News
161 news in 2023

20231207
Paper of the WeekWeek 2, December 2023
Title: Improved realspace parallelizable matrixproduct state compression and its application to unitary quantum dynamics simulation Author: RongYang Sun, Tomonori Shirakawa, Seiji Yunoki arXiv: http://arxiv.org/abs/2312.02667v1 Title: Oliver Curvature Bounds for the Brownian Continuum Random Tree Author: Christy Kelly arXiv: http://arxiv.org/abs/2312.01894v1

20231205
Seminar ReportJoint RIKEN/N3AS Workshop on MultiMessenger Astrophysics on November 26, 2023
The joint RIKENBerkeley workshop on MultiMessenger Astrophysics was held on Nov.26 on the Big Island in Hawaii. More than 40 participants from both sides of the Pacific gathered to discuss nuclear and particle astrophysics. The photo shows a talk by Nobuya Nishimura (RIKEN Nishina Center) on the nucleosynthesis of heavyelements in supernovae and neutron star mergers, chaired by Wick Haxton (UC Berkeley/iTHEMS). Lively discussions took place during the lectures and poster session. Reported by Tetsuo Hatsuda

20231130
Paper of the WeekWeek 5, November 2023
Title: Study on Lambda(1405) in the flavor SU(3) limit in the HAL QCD method Author: Kotaro Murakami, Sinya Aoki arXiv: http://arxiv.org/abs/2311.17421v1 Title: Searching for High Frequency Gravitational Waves with Phonons Author: Yonatan Kahn, Jan SchütteEngel, Tanner Trickle arXiv: http://arxiv.org/abs/2311.17147v1 Title: Endtoend complexity for simulating the Schwinger model on quantum computers Author: Kazuki Sakamoto, Hayata Morisaki, Junichi Haruna, Etsuko Itou, Keisuke Fujii, Kosuke Mitarai arXiv: http://arxiv.org/abs/2311.17388v1 Title: Towards complete characterization of topological insulators and superconductors: A systematic construction of topological invariants based on AtiyahHirzebruch spectral sequence Author: Seishiro Ono, Ken Shiozaki arXiv: http://arxiv.org/abs/2311.15814v1 Title: Speed of sound exceeding the conformal bound in dense 2color QCD Author: Etsuko Itou, Kei Iida arXiv: http://arxiv.org/abs/2311.15259v1 Title: New configuration set of HAL QCD collaboration Author: Etsuko Itou for HAL QCD collaboration arXiv: http://arxiv.org/abs/2311.15522v1 Title: Supernovae Ia and GammaRay Bursts together shed new lights on the Hubble constant tension and cosmology Author: M. G. Dainotti, B. De Simone, G. Montani, E. Rinaldi, M. Bogdan, K. M. Islam, A. Gangopadhyay Journal Reference: PoS(ICRC2023)1367 arXiv: http://arxiv.org/abs/2309.05876v1 Title: Parameter estimation by learning quantum correlations in continuous photoncounting data using neural networks Author: Enrico Rinaldi, Manuel González Lastre, Sergio García Herreros, Shahnawaz Ahmed, Maryam Khanahmadi, Franco Nori, Carlos Sánchez Muñoz arXiv: http://arxiv.org/abs/2310.02309v1 Title: GRB Optical and Xray Plateau Properties Classifier Using Unsupervised Machine Learning Author: Shubham Bhardwaj, Maria G. Dainotti, Sachin Venkatesh, Aditya Narendra, Anish Kalsi, Enrico Rinaldi, Agnieszka Pollo Journal Reference: MNRAS, Volume 525, Issue 4, pp.52045223, November 2023 doi: https://doi.org/10.1093/mnras/stad2593 arXiv: http://arxiv.org/abs/2308.14288v4 Title: Estimating truncation effects of quantum bosonic systems using sampling algorithms Author: Masanori Hanada, Junyu Liu, Enrico Rinaldi, Masaki Tezuka Journal Reference: Mach. Learn.: Sci. Technol. 4 045021, 2023 doi: https://doi.org/10.1088/26322153/ad035c arXiv: http://arxiv.org/abs/2212.08546v2 Title: Approximate Autonomous Quantum Error Correction with Reinforcement Learning Author: Yexiong Zeng, ZhengYang Zhou, Enrico Rinaldi, Clemens Gneiting, Franco Nori Journal Reference: Phys. Rev. Lett. 131, 050601 (2023) doi: https://doi.org/10.1103/PhysRevLett.131.050601 arXiv: http://arxiv.org/abs/2212.11651v2 Title: MEET: A Monte Carlo ExplorationExploitation Tradeoff for Buffer Sampling Author: Julius Ott, Lorenzo Servadei, Jose ArjonaMedina, Enrico Rinaldi, Gianfranco Mauro, Daniela Sánchez Lopera, Michael Stephan, Thomas Stadelmayer, Avik Santra, Robert Wille arXiv: http://arxiv.org/abs/2210.13545v2

20231126
Seminar ReportABBLiTHEMS Joint Astro Seminar by Derek Beattie Inman on November 24, 2023
Cosmological observations have led to an extremely precise understanding of the largescale structure of the Universe. A common assumption is to extrapolate largescale properties to smaller scales; however, whether this is correct or not is unknown and many wellmotivated early Universe scenarios predict substantially different structure formation histories. In this seminar Derek discussed two scenarios where nonlinear structures form much earlier than is typically assumed. In the first case, the initial fluctuations are enhanced on small scales leading to either primordial black holes clusters or WIMP minihalos right after matterradiation equality. In the second, Derek showed that an additional attractive dark force leads to structure formation even in the radiation dominated Universe. Derek furthermore discussed possible observations of such early structure formation including changes to the cosmic microwave background, dark matter annihilation, and when the first galaxies form. Reported by Shigehiro Nagataki

20231123
Paper of the WeekWeek 4, November 2023
Title: A KohnSham Scheme Based Neural Network for Nuclear Systems Author: ZuXing Yang, XiaoHua Fan, ZhiPan Li, Haozhao Liang Journal Reference: Phys. Lett. B 840, 137870 (2023) doi: https://doi.org/10.1016/j.physletb.2023.137870 arXiv: http://arxiv.org/abs/2212.02093v2 Title: A thresholdtype algorithm to the gradient flow of the CanhamHelfrich functional Author: Katsuyuki Ishi, Yoshihito Kohsaka, Nobuhito Miyake, Koya Sakakibara arXiv: http://arxiv.org/abs/2311.13155v1 Title: Magnonic spin current shot noise in an itinerant Fermi gas Author: Tingyu Zhang, Hiroyuki Tajima, Haozhao Liang arXiv: http://arxiv.org/abs/2311.12383v1 Title: Quantum Simulation of Finite Temperature Schwinger Model via Quantum Imaginary Time Evolution Author: Juan W. Pedersen, Etsuko Itou, RongYang Sun, Seiji Yunoki arXiv: http://arxiv.org/abs/2311.11616v1 Title: Firstorder bulk transitions in large$N$ lattice YangMills theories using the density of states Author: Felix Springer, David Schaich, Enrico Rinaldi arXiv: http://arxiv.org/abs/2311.10243v1 Title: Sexual antagonism in sequential hermaphrodites Author: Thomas Hitchcock, Andy Gardner Journal Reference: Proc. R. Soc. B 290: 20232222 doi: https://doi.org/10.1098/rspb.2023.2222

20231116
Person of the WeekSelfintroduction: Dongwook Ghim
I am a theoretical physicist working on highenergy physics, HEPTH. More precisely, I am interested in the spectral problems of strongly coupled gauge theory. The infamous quark confinement of Quantum Chromodynamics and the mass gap generation of YangMills theory are the most wellknown spectral problems involving strongly coupled gauge theory. I mainly use two orthogonal toolkits to tackle such problems; supersymmetry and quantum simulation. I have worked on the computation of the twisted partition function of supersymmetric gauge theories, which appear in the string theory context, showing a strong relation with the geometry of CalabiYau manifolds. Simultaneously, I am eager to develop a quantum algorithm that can capture the spectra of gauge theories, without the aid of supersymmetry. The latter targets lowdimensional lattice gauge theory in practice. But I dream of capturing the physics of three or fourdimensional gauge theory on the quantum processor near future. I look forward to a fruitful collaboration with people in iTHEMS, RIKEN.

20231116
Paper of the WeekWeek 3, November 2023
Title: Magneticcoupled electronic landscape in bilayerdistorted titaniumbased kagome metals Author: Yong Hu, Congcong Le, Long Chen, Hanbin Deng, Ying Zhou, Nicholas C. Plumb, Milan Radovic, Ronny Thomale, Andreas P. Schnyder, JiaXin Yin, Gang Wang, Xianxin Wu, Ming Shi arXiv: http://arxiv.org/abs/2311.07747v1 Title: The phylogenetic reconstruction of the Neotropical cycad genus Ceratozamia (Zamiaceae) reveals disparate patterns of niche evolution Author: José Said GutiérrezOrtega, Miguel Angel PérezFarrera, Ayumi Matsuo, Mitsuhiko P. Sato, Yoshihisa Suyama, Michael Calonje, Andrew P. Vovides, Tadashi Kajita, Yasuyuki Watano Journal Reference: Molecular Phylogenetics and Evolution doi: https://doi.org/10.1016/j.ympev.2023.107960

20231113
Seminar ReportiTHEMS Math Seminar by Möller Sven on September 19, 2023
He gave a talk on classification of holomorphic vertex operator superalgebra with central charge 24 using the method of adjacency graphs. Reported by Yuto Moriwaki

20231109
Seminar ReportiTHEMS Biology Seminar by José Said GutiérrezOrtega on November 7, 2023
In Nov 7, our colleague Dr. José Said GutiérrezOrtega gave a fantastic talk about the most conspicuous pattern of correlation between environment/geography and biodiversity. For many species, including birds and mammals, it has been known that biodiversity is higher in the tropics and lower in the areas with high latitude, but we do not why. In his talk, José addressed this big biodiversity problem using his accurate and various data of a plant, called fern (i.e. “shida” in Japanese) throughout the American continent which is the ideal system to study the problem according to him. During and after the talk, there were lively discussions about this interesting pattern, which may be the seed of future collaboration. Thank you, Jose for the great talk! Reported by Gen Kurosawa

20231109
Paper of the WeekWeek 2, November 2023
Title: Constraints on the NeutronStar Structure from the Clocked XRay Burster 1RXS J180408.9$$342058 Author: Akira Dohi, Wataru Iwakiri, Nobuya Nishimura, Tsuneo Noda, Shigehiro Nagataki, Masaaki Hashimoto arXiv: http://arxiv.org/abs/2311.02853v1 Title: Thermal behavior of effective U_A(1) anomaly couplings in reflection of higher topological sectors Author: G. Fejos, A. Patkos arXiv: http://arxiv.org/abs/2311.02186v1 Title: Coupledchannel $Λ_{c}K^{+}pD_{s}$ Interaction in Flavor $ \textrm{SU}\left(3\right) $ Limit of Lattice QCD Author: Faisal Etminan, Kenji Sasaki, Takashi Inoue arXiv: http://arxiv.org/abs/2311.02569v1 Title: Operator dynamics in Lindbladian SYK: a Krylov complexity perspective Author: Budhaditya Bhattacharjee, Pratik Nandy, Tanay Pathak arXiv: http://arxiv.org/abs/2311.00753v1

20231102
Paper of the WeekWeek 1, November 2023
Title: Exploring Neutrino Mass Orderings through Supernova Neutrino Detection Author: Maria Manuela Saez Journal Reference: Universe 2023, 9, 464 doi: https://doi.org/10.3390/universe9110464 arXiv: http://arxiv.org/abs/2310.19939v1 Title: Inhomogeneous quenches as state preparation in twodimensional conformal field theories Author: Masahiro Nozaki, Kotaro Tamaoka, Mao Tian Tan arXiv: http://arxiv.org/abs/2310.19376v1 Title: The homology of moduli spaces of 4manifolds may be infinitely generated Author: Hokuto Konno arXiv: http://arxiv.org/abs/2310.18695v1

20231031
Seminar ReportDMWG Seminar by Wen Yin on September 25, 2023
However, we have to treat the production of DM carefully before giving up the possibility that DM of m~O(1)eV. Let us consider the production of scalar DM from decays of heavier fermion which was in the thermal equilibrium of the Universe and light compared to the background temperature. The evolution of the number density of the DM particle is obtained by solving the Boltzmann equation. Due to the bosonic nature of this DM, the number density at some specific momentum enhances significantly, showing an exponentially fast increase. This enhanced production stops when the inverse reaction of the DM production takes over. As a result, we have a DM distribution function that is significantly different from those predicted for thermallyproduced ones. Note that the momentum of the produced DM is relatively low, in that sense, it can be said as "cold" DM while its mass is in the "hot" DM range. Such a scenario can be realized in the context of particle physics. Model parameters are restricted by requiring to satisfy the relic abundance and the enhanced production to happen. We will see the signatures in the current Universe by observing at the infrared range searching for the signature of photon lines corresponding to the DM mass, which is a distinctive one! Reported by Nagisa Hiroshima

20231031
Seminar ReportDMWG Seminar by Simon Thor on October 24, 2023
The Standard Model of particle physics nicely describes our worlds, while we are not satisfied with this theory as there are phenomena we cannot explain exist. Dark matter (DM) is a famous example. The construction of the Standard Model is achieved by tremendous discoveries at collider experiments. It is a natural prediction that the extension of the Standard Model will be achieved with further discoveries at collider experiments. Hoping for such a scenario, several future collider experiments, such as the international linear collider (ILC), are now being planned. ILC is good at probing new physics scenarios which is related to the Higgs sector of the Standard Model. The dark neutrino model is one example that contains new dark sector particles. If the mass of the dark neutrino falls between that of the weak bosons and the Higgs, the prediction can be relatively clear: characterization of the signal can be done with three parameters in the model. Still, there are difficulties to overcome. As is usual the case, we have to find signals from data with significant background events. For example, one first makes preselection, then performs the rectangular cut (a kind of optimization), and finally tests the significance of the signal. By introducing machine learning techniques to several analysis parts the sensitivity to the model can be increased. Test using simulation data for ILC experiments at the centerofmass energy 250GeV, it is shown that the constraints on the dark neutrino model can be improved by one or two orders of magnitude. Further improvement can be achieved by introducing new ideas for the analysis, which will be investigated. By increasing the number of channels to be analyzed, the mass range of the dark neutrino to be probed can also be widened. A lot of physics has already been done with colliders, and further more is to be with new colliders and new techniques. We are boosting now! Reported by Nagisa Hiroshima

20231027
Researches & ResearchersRefining Number Theory Geometry through Inspiration from Researchers in Different Fields  Hiroyasu Miyazaki
What comes to mind when you hear the term "mathematical researcher"? Is it an image of someone shut away in a room, tirelessly conducting research? While this may be one side of a mathematician's life, discussions and communication with others can also lead to insights and problemsolving breakthroughs. Senior Research Scientist Hiroyasu Miyazaki believes that being in the interdisciplinary environment of iTHEMS has greatly expanded his perspective.

20231027
AwardTakeru Yokota received 18th Young Scientist Award
Takeru Yokota (SPDR, iTHEMS) received 18th Young Scientist Award (Theoretical Nuclear Physics) from The Physical Society of Japan for his "Construction of energy density functional with functionalrenormalizationgroup method".Congratulations, Takeru!

20231027
AwardHidetoshi Taya received 18th Young Scientist Award
Hidetoshi Taya (SPDR, iTHEMS) received 18th Young Scientist Award (Theoretical Nuclear Physics) from The Physical Society of Japan for his "Fundamental research on cooperative phenomena in perturbative and nonperturbative particle production processes under electric fields". Congratulations, Hidetoshi!

20231027
AwardSeishiro Ono received 7th Young Researcher Incentive Award
Seishiro Ono (SPDR, iTHEMS) received 7th Young Researcher Incentive Award from HighTemperature Superconducting Forum for his "Comprehensive study of symmetry and topology in superconductors". Congratulations, Seishiro!

20231026
Paper of the WeekWeek 5, October 2023
Title: NambuGoldstone modes in a lattice NambuJonaLasinio model with multi flavor symmetries Author: Yukimi Goto, Tohru Koma arXiv: http://arxiv.org/abs/2310.15922v1 Title: The extraction of higherorder radial moments of nuclear charge density from muonic atom spectroscopy Author: Hui Hui Xie, Jian Li, Haozhao Liang arXiv: http://arxiv.org/abs/2310.09546v1

20231026
Press Release"Genuine Tetraquark" Consisting of Four Quarks  Supercomputer Fugaku unravels a new particle discovered in accelerator experiment 
The international research group including Yan Lyu (former Student Trainee from Peking Univ., iTHEMS), Takumi Doi (Senior Research Scientist, iTHEMS) and Tetsuo Hatsuda (Program Director, iTHEMS) has theoretically unraveled the properties of the genuine tetraquark state Tcc, composed of four quarks. This research achievement is expected to contribute to the understanding of a fundamental question in modern physics: how quarks, the elementary particles, can combine to form new states of matter. For more details, please refer to the press release article in the related link.

20231019
Paper of the WeekWeek 4, October 2023
Title: Can we explain cosmic birefringence without a new light field beyond Standard Model? Author: Yuichiro Nakai, Ryo Namba, Ippei Obata, YuCheng Qiu, Ryo Saito arXiv: http://arxiv.org/abs/2310.09152v1 Title: The statistics and sensitivity of axion wind detection with the homogeneous precession domain of superfluid helium3 Author: Joshua W. Foster, Christina Gao, William Halperin, Yonatan Kahn, Aarav Mande, Man Nguyen, Jan SchütteEngel, John William Scott arXiv: http://arxiv.org/abs/2310.07791v1 Title: Effective Brane Field Theory with Higherform Symmetry Author: Yoshimasa Hidaka, Kiyoharu Kawana arXiv: http://arxiv.org/abs/2310.07993v1

20231013
Seminar ReportiTHEMS Biology Seminar by Theo Gibbs on October 10, 2023
A central assumption in most ecological models is that the interactions in a community operate only between pairs of species. However, two species may interactively affect the growth of a focal species. Although interactions among three or more species, called higherorder interactions, have the potential to modify our theoretical understanding of coexistence, ecologists lack clear expectations for how these interactions shape community structure. In this talk, Theo Gibbs (Ph. D, Princeton Univ.) will analyze two different sets of assumptions for how higherorder interactions impact the dynamics of competing species and show that they lead to differing outcomes. When higherorder interactions are sampled from unconstrained probability distributions, they are unlikely to generate widespread coexistence. In fact, using an analytical technique from statistical physics, he will show many — though not all — of the qualitative rules derived for pairwise interactions still apply to the higherorder case. Higherorder interactions that have specific relationships with the underlying pairwise interactions, however, can stabilize coexistence in diverse communities. He will conclude by briefly discussing ongoing experimental work that seeks to determine whether or not the dynamics of annual plant communities are structured by higherorder interactions. Reported by Keiichi Morita

20231012
Paper of the WeekWeek 3, October 2023
Title: Foliated BF theories and Multipole symmetries Author: Hiromi Ebisu, Masazumi Honda, Taiichi Nakanishi arXiv: http://arxiv.org/abs/2310.06701v1

20231012
Seminar ReportABBLiTHEMS Joint Astro Seminar by Amir Levinson on October 6, 2023
Amir initiated his seminar by presenting a detailed review of multimessenger astronomy, with a particular focus on neutrinos and their relationship with Active Galactic Nuclei (AGNs). AGNs are extraordinary astrophysical systems in which accreting black holes, situated at the centers of galaxies, generate emissions so luminous that they outshine their host galaxies. In the latter part of his presentation, Amir delved into the mechanisms responsible for neutrino production within the core of AGNs, including insights from his own research. His work has been motivated by the IceCube collaboration's recent claim of detecting highenergy neutrinos originating from the direction of NGC 1068. He highlighted the considerable challenges in theoretically reproducing the neutrino spectrum suggested in the IceCube’s observational data. A significant challenge arises when considering the energy distribution of protons accelerated in the highly magnetized core regions of Active Galactic Nuclei (AGNs). Recent particleincell (PIC) simulations have found energy distributions that are too 'hard' to successfully replicate the anticipated neutrino spectrum. He discussed one way to circumvent this problem is to consider a population of preaccelerated protons being injected into turbulent regions before they undergo acceleration processes governed by turbulence. He suggested that one way to circumvent this problem is to consider a population of preaccelerated protons that are injected into turbulent regions before undergoing acceleration processes governed by turbulence. This idea was supported by his PIC simulations, and he further discussed how this mechanism may be realized within the core regions of AGNs. Reported by Hirotaka Ito

20231006
Seminar ReportABBLiTHEMS Joint Astro Seminar by Chelsea Braun on October 6, 2023
Presented was a systematic, global study of Galactic supernova remnants (SNRs) hosting Central Compact Objects (CCOs) aimed at addressing their explosion properties and supernova progenitors. With the Chandra and XMMNewton telescopes, a spatially resolved Xray spectroscopy study is performed on seven SNRs that show evidence of shockheated ejecta. Using an algorithm, we segmented each SNR in the sample into regions of similar surface brightness. These regions were fit with one or twocomponent plasma shock model(s) in order to separate the forwardshocked interstellar medium from the reverse shockheated ejecta which peak in the Xray bands for elements including O, Ne, Mg, Si, S, Ar, Ca, and Fe. Dr. Braun and her collaborators subsequently derived the explosion properties for each SNR in the sample and found overall low explosion energies (<10^51 erg). To address their progenitor mass, they compared the measured abundances from our spectroscopic modelling to five of the most widely used explosion models and a relatively new electroncapture supernova model. Additionally, they explored degeneracy in the explosion energy and its effects on the progenitor mass estimates. However, no explosion models match all of the measured ejecta abundances for any of the SNRs in our sample. Therefore, she presented our best progenitor mass estimates and find overall low progenitor masses (<=25 solar masses) and we highlight the discrepancies between the observed data and the theoretical explosion models. Reported by Shigehiro Nagataki

20231006
Person of the WeekSelfintroduction: Yuto Yamamoto
I specialize in tropical geometry, a field of mathematics that naturally emerges when considering the limits of spaces with respect to some parameters. My primary research interest lies in calculating the limits of invariants of the spaces using tropical geometry. Despite being a relatively new field, tropical geometry has already demonstrated its applicability to other various sciences. During my time at iTHEMS, I look forward to exploring such applicational aspects of tropical geometry as well.

20231006
Press ReleaseSuccess in Calculating Cluster Occurrence Probability for New Coronavirus Infections
A research group led by Shingo Iwami (Professor, Graduate School of Science, Nagoya University / Visiting Scientist, RIKEN iTHEMS) in collaboration with the University of Oxford (UK), has achieved the world's first successful calculation of the probability of cluster occurrence due to new coronavirus infections. For more details, please visit Nagoya University's website (in Japanese) or EurekAlert! (in English) through the related links.

20231006
Person of the WeekSelfintroduction: Misako Tatsuuma
I'm Misako Tatsuuma, and I joined iTHEMS as a Research Scientist in October 2023. My research focuses on planetary formation theory. Specifically, I'm working on the formation process of planetesimals, which are kilometersized bodies like comets and asteroids, from micronsized cosmic dust grains. This process is still not fully understood and has been extensively studied through observations, explorations, experiments, and simulations. My approach involves investigating the material strengths of dust aggregates using dust grain Nbody simulations and comparing the results with explorational findings of comets and asteroids in our solar system. I got my Ph.D. in March 2022 at the University of Tokyo and subsequently began the JSPS fellow (PD) at Tokyo Institute of Technology. As for personal, I'm a mother of two and facing the ongoing challenge of balancing childcare and research.

20231005
Paper of the WeekWeek 2, October 2023
Title: The deconfinement phase transition in $Sp(2N)$ gauge theories and the density of states method Author: David Mason, Biagio Lucini, Maurizio Piai, Enrico Rinaldi, Davide Vadacchino arXiv: http://arxiv.org/abs/2310.02145v1 Title: Classification of HighOrdered Topological Nodes Towards MFBs in Twisted Bilayers Author: Fan Cui, Congcong Le, Qiang Zhang, Xianxin Wu, Jiangping Hu, ChingKai Chiu arXiv: http://arxiv.org/abs/2310.00662v1 Title: Berry's phase and quantum mechanical formulation of anomalous Hall effect Author: Kazuo Fujikawa, Koichiro Umetsu arXiv: http://arxiv.org/abs/2310.02052v1 Title: Possible inconsistency between phenomenological and theoretical determinations of charge symmetry breaking in nuclear energy density functionals Author: Tomoya Naito, Gianluca Colò, Tetsuo Hatsuda, Haozhao Liang, Xavier RocaMaza, Hiroyuki Sagawa arXiv: http://arxiv.org/abs/2309.17060v1

20231005
Person of the WeekSelfintroduction: Shinichiro Fujii
My name is Shinichiro Fujii. I was originally a nuclear theorist. After finishing my PhD at Kyushu University in 2000, I joined RIKEN as a special postdoctral researcher. After that, I had several positions including associate professor at the University of Tokyo. After a period of unemployment at the age of 40 due to the term limit, I was hired by JSTCRDS as a fellow in 2013. I conducted research and survey activities to formulate Japan's science and technology policy for 5 years. After that, I was involved in the management of large national projects related to quantum computers and quantum communications, such as JSTERATO, QLEAP and Moonshot Goal 6, at the University of Tokyo and Yokohama National University for 5 years. 23 years after beginning my career as a researcher at RIKEN, I am back to RIKEN as a coordinator in 2023. I would like to contribute to creating a better environment for researchers and enhancing the value of RIKEN.

20231004
Seminar ReportiTHEMS Biology Seminar by Yoshitomo Kikuchi on October 3, 2023
In this seminar, I hosted Dr. Kikuchi from AIST, who delivered a lecture on the symbiosis between insects and microbes. In agriculture, the development of insecticide resistance in insects is a pressing issue, and one of the contributing factors is the presence of symbiotic bacteria within insects. His seminar experimentally demonstrated that insecticideresistant bacteria residing in the soil can become symbiotic with insects by being ingested and adapting within the insect's gut. Their discovery is of significant importance for understanding various causes of insect resistance. Notably, the insects they focus on have very narrow intestinal tunnels, with bacteria either capable or incapable of passing through. Furthermore, they discovered that to traverse these narrow tunnels, bacteria engage in a unique movement called "drill motility," where they wrap their flagella around their bodies and twist while moving. This drill motility is a highly unique form of movement, and it is currently being researched in their project titled "The Reason why microbes are moving" from ecological, molecular biological, and physical perspectives. In the latter part of the seminar, advancements in the research related to this drill motility were discussed. These studies on hostmicrobe interactions based on microbial behavior have evolved into a grand interdisciplinary research effort encompassing physics, mathematics, and informatics. Throughout the seminar, discussions were held regarding the fusion of mathematical sciences with biological research, making it a highly dynamic event. Reported by Daiki Kumakura

20230928
Paper of the WeekWeek 5, September 2023
Title: A model of randomlycoupled Pauli spins Author: Masanori Hanada, Antal Jevicki, Xianlong Liu, Enrico Rinaldi, Masaki Tezuka arXiv: http://arxiv.org/abs/2309.15349v1 Title: A closer look at parameter identifiability, model selection and handling of censored data with Bayesian Inference in mathematical models of tumour growth Author: Jamie Porthiyas, Daniel Nussey, Catherine A. A. Beauchemin, Donald C. Warren, Christian Quirouette, Kathleen P. Wilkie arXiv: http://arxiv.org/abs/2309.13319v1 Title: Error estimate for regularized optimal transport problems via Bregman divergence Author: Keiichi Morikuni, Koya Sakakibara, Asuka Takatsu arXiv: http://arxiv.org/abs/2309.11666v1

20230927
Seminar ReportABBLiTHEMS Joint Astro Seminar by Arno Vanthieghem on September 8, 2023
Relativistic radiationmediated shocks (RRMS) dictate the early emission in numerous transient sources such as supernovae, low luminosity gammaray bursts, binary neutron star mergers, and tidal disruption events. These shock waves are mediated by Compton scattering and copious electronpositron pair creation. It has been pointed out that a high pair multiplicity inside the shock transition leads to a leptonbaryon velocity separation, prone to plasma instabilities. The interaction of the different species with this radiationmediated microturbulence can lead to coupling and heating that is unaccounted for by current singlefluid models. Arno presented a theoretical analysis of the hierarchy of plasma microinstabilities growing in an electronion plasma loaded with pairs and subject to a radiation force. His results are validated by particleincell simulations that probe the nonlinear regime of the instabilities and the leptonbaryon coupling in the microturbulent electromagnetic field. Based on this analysis, he derived a reduced transport equation for the particles that demonstrates anomalous coupling of the species and heating in a Joulelike process by the joined contributions of the decelerating turbulence, radiation force, and electrostatic field. Arno then discussed the effect of finite magnetization on the general dynamics and recent efforts toward a more selfconsistent description of the coupling. In general, his results suggest that radiationmediated microturbulence could have important consequences for the radiative signatures of RRMS. Reported by Shigehiro Nagataki

20230926
Seminar ReportiTHEMS Biology Seminar by Ryo Yamaguchi on June 8, 2023
During this session, Dr. Yamaguchi delivered a lecture on evolutionary ecology and its theoretical aspects. He is a researcher who has successfully discovered and quantified new biodiversity patterns through mathematical models in population genetics. In this presentation, he explained his recent research findings in a way that even beginners could easily understand. Various questions and discussions took place. Particularly noteworthy was the high compatibility of his expertise in insects and yeast with other biological fields, allowing for exchanges of ideas with various researchers. My own area of expertise lies in microbiology, specifically in bacteria. While his models primarily focus on eukaryotic organisms, direct application may be challenging, but applying his concepts is feasible. Applying these concepts is likely to yield new insights into the heterogeneity of populations in microbiology. In conclusion, this presentation provided a valuable platform for active discussions among researchers from diverse biological disciplines, making it a highly meaningful session. Reported by Daiki Kumakura

20230921
Paper of the WeekWeek 4, September 2023
Title: Dynamical chirality production in one dimension Author: Tomoya Hayata, Katsumasa Nakayama, Arata Yamamoto arXiv: http://arxiv.org/abs/2309.08820v1 Title: Chemical potential (in)dependence of hadron scatterings in the hadronic phase of QCDlike theories and its applications Author: Kotaro Murakami, Etsuko Itou, Kei Iida arXiv: http://arxiv.org/abs/2309.08143v1 Title: Zariski dense discontinuous surface groups for reductive symmetric spaces Author: Kazuki Kannaka, Takayuki Okuda, Koichi Tojo arXiv: http://arxiv.org/abs/2309.08331v1 Title: Limits to Fluctuation Dynamics Author: Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2309.07301v1 Title: Genus$g$, $n$point, $b$boundary, $c$crosscap correlation functions of twodimensional conformal field theory: Definition and general properties Author: Xun Liu arXiv: http://arxiv.org/abs/2309.07528v1

20230918
Seminar ReportQuantum Matter Seminar by Ashley Cook on September 14, 2023
In a recent online seminar for RIKEN iTHEMS' QMSG series, Dr. Ashley Cook of the Max Planck Institute for Complex Systems delved into her interesting research on topological skyrmion phases in electronic systems. The talk was centered on noninteracting electronic topological phases that feature a skyrmion in their momentumspace spin polarization. After a succinct introduction that framed the talk within the broader context of topological classification in condensed matter physics, Dr. Cook pivoted to explore quantum skyrmion structures in momentum space. She specifically discussed these structures in the context of expected spin polarization in the ground state of centrosymmetric superconductors. Intriguingly, she demonstrated that the topological protection of the skyrmion number extends to the electronic structure through a generalized bulkboundary correspondence, after accounting for nonspin degrees of freedom. This results in the formation of unique edge states that bridge one types of the energy bands (conduction bands and valence bands). Moreover, Dr. Cook emphasized that the adiabatic pumping of these edge states signifies the flow of quantum skyrmions. She suggested that this insight necessitates a reevaluation of the theoretical framework for the quantum Hall effects, which was initially conceived around point charges nearly half a century ago. Her work, therefore, not only suggests a pathway to discover new forms of topological boundary states but also calls for a more nuanced classification of topological states in electronic matter, beyond the limitations of the "tenfold way." The talk sparked a lively discussion, underscoring its significance and the excitement it generated among the participants. We extend our gratitude to Dr. Ashley Cook for her illuminating and thoughtprovoking contribution. Reported by ChingKai Chiu (iTHEMS) and Thore Posske (University of Hamburg, Germany)

20230914
Paper of the WeekWeek 3, September 2023
Title: Dynamic relationship between XRP price and correlation tensor spectra of the transaction network Author: Abhijit Chakraborty, Tetsuo Hatsuda, Yuichi Ikeda arXiv: http://arxiv.org/abs/2309.05935v1 Title: Greybody Factors Imprinted on Black Hole Ringdowns: an alternative to superposed quasinormal modes Author: Naritaka Oshita arXiv: http://arxiv.org/abs/2309.05725v1 Title: Symmetryresolved Entanglement Entropy, Spectra & Boundary Conformal Field Theory Author: Yuya Kusuki, Sara Murciano, Hirosi Ooguri, Sridip Pal arXiv: http://arxiv.org/abs/2309.03287v1

20230907
Paper of the WeekWeek 2, September 2023
Title: Efficient Simulation of Low Temperature Physics in OneDimensional Gapless Systems Author: Yuya Kusuki, Kotaro Tamaoka, Zixia Wei, Yasushi Yoneta arXiv: http://arxiv.org/abs/2309.02519v1 Title: Involutions and the ChernSimons filtration in instanton Floer homology Author: Antonio Alfieri, Irving Dai, Abhishek Mallick, Masaki Taniguchi arXiv: http://arxiv.org/abs/2309.02309v1 Title: A Semiclassical Spacetime Region with Maximum Entropy Author: Yuki Yokokura arXiv: http://arxiv.org/abs/2309.00602v1

20230905
Seminar ReportLabTheory Standing Talk #2 by Yusaku Nishimiya on September 5, 2023
At this LabTheory Standing Talks, taken place at the third floor open space, Yusaku Nishimiya explained the effect of heavyion beam on yeast. Reported by Tsukasa Tada

20230827
Hot Topic3rd Summer School of Mathematical Biology
From the 23rd to the 25th of August 2023, the 3rd Summer School of Mathematical Biology took place at Sokendai University (Hayama, Kanagawa Prefecture). It was a lecture camp organized primarily by our iTHEMS colleagues, Daiki Kumakura and Keiichi Morita. The topics included virus evolution, immune response, coexistence theories in biology and rapid evolution, human migration and its processes, optimization strategies in marine organism reproduction, and modeling biological metabolism. At the summer school, Tetsuo Hatsuda (iTHEMS Director) also participated as an attendee. In the end, there was a fruitful event, including an introduction to iTHEMS. The summer school will be held again next year.

20230825
Seminar ReportExploring 2D Quantum Spacetime Based on Causal Dynamical Triangulations by Yuki Sato on August 21, 2023
The fourth set of intensive lectures organised by the iTHEMS Quantum Gravity Gatherings study group has now concluded. Approximately 15 participants joined this three day event in which we were given a comprehensive overview of the causal dynamical triangulations (CDT) approach to 2D quantum spacetime. Leading affairs was Dr Yuki Sato of the National Institute of Technology, Tokuyama College, who presented in a tightly organised and very pedagogical manner. Following some brief motivations for the CDT approach to quantum gravity and a summary of the numerical understanding of the theory in 4D, Satosan began with an overview of discrete geometry in Lorentzian spaces and used this to introduce Lorentzian Regge calculus. The fundamental idea here is to realise curvature as a conical defect at certain codimension 2 regions of piecewiseflat manifolds. We concluded the first day by using this to construct the Lorentzian EinsteinRegge action in arbitrary dimension before specialising to the 2D case. We began the second day by explicitly quantising this 2D action and then proceeded to take its continuum limit, allowing for the deduction of the quantum Hamiltonian of the theory. We then briefly covered the formalism of 2D projectable Hořava–Lifshitz (PHL) gravity and demonstrated the equivalence of this theory to 2D CDT by showing that PHL gravity is described by the same Hamiltonian as in the CDT case. On the third day we learnt about a generalisation of the 2D CDT model allowing for topology change to occur, employing ideas from string field theory in the process; we studied a dual matrix model representation of the theory and derived an effective quantum Hamiltonian including the contribution of such wormhole configurations. Finally we saw how topology change in 2D generalised CDT could be realised in terms of stochastic timedependent fluctuations of the cosmological constant in line with the socalled Coleman mechanism. In addition to the scientific activities above we had a number of short talks on the first and second days of the event by participants as well as a banquet on the first day where we were joined by several iTHEMS members. The intimate nature of the event lead to the active participation of attendees and overall a very lively and productive learning environment. Reported by Christy Koji Kelly

20230824
Paper of the WeekWeek 4, August 2023
Title: Universality in quasinormal modes of neutron stars with quarkhadron crossover Author: Hajime Sotani, Toru Kojo arXiv: http://arxiv.org/abs/2308.11494v1 Title: KramersKrönig approach to the electric permittivity of the vacuum in a strong constant electric field Author: Hidetoshi Taya, Charlie Ironside arXiv: http://arxiv.org/abs/2308.11248v1 Title: de Sitter space is sometimes not empty Author: Vijay Balasubramanian, Yasunori Nomura, Tomonori Ugajin arXiv: http://arxiv.org/abs/2308.09748v1 Title: Plant GARDEN: a portal website for crosssearching between different types of genomic and genetic resources in a wide variety of plant species Author: Hisako Ichihara, Manabu Yamada, Mitsuyo Kohara, Hideki Hirakawa, Andrea Ghelfi, Takuro Tamura, Akihiro Nakaya, Yasukazu Nakamura, Sachiko Shirasawa, Samatchaya Yamashita, Yosuke Toda, Daijiro Harada, Tsunakazu Fujishiro, Akiko Komaki, Jeffrey A. Fawcett, Eiji Sugihara, Satoshi Tabata, Sachiko N. Isobe Journal Reference: BMC Plant Biology 23, 391 (2023) doi: https://doi.org/10.1186/s12870023043928 Title: Genome sequencing reveals the genetic architecture of heterostyly and domestication history of common buckwheat Author: Jeffrey A. Fawcett, Ryoma Takeshima, Shinji Kikuchi, Euki Yazaki, Tomoyuki KatsubeTanaka, Yumei Dong, Meifang Li, Harriet V. Hunt, Martin K. Jones, Diane L. Lister, Takanori Ohsako, Eri OgisoTanaka, Kenichiro Fujii, Takashi Hara, Katsuhiro Matsui, Nobuyuki Mizuno, Kazusa Nishimura, Tetsuya Nakazaki, Hiroki Saito, Naoko Takeuchi, Mariko Ueno, Daiki Matsumoto, Miyu Norizuki, Kenta Shirasawa, Chengyun Li, Hideki Hirakawa, Tatsuya Ota, Yasuo Yasui Journal Reference: Nature Plants volume 9, pages 1236–1251 (2023) doi: https://doi.org/10.1038/s41477023014741

20230823
Press ReleaseDeciphering the Buckwheat Genome  HighPrecision Genome Sequence Illuminates the Past and Future of Buckwheat 
As the world population is expected to reach 9.7 billion by 2050, the dependence on the three major cereals  rice, wheat, and corn  is becoming a concern. In response, interest in "orphan crops" is increasing, which have high value as food but whose research has lagged, leaving their potential untapped. Determining the genomes of orphan crops using nextgeneration sequencing technology is expected to promote their efficient breeding and contribute to the achievement of SDGs such as eradicating hunger and improving nutrition. An international collaborative research group (including Jeffrey Fawcett, iTHEMS) deciphered the genome sequence of buckwheat, an orphan crop cultivated in Eurasia that is used for making soba noodles in Japan, at the chromosomal level with high precision, revealing the evolution of the buckwheat genome and the origin of cultivated buckwheat. Moreover, they modified the predicted genes using methods that do not rely on genome editing technology. As a result, they successfully developed a glutinous buckwheat and a new selfpollinating buckwheat that did not previously exist. The breeding methods used in this study are expected to contribute to the improvement of a wide variety of orphan crops in which genome editing technology cannot be used. For more information, please see the Kyoto University press release article at the related links.

20230817
Paper of the WeekWeek 3, August 2023
Title: Deconfinement transition in the revolving bag model Author: Kazuya Mameda, Keiya Takizawa arXiv: http://arxiv.org/abs/2308.07310v1 Title: Universality of Effective Central Charge in Interface CFTs Author: Andreas Karch, Yuya Kusuki, Hirosi Ooguri, HaoYu Sun, Mianqi Wang arXiv: http://arxiv.org/abs/2308.05436v1

20230817
AwardYixin Guo received two awards for his presentation
Yixin Guo (iTHEMS JRA/Univ. Tokyo) received two awards for his presentation on Aug. 10 at the A3F Summer School 2023.

20230816
Seminar Report3rd QGG Intensive Lectures: Spinfoam path integrals for Quantum Gravity by Etera Livine on July 26, 2023
The 3rd Intensive Lecture by iTHEMS’ Quantum Gravity Gatherings concluded with resounding success. Around 30 enthusiasts, including students, junior and senior researchers from various disciplines, convened at the RIKEN Wako Campus to learn and discuss spinfoam quantum gravity. Prof. Etera Livine from ENS Lyon, our distinguished lecturer this time, delivered a fantastic 3day lecture about the spinfoam approach to quantum gravity (QG). He began with a wonderful introduction explaining why physicists have long sought the theory of quantum gravity: the ultimate theory that unifies physics at both macroscopic and subatomic scales. Prof. Livine highlighted various existing candidates for quantum gravity theory and forged connections among these diverse approaches. Regarding the main topic, he started with the basics of loop quantum gravity and clearly explained the origin of the fundamental discreteness of spacetime. In the latter half of his lecture, he detailed how to construct the spinfoam path integral for QG in 3D before moving on to the 4D case. He concluded his lecture by discussing the limitations of this approach and outlining future directions. Throughout his lecture, he consistently elaborated on the mathematical similarities between these QG approaches and other areas of physics, such as condensed matter physics. This allowed the audience to grasp the current advancements in the field, recognizing how their areas of expertise, seemingly distant from quantum gravity, could intricately interlace with it. This event presented a great opportunity for fostering interdisciplinary research, as it brought together people with various interests, including physicists working on highenergy physics, gravity, cosmology, and condensed matter systems, as well as pure mathematicians. Everyone exhibited keen enthusiasm for quantum gravity, creating an atmosphere of unity and togetherness that permeated the room. Many interesting questions were posed during the lecture, and participants enthusiastically engaged in discussions during coffee breaks. Some of them also shared their stories and work during the short talk sessions, and everyone enjoyed the banquet on the second day. Overall, this event provided a relaxed and active platform for learning, offering an exceptional opportunity to strengthen connections and friendships among participants, particularly those in the early stages of their research careers. Reported by Puttarak Jaiakson

20230811
Seminar ReportHigher Algebra in Geometry by Hiro Lee Tanaka on July 31, 2023
8 days of introductory lectures on Higher Algebra (infinity categories) were given by Dr. Hiro Lee Tanaka (Texas State University). Recent developments on infinitycategory theory and their applications have received attraction from various areas of mathematics, including geometric topology, symplectic geometry, and algebraic geometry. The lectures were targeted to students and researchers interested in applications of infinitycategorical tools. The first day was devoted to nonspecialists, where Dr. Tanaka introduced the concept of associativity and homotopies, and explained how they naturally lead us to the ideas of infinitycategories. From the second day, Dr. Tanaka introduced the basic concepts of infinitycagetories together with familiar examples. In the second week, some of the works of Dr. Tanaka were given as applications of the ideas of inifitycategories. His aim was to show us that these concepts are not mere abstractions, but are accessible and usefully applicable to concrete questions of geometry. The participants also shared their own works and interests after the lectures, and lively discussions took place. Reported by Taketo Sano

20230810
AwardNagisa Hiroshima received "Toyama Daiichi Bank Scholarship Foundation Award"
Nagisa Hiroshima (Toyama Univ. and iTHEMS Visiting Scientist) received "Toyama Daiichi Bank Scholarship Foundation Award (Incentive Award)". The citation for the award is "Theoretical research on dark matter using astrophysical approach". The award ceremony was held on July 7, 2023 at Toyama Daiichi Bank Head Office. The certificate and catalog of research grants were handed over to Nagisa by the Vice Governor of Toyama Prefecture. Congratulations, Nagisa!

20230810
Paper of the WeekWeek 2, August 2023
Title: Mediuminduced bosonic clusters in a BoseFermi mixture: Towards simulating cluster formations in neutronrich matter Author: Yixin Guo, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2308.04738v1 Title: Onedimensional spinless fermions with attractive two and threebody forces Author: Yixin Guo, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2308.04737v1 Title: Activityinduced ferromagnetism in onedimensional quantum manybody systems Author: Kazuaki Takasan, Kyosuke Adachi, Kyogo Kawaguchi arXiv: http://arxiv.org/abs/2308.04382v1 Title: Universal entanglement signatures of interface conformal field theories Author: Qicheng Tang, Zixia Wei, Yin Tang, Xueda Wen, W. Zhu arXiv: http://arxiv.org/abs/2308.03646v1 Title: On the Scottish Book Problem 155 by Mazur and Sternbach Author: Michiya Mori arXiv: http://arxiv.org/abs/2308.03339v1 Title: On the shape of correlation matrices for projections and unitaries Author: Michiya Mori arXiv: http://arxiv.org/abs/2308.03345v1 Title: Is the Coleman de Luccia action minimum?: AdS/CFT approach Author: Naritaka Oshita, Yutaro Shoji, Masahide Yamaguchi arXiv: http://arxiv.org/abs/2308.02159v1

20230803
Paper of the WeekWeek 1, August 2023
Title: Calculating compositeparticle spectra in Hamiltonian formalism and demonstration in 2flavor QED$_{1+1\text{d}}$ Author: Etsuko Itou, Akira Matsumoto, Yuya Tanizaki arXiv: http://arxiv.org/abs/2307.16655v1 Title: Two dimensional lattice with an imaginary magnetic field Author: Tomoki Ozawa, Tomoya Hayata arXiv: http://arxiv.org/abs/2307.14635v1

20230802
Person of the WeekSelfintroduction: Yuta Sekino (2023)
I am Yuta Sekino. After finishing my Ph. D at Tokyo Institute of Technology in 2019, I worked in RIKEN as a JSPS Postdoctoral Fellow (201921) and Postdoctoral Researcher in ABBL (202123). During 20212023, I also belonged to iTHEMS as a concurrent member. In July 2023, I officially joined iTHEMS as a Postdoctoral Researcher associated with RIKEN Quantum. I am a theoretical condensedmatter physicist mainly working on ultracold atomic systems. My main research interest is superfluidity, superconductivity, and spin transport. Because these phenomena have been widely discussed not only in condensedmatter physics but also in nuclear physics and astrophysics, I would like to collaborate with iTHEMS researchers working in these fields. As a member of RIKEN Quantum, I also would like to apply quantum computational methods to nonequilibrium phenomena such as postquench dynamics in quantum spin systems. Because quantum computing would have the potential to tackle unsolved problems in every field of science, I would be happy to have interdisciplinary discussions in RIKEN Quantum. At iTHEMS, I hope to broaden my research horizon through discussions with researchers in various fields.
161 news in 2023