: Keisuke Fujii, Masaru Hongo, Tilman Enss arXiv: http://arxiv.org/abs/2206.01048v1
217 news in 2022