News
217 news in 2022
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2022-12-29
Paper of the WeekWeek 5, December 2022
Title: Bouncing Cosmology in VCDM Author: Alexander Ganz, Paul Martens, Shinji Mukohyama, Ryo Namba arXiv: http://arxiv.org/abs/2212.13561v1 Title: Scalar, fermionic and supersymmetric field theories with subsystem symmetries in d+1 dimensions Author: Masazumi Honda, Taiichi Nakanishi arXiv: http://arxiv.org/abs/2212.13006v1 Title: Evidence of a p-$φ$ bound state Author: Emma Chizzali, Yuki Kamiya, Raffaele Del Grande, Takumi Doi, Laura Fabbietti, Tetsuo Hatsuda, Yan Lyu arXiv: http://arxiv.org/abs/2212.12690v1 Title: Peaky Production of Light Dark Photon Dark Matter Author: Yuichiro Nakai, Ryo Namba, Ippei Obata arXiv: http://arxiv.org/abs/2212.11516v1 Title: Non-Hermitian topological Fermi superfluid near the $p$-wave unitary limit Author: Hiroyuki Tajima, Yuta Sekino, Daisuke Inotani, Akira Dohi, Shigehiro Nagataki, Tomoya Hayata arXiv: http://arxiv.org/abs/2212.11633v1
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2022-12-27
Hot Topic
Ryosuke Iritani wrote an essay for The Big Issue Japan 445
Ryosuke Iritani (Research Scientist, iTHEMS) wrote an essay for The Big Issue Japan, and the latest volume (vol 445) is just published on 15th December. The Big Issue is a magazine dedicated to supporting people in difficult circumstances and helping them achieve self-reliance. Each issue costs 450 yen, out of which 230 yen is the direct income of the street sales staff. Ryosuke's comment: The essay is about my “third place,” a place separated from home and workplace for me. I hope as many people as possible take it a read and support the people!
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2022-12-22
Paper of the WeekWeek 4, December 2022
Title: Strong Lensing of High-Energy Neutrinos Author: Yoon Chan Taak, Tommaso Treu, Yoshiyuki Inoue, Alexander Kusenko arXiv: http://arxiv.org/abs/2212.08793v1 Title: Species interactions and diversity: a unified framework using Hill numbers Author: William Godsoe, Rua Murray, Ryosuke Iritani Journal Reference: Oikos e09282 (2022) doi: https://doi.org/10.1111/oik.09282 Title: Jaccard dissimilarity in stochastic community models based on the species-independence assumption Author: Ryosuke Iritani, Vicente Luis Jimenez Ontiveros, David Alonso, Jose A Capitan, William Godsoe, Shinichi Tatsumi doi: https://doi.org/10.1101/2022.12.13.520233 Title: Non-trivial band topology and orbital-selective electronic nematicity in a new titanium-based kagome superconductor Author: Yong Hu, Congcong Le, Zhen Zhao, Junzhang Ma, Nicholas C. Plumb, Milan Radovic, Andreas P. Schnyder, Xianxin Wu, Hui Chen, Xiaoli Dong, Jiangping Hu, Haitao Yang, Hong-Jun Gao, Ming Shi arXiv: http://arxiv.org/abs/2212.07958v1
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2022-12-20
Seminar Report
DMWG Seminar by Dr. Maria Manuela Saez on December 19, 2022
Please enter the seminar report here!There are many ongoing experiments searching for direct scattering between DM and nuclei all over the world. Of course, the material, location, and detailed setups are different among projects. One of them, the DAMA/LIBRA collaboration has long been reported for the continuous detection of the annual modulation of signals which should be attributed to DM interactions. However, the reports are in tension with all other experiments. In order for testing the origin of the reported signals, we need further investigations with independent experiments. ANDES (Agua Negra Deep Experiment Site) provides us with such an opportunity. The experiment is planned to be built deep underground in the Andes Mountains at the border between Argentina and Chile. It should prove not only the DM interactions, but also various neutrino physics, nuclear astrophysics, and biological topics. The One important feature of the experiment is that it is built in the Southern hemisphere and close to the equator compared to other experiments. We can predict a higher amplitude of the annual modulation signals corresponding to DM interactions with these setups. Also, there are no nearby nuclear power plants hence we can expect a lower neutrino background which means better sensitivity. On the other hand, we might have to be careful about the geo-neutrino background at a lower energy regime. The project is now under construction and investigating the best target materials and realistic equipment. It should start operations in not the far future. Stay tuned for various new insights! Reported by Nagisa Hiroshima
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2022-12-20
Seminar Report
Information Theory SG Seminar by Mr. Kohei Yoshimura on December 16, 2022
On December 16th, Mr. Yoshimura gave us a talk about the decomposition of entropy production in stochastic and chemical systems. In the introductory part, he explained the two aspects of entropy production, nonstationarity and breaking of the detailed balance, as well as the strategy to decompose it. He first introduced important concepts such as detailed balance and cycle using an example of a simple Markov jump process. He then generalized the concepts to nonlinear kinetics including chemical reaction network systems. Lastly, he explained how we can decompose entropy production into excess and housekeeping parts, providing explicit simulation results. We are very grateful to him for the well-organized presentation! Reported by Kyosuke Adachi
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2022-12-15
Paper of the WeekWeek 3, December 2022
Title: On Quantum Information Before the Page Time Author: Jonah Kudler-Flam, Yuya Kusuki arXiv: http://arxiv.org/abs/2212.06839v1 Title: Morphological and anatomical analyses clarify the species definition of Ceratozamia latifolia Miq. (Zamiaceae) and lead to the description of a new species: Ceratozamia reesii Author: Andrew P. Vovides, Miguel Angel Pérez-Farrera, María Magdalena Salinas-Rodríguez, Sonia Galicia, Pedro Díaz-Jiménez, Michael Calonje, José Said Gutiérrez-Ortega Journal Reference: Phytotaxa doi: https://doi.org/10.11646/phytotaxa.575.3.2 Title: Morphological variation between the two species of the palm genus Gaussia (Arecaceae) from Mesoamerica Author: Nancy Gabriela Santos Hernández, Miguel Angel Pérez-Farrera, Luis E. Eguiarte, Andrew P. Vovides, José Said Gutiérrez-Ortega Journal Reference: Nordic Journal of Botany doi: https://doi.org/10.1111/njb.03770 Title: Numerical analysis for the Plateau problem by the method of fundamental solutions Author: Koya Sakakibara, Yuuki Shimizu arXiv: http://arxiv.org/abs/2212.06508v1 Title: MeV Gamma-Ray Source Contribution to the Inner Galactic Diffuse Emission Author: Naomi Tsuji, Yoshiyuki Inoue, Hiroki Yoneda, Reshmi Mukherjee, Hirokazu Odaka arXiv: http://arxiv.org/abs/2212.05713v1 Title: Attention in a family of Boltzmann machines emerging from modern Hopfield networks Author: Toshihiro Ota, Ryo Karakida arXiv: http://arxiv.org/abs/2212.04692v1
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2022-12-12
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Ryo Higuchi on November 4, 2022
Telescope Array (TA) and Auger experiments reported anisotropies in the arrival direction of ultra-high-energy cosmic rays (UHECRs). In the current correlation studies between UHECRs and source candidates, the Auger experiment reported a correlation between the flux model of assumed sources and UHECR events and suggested a 10% contribution of starburst galaxies (SBGs) to the anisotropy of UHECRs. However, they do not consider the effect of coherent deflection by the galactic magnetic field (GMF), and they should significantly affect the results of the correlation studies. In this talk, Dr. Ryo Higuchi introduced a current study of UHECR anisotropy and the effect of GMF on them. Reported by Shigehiro Nagataki
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2022-12-12
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Hiroki Nagakura on December 9, 2022
Neutrinos are the most mysterious and elusive particles in the standard model of particle physics. They play important roles in core-collapse supernovae and binary neutron star mergers as driving mass-ejection, synthesizing heavy elements including r-process nuclei, and neutrino signals from these sources. This exhibits the importance of accurate modeling of neutrino radiation field in these phenomena, which will be used to connect neutrino physics to multi-messenger astronomy. It has recently been suggested that neutrino-flavor conversion (or neutrino-oscillation) can ubiquitously occur in these astrophysical environments, exhibiting the requirement of quantum kinetic treatments in the modeling of neutrino transport. In this seminar, Dr. Hiroki Nagakura gave an overview of the quantum kinetics neutrino transport and then introduced its recent progress, paying a special attention to the connection to astrophysics. Dr. Hiroki Nagakura also presented the latest results of our numerical simulations of collective neutrino oscillations, which can be properly accounted for only by quantum kinetic framework. Reported by Shigehiro Nagataki
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2022-12-08
Paper of the WeekWeek 2, December 2022
Title: The density of state method for first-order phase transitions in Yang-Mills theories Author: David Mason, Biagio Lucini, Maurizio Piai, Enrico Rinaldi, Davide Vadacchino arXiv: http://arxiv.org/abs/2212.01074v1
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2022-12-05
Seminar Report
iTHEMS Math Seminar by Dr. Yosuke Matsuzawa on November 11, 2022
On November 11, there was a math seminar by professor Matsuzawa. He gave an introductory talk on the arithmetic dynamical system. He started from simple and interesting examples to some conjectures. Reported by Keita Mikami
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2022-12-05
Seminar ReportMath-Phys Seminar by Dr. Christy Koji Kelly on October 14, 2022
On October 14, there was a joint seminar by Christy Koji Kelly. He gave an introductory talk on the rough geometry. Reported by Keita Mikami
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2022-12-05
Seminar ReportiTHEMS Math Seminar by Dr. Yusuke Aikawa on November 18, 2022
On November 18th, Yusuke Aikawa, from Information Technology R&D Center, Mitsubishi Electric Corporation, gave a talk in Math Seminar. In the first part of the talk, he made a general introduction to the public key cryptography and its historical development. In particular, he explained that a large-scale quantum computer can break today’s public key security systems. In the second part, he explained the recent attempts to create public key systems which are not easily breakable by quantum computers (so called post-quantum cryptography), with an emphasis on the methods which use elliptic curves. An elliptic curve is an algebraic curve which admits a group structure, and one can form a cryptography by using this group structure. The speaker also explained his recent joint work on a generalized methods which uses abelian varieties, which are higher dimensional algebraic varieties admitting group structure. Reported by Hiroyasu Miyazaki
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2022-12-05
Hot Topic
Four Perspectives on Neutron Stars, Pulsars, and Magnetars
The recent work [1] on X-ray bursts from the neutron stars led by our colleague, Akira Dohi (Visiting Scientist, iTHEMS), was featured in the article "Four Perspectives on Neutron Stars, Pulsars, and Magnetars" appeared in Research highlights from the Journals of the American Astronomical Society (see related link below).
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2022-12-02
Press Release
Universal Force Appearing in Quantum Fluids at Cryogenic Temperatures - Intermolecular Force in Atomic Superfluids Guided by Quantum Fluctuation
The concept of "forces acting between materials," as exemplified by the universal law of gravitation, has continued to occupy an important position in physics. An international research group including Masaru Hongo (Assistant Professor, Faculty of Science, Niigata University / Visiting Scientist, RIKEN iTHEMS) and Keisuke Fujii (Postdoctoral Researcher, University Heidelberg, Germany) have revealed from theoretical calculations that the same intermolecular force known as van der Waals force acts between particles floating in a quantum fluid at cryogenic temperatures over long distances. Atomic groups cooled to near absolute zero (several tens of nano-Kelvin) by laser technology have attracted attention in recent years as a system in which quantum states can be controlled with high precision, and they are an ideal stage for investigating forces in the microscopic world. This research has newly revealed that a universal long-range force due to quantum fluctuation acts on impurity particles in atomic superfluids realized at cryogenic temperatures. For more details, please visit Niigata University's website from the related link below.
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2022-12-01
Paper of the WeekWeek 1, December 2022
Title: A bias-free cosmological analysis with quasars alleviating $H_0$ tension Author: Aleksander Łukasz Lenart, Giada Bargiacchi, Maria Giovanna Dainotti, Shigehiro Nagataki, Salvatore Capozziello arXiv: http://arxiv.org/abs/2211.10785v2 Title: Toward nuclear physics from lattice QCD on quantum computers Author: Arata Yamamoto, Takumi Doi arXiv: http://arxiv.org/abs/2211.14550v1 Title: Quasiparticles of Decoherence Processes in Open Quantum Many-Body Systems: Incoherentons Author: Taiki Haga, Masaya Nakagawa, Ryusuke Hamazaki, Masahito Ueda arXiv: http://arxiv.org/abs/2211.14991v1 Title: Two Dimensional Isometric Tensor Networks on an Infinite Strip Author: Yantao Wu, Sajant Anand, Sheng-Hsuan Lin, Frank Pollmann, Michael P. Zaletel arXiv: http://arxiv.org/abs/2211.14337v1 Title: Density-Induced Hadron-Quark Crossover via the Formation of Cooper Triples Author: Hiroyuki Tajima, Shoichiro Tsutsui, Takahiro M. Doi, Kei Iida arXiv: http://arxiv.org/abs/2211.14194v1 Title: Measurement of hadron masses in 2-color finite density QCD Author: Kotaro Murakami, Daiki Suenaga, Kei Iida, Etsuko Itou arXiv: http://arxiv.org/abs/2211.13472v1
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2022-11-24
Seminar Report
iTHEMS Biology Seminar by Prof. Zhichao (Chichau) Miao on November 24, 2022
In this week’s biology seminar, we have invited Prof. Zhichao Miao (Guangzhou Laboratory, China) to tell us about “RNA-Puzzles - the evaluation and automation of RNA 3D structure”. He introduced the development history and current situation of the RNA 3D structure prediction problem. With agreement from crystallographers, the RNA structures are predicted by various groups before the publication of the crystal structures. Systematic protocols for comparing models and crystal structures are described and analyzed. The technic is becoming routine and accurate. However, we are surprised that even with the great success of AlphaFold for protein structure prediction, the lack of information of RNA structure is still holding back the use of advanced supervised machine learning technics. The RNA-Puzzles project is working hard to open the great possibilities in this task. He also presented the results of predicting the viral RNA structures, including the SARS-CoV-2. We are looking forward to see the further development. In the seminar, we had many insightful questions and discussions. We are very thankful for Prof. Miao’s talk and this great communication opportunity. Reported by Yingying Xu
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2022-11-24
Paper of the WeekWeek 4, November 2022
Title: Index theory of chiral unitaries and split-step quantum walks Author: Chris Bourne arXiv: http://arxiv.org/abs/2211.10601v1 Title: Emergent higher-form symmetry in Higgs phases with superfluidity Author: Yoshimasa Hidaka, Dan Kondo arXiv: http://arxiv.org/abs/2210.11492v1 Title: Entanglement Generation and Decoherence in a Two-Qubit System Mediated by Relativistic Quantum Field Author: Yoshimasa Hidaka, Satoshi Iso, Kengo Shimada arXiv: http://arxiv.org/abs/2211.09441v1 Title: Quantum Metrology Protected by Hilbert Space Fragmentation Author: Atsuki Yoshinaga, Yuichiro Matsuzaki, Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2211.09567v1
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2022-11-17
Paper of the WeekWeek 3, November 2022
Title: Carrollian hydrodynamics and symplectic structure on stretched horizons Author: Laurent Freidel, Puttarak Jai-akson arXiv: http://arxiv.org/abs/2211.06415v1
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2022-11-10
Paper of the WeekWeek 2, November 2022
Title: Entanglement Dynamics of the Non-Unitary Holographic Channel Author: Kanato Goto, Masahiro Nozaki, Kotaro Tamaoka, Mao Tian Tan arXiv: http://arxiv.org/abs/2211.03944v1 Title: Projecting XRP price burst by correlation tensor spectra of transaction networks Author: Abhijit Chakraborty, Tetsuo Hatsuda, Yuichi Ikeda arXiv: http://arxiv.org/abs/2211.03002v1 Title: Homological instability for moduli spaces of smooth 4-manifolds Author: Hokuto Konno, Jianfeng Lin arXiv: http://arxiv.org/abs/2211.03043v1 Title: A family of slice-torus invariants from the divisibility of reduced Lee classes Author: Taketo Sano, Kouki Sato arXiv: http://arxiv.org/abs/2211.02494v1 Title: Probing hadron mass spectrum in dense two-color QCD with linear sigma model Author: Daiki Suenaga, Kotaro Murakami, Etsuko Itou, Kei Iida arXiv: http://arxiv.org/abs/2211.01789v1
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2022-11-10
Hot Topic
Naritaka Oshita presented his talk at the 12th Koshien of Science (Oita tournament) on November 3, 2022
The 12th Koshien of Science (Oita tournament), a scientific competition for high school students in Oita prefecture, was held on 3rd November 2022 at Oita city. Naritaka Oshita from iTHEMS presented his talk on “Black Holes Veiled in Mystery” after the competition. More than 200 high school students from Oita prefecture attended. Oshita talked about the history of science, recent progress, and remaining mysteries of black holes. A student asked a unique question “What if we fall into a black hole? Can our consciousness be recovered from the hole?”. Another student asked, “How can it be possible to detect the signal from a ringing black hole?”. The audience enjoyed the stimulating talk and questions from the students. During the competition, Oshita and an iTHEMS assistant Tomoko Iwanami observed the competition, where some students built their toy cars in each group and competed in a race.
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2022-11-07
Seminar Report
DMWG Seminar by Dr. Oscar Macias on October 28, 2022
Dark matter (DM) is only a part of the mysterious phenomena in our Universe. As our exploration of the Universe proceeds, we frequently meet new mysteries. The Fermi bubble is such an example. Fermi-LAT founds extended gamma-ray emissions in the vertical direction from the Galactic Center and the origin is still unknown. Observations in other wavelengths could give some hints about its interpretation. The Saggitarius stellar stream, which is believed to be a dwarf spheroidal galaxy (dSph) being disrupted, seems to overlap with the Fermi Bubble region. Old star populations including milli-second pulsars, which are famous gamma-ray emitters, can be expected in dSphs. However, the spectrum of milli-second pulsars is different from that of the Fermi Bubble and the interpretation cannot be possible in a straightforward way. Another key ingredient for this consideration is the gas component of the Saggitarius stream. In such environments, inverse Compton emission should contribute to the high-energy regime and gamma-ray emission should be interpreted with two components. The prediction of this two-component model fairly matches the observed properties of the Fermi Bubble. This fact, at this stage, leads to another hint to DM study. Currently, one of the tightest constraints of the DM annihilation cross-section is obtained from gamma-ray observations of dSphs. When we consider such investigations, usually it is assumed that astrophysical gamma-rays are subtle enough. However, regarding the fact that the tidally disrupted dSph of Saggitarius emits gamma rays from interactions of baryonic components, we must be careful about the target selection of dSphs for future observations. It is suggested in the talk that the ordering of the promising dSphs for the future gamma-ray search of DM could be different. Interaction between visible and invisible sectors in our Universe always brings us fruitful insights. We will meet further indications in this era by boosting astrophysical studies. Reported by Nagisa Hiroshima
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2022-11-04
Hot Topic
Science Agora 2022 is held November 4-6, 2022
Science Agora 2022 is held online and in person in the period Nov. 4-6, 2022. There will be many fun sessions that you can join in person or online. There are English sessions too. RIKEN will have a session "Envisioning Futures: Navigating the research landscape with senior women researchers" in which Tetsuo Hatsuda from iTHEMS is one of the speakers. Enjoy !
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2022-11-03
Paper of the WeekWeek 1, November 2022
Title: Nuclei in Core-Collapse Supernovae Engine Author: Shun Furusawa, Hiroki Nagakura arXiv: http://arxiv.org/abs/2211.01050v1
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2022-11-02
Person of the Week
Self-introduction: Puttarak Jai-akson
My name is Puttarak Jai-akson. I hail from Thailand and I obtained my bachelor’s degree there. I then moved to Canada to join the PSI program and completed my PhD at Perimeter Institute. I joined iTHEMS in November 2022 as a postdoctoral researcher and I have been very excited to learn, share, and cultivate new ideas with fellow researchers in this interdisciplinary environment. My research mainly focuses on theoretical aspects of gravity, leaning especially towards the theme of black holes, holography, and quantum gravity. I am interested in the idea of quasi-local holography, centering around the study of gravity in finite regions of spacetime where a wealth of fascinating mathematical structures and physics is unfolded. One topic which I have been currently pursued is the underlying correspondence between gravitational physics near finite null boundaries (such as black hole horizons) and Carrollian hydrodynamics, an unusual type of fluid dynamics living at the opposite corner to the conventional Navier-Stokes fluid dynamics. This correspondence will certainly shed light on the better understanding of black holes and their thermodynamical properties. I also believe that the connection between gravity and hydrodynamics will open a new route for the grand quest to quantize gravity.
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2022-11-02
Person of the Week
Self-introduction: Maria Manuela Saez
Hola!, This is Maria Manuela Saez, an Argentinian astronomer and a new RIKEN - Berkeley postdoctoral fellow. I'm interested in astrophysics, and in particular, my research focuses on the study of core-collapse supernovae and the role that neutrinos play in these astrophysical environments. Core-collapse supernovae are the final evolutionary stage of massive stars and represent a long-awaited observation target for neutrino telescopes. To explain these events, one needs an interdisciplinary field of research that combines nuclear physics, particle physics, astrophysics and numerical simulations. Studying the signals that the supernovae' neutrino fluxes leave in the detectors, with an appropriate neutrino flavor discrimination, is possible to infer properties of the physics of the neutrinos involved and to study scenarios with non-standard neutrino properties. The structure of the neutrino mass spectrum and lepton mixing is imprinted into the detected signal. My goal is to contribute, from a theoretical perspective to the definition of strategies for detecting and studying neutrinos in large underground neutrino and dark matter detectors. I'm looking forward to discussing and collaborating with iTHEMS people.
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2022-11-02
Person of the Week
Self-introduction: Ermal Rrapaj
Hi, my name is Ermal Rrapaj, and I am a new RIKEN-Berkeley fellow. My research centers on the intersection of quantum many body physics and astrophysics. The general focus is on how particle interactions affect the properties of extreme environments such as supernovae and neutron stars and how they relate to earth experiments. The main research topics include properties of nuclei that could be tested in future experiments, neutrino nucleon matter interactions, transport properties of neutron stars, supernovae equation of state, and astrophysical implications from BSM particles. In recent years Ermal has been exploring how new technologies such as machine learning (neural networks) and quantum computing can aid in these research venues.
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2022-11-01
Person of the Week
Self-introduction: Thomas Hitchcock
Hi, I’m Thomas Hitchcock. I grew up in the UK, studying Genetics and Systems Biology at the University of Cambridge, before moving up to the University of St Andrews to do my PhD in Evolutionary Genetics, and have now joined iTHEMS as an SPDR. I’m interested in why organisms appear the way they do, and how we can use evolutionary theory to better understand this. In practice, I’ve study two main flavours of problem, (1) when and why do organisms (and genes) come into conflict with one another, and (2) how are organisms (and genes) expected to weight different fitness trade-offs. To tackle these problems, I use a mix of population genetics and evolutionary game theory, and focus mainly on unusual genetic systems, life histories, and ecologies, which I hope might prove particularly clear tests of theory. I’m excited to discuss and learn from the wide variety of researchers at iTHEMS, and hopefully incorporate some new mathematical tools and frameworks into ecology and evolution.
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2022-10-28
Hot Topic
Listening to Equation-of-State Changes
The collaborative work on the quark matter and gravitational wave [1] led by our iTHEMS colleague, Yongjia Huang, together with Shigehiro Nagataki, Tetsuo Hatsuda, Kentaro Takami, Hajime Soltani and others, was featured in the Physics Magazine published by the American Physical Society with the title "Listening to Equation-of-State Changes" (see related links below). See how the general relativistic simulations of the postmerger gravitational waves from coalescing neutron stars could allow us to hear the phase transitions between exotic states of matter.
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2022-10-27
Seminar Report
iTHEMS Biology Seminar by Dr. Hiroyuki Ebata on October 27, 2022
On October 27th, Dr. Ebata talked about experiments and theoretical modeling of cell migration dynamics. In the introductory part, he explained the relation between fluctuations of the cell shape and migration dynamics, as well as the basics of durotaxis. After reviewing the experimental setups, he showed us the experimental results of cell migration dynamics on hydrogels with heterogeneous stiffness. He constructed models based on symmetry arguments and consistently explained the observed phenomena. We really enjoyed his clear talk with plenty of exciting movies on cell migration. Reported by Kyosuke Adachi
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2022-10-27
Press Release
Probing Quark Matter with Gravitational Waves - Reading Traces of Ultra-Dense Matter from Gravitational Waves after Neutron Star Mergers
An international research group including Yongjia Huang (Student Trainee, iTHEMS) and Shigehiro Nagataki (Deputy Program Director, iTHEMS) has performed numerical simulations based on general relativity for the merger of binary neutron stars and shown that the waveform of gravitational waves emitted after the merger provides detailed readings of the properties of ultra dense matter with a density of over 1 trillion kg per cm3. This research result is expected to contribute to the clarification of the internal structure of neutron stars and the properties of ultra-dense matter in gravitational wave astronomy. For details, please see the related link.
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2022-10-27
Paper of the WeekWeek 5, October 2022
Title: Bump of sound velocity in dense 2-color QCD Author: Etsuko Itou, Kei Iida arXiv: http://arxiv.org/abs/2210.14385v1 Title: High-energy properties of the graviton scattering in quadratic gravity Author: Yugo Abe, Takeo Inami, Keisuke Izumi arXiv: http://arxiv.org/abs/2210.13666v1 Title: Double and Quadruple Flat Bands tuned by Alternative magnetic Fluxes in Twisted Bilayer Graphene Author: Congcong Le, Qiang Zhang, Cui Fan, Xianxin Wu, Ching-Kai Chiu arXiv: http://arxiv.org/abs/2210.13976v1 Title: Slowly Decaying Ringdown of a Rapidly Spinning Black Hole: Probing the No-Hair Theorem by Small Mass-Ratio Mergers with LISA Author: Naritaka Oshita, Daichi Tsuna arXiv: http://arxiv.org/abs/2210.14049v1 Title: Neutron star mass formula with nuclear saturation parameters for asymmetric nuclear matter Author: Hajime Sotani, Shinsuke Ota arXiv: http://arxiv.org/abs/2210.11651v1
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2022-10-25
Hot Topic
The RIKEN-Berkeley Center was featured in RIKEN Overseas Office Newsletter
The RIKEN-Berkeley Center was featured in the Oct. 2022 issue of "News from RIKEN's Overseas Offices". The title of the article written by Adam Phillips in the RIKEN International Affairs Division is "What makes institutional international collaborations work?". Enjoy the article!
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2022-10-24
Seminar Report
iTHEMS Theoretical Physics Seminar by Prof. Elisa G.M. Ferreira on October 11, 2022
In her talk, Dr. Elisa Ferreira exploited some of the intriguing models of dark matter (DM), one of the biggest mysteries in cosmology. While there are many different models to explain the nature of this elusive component, she presented a class of dark matter models: ultra-light dark matter (ULDM) or ultra-light axions (ULA). She explained that one of the most interesting features of this class of DM models is that it might condense in the interior of the halos of galaxies forming a Bose-Einstein condensate or superfluid. This interesting quantum phenomena on macroscopic scales, and the wave nature of ULDM leads to different and interesting astrophysical consequences that can be probed on small scales. She first reviewed the fuzzy dark matter model, one of the most well studied ULA models, and then introduced the DM superfluid model. Upon condensation in the interior of galaxies, DM dynamics in this model can represent that of so-called modified Newtonian dynamics on galactic scales. Dr. Ferreira showed the theoretical description of this model and its interesting phenomenology, especially on small scales. Reported by Ryo Namba
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2022-10-24
Seminar Report
iTHEMS Seminar by Dr. Filippo Anzuini on September 27, 2022
The main focus of Dr. Filippo Anzuini's talk was on axions, which are pseudo-Goldstone bosons that provide a solution to the strong CP problem, and are prominent candidates for dark matter. In neutron stars, it has been shown recently that the potential of the QCD axion acquires finite density corrections that shift the axion field expectation value, which can be large compared to the vanishing expectation value in vacuum. Such a shift leaves an imprint on typical neutron star observables such as the redshifted thermal luminosity, which can be used to constrain the axion parameter space. In his talk, Dr. Anzuini discussed the coupling of axions with photons, which modifies Maxwell’s equations and alters the neutron star magnetic field. By performing state-of-the-art magneto-thermal simulations, he performed his calculations of the axion-induced perturbations to the neutron star’ magnetic field, and showed that they grow on relatively short time-scales. Intense electric currents then lead to enhanced ohmic dissipation, increasing the stars’ observable thermal luminosity. The activation of such mechanisms depends on the axion decay constant and the axion mass. His results indeed opened a new astrophysical avenue to constrain axions, extending significantly the parameter range that can be probed with direct axion searches. Reported by Ryo Namba
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2022-10-24
Seminar Report
iTHEMS Theoretical Physics Seminar by Dr. Yuko Urakawa on July 27, 2022
In her talk, Prof. Yuko Urakawa discussed the generalized deltaN formalism of cosmological perturbations, which dramatically facilitates a computation of the primordial density perturbation and the primordial gravitational waves. In particular, she addressed a violation of the cosmological principle, namely a violation of the global isotropy in the Universe. A major implication of her study is that measuring the PGWs provides a powerful tool to explore a violation of the global isotropy. Such effects can potentially be searchable by the future space-based CMB polarization mission LiteBIRD. Reported by Ryo Namba
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2022-10-21
Seminar Report
iTHEMS Biology Seminar by Mr. Keiichi Morita on October 20, 2022
I talked about my research progress about a mathematical model on how interspecific pollen transfer can affect coexistence and evolution of sex allocation. First, analytical results without evolution showed that interspecific pollen transfer had negative impacts on coexistence by preventing fertilization in the other species. Also, asymmetry of sex allocation between species promoted extinction of either species. Second, analytical results with evolution of sex allocation revealed that sex allocation always evolved into one regardless of strength of interspecific pollen transfer. Although my model is very tough to understand, thank you for your listening and giving me comments! Reported by Keiichi Morita
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2022-10-20
Paper of the WeekWeek 4, October 2022
Title: Competition between pairing and tripling in one-dimensional fermions with coexistent s- and p-wave interactions Author: Yixin Guo, Hiroyuki Tajima arXiv: http://arxiv.org/abs/2210.07042v1
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2022-10-14
Seminar Report
iTHEMS Biology Seminar by Dr. Lazaro-Guevara Jose Miguel on October 6, 2022
On October 6th, 2022, we had the pleasure to have José Miguel Lázaro-Guevara, a postdoctoral researcher at the University of British Columbia, in our Biology seminar. His talk was related to pharmacogenomics. The idea behind the field of pharmacogenomics is that the effectiveness of drugs in medical treatments is partially determined by the genetic variation of patients, but producing genome-wide data for one patient is costly and not affordable for many patients or insurance companies. For these cases, Lázaro-Guevara proposes using an extreme-low coverage genotyping, which consists on sequencing random sections of the genome of on a patient. By doing so, it is possible to later use a background reference (the genome of other genetically related people) to apply an imputation method to infer the parts of the genome that were not directly sequenced. By showing clinical cases on patients from a population from Utah, USA, the extreme-low coverage method seems to be a reliable and effective method to detect associations between genetic variation and the effectiveness of drug treatment. Reported by José Said Gutiérrez-Ortega
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2022-10-13
Seminar ReportiTHEMS Math Seminar by Mr. Hayato Imori on July 25, 2022
On July 25, there was a math seminar by Dr. Hayato Imori. He gave a talk entitled Introduction to instanton knot homology. In the first part of his talk, the speaker explained the fundamental construction of Morse homology for finite dimensional manifolds by giving concrete examples of Morse functions. He then explained how the discussion extends to the case of infinite dimensional manifolds obtained by singular connections. Reported by Masaki Taniguchi
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2022-10-13
Paper of the WeekWeek 3, October 2022
Title: Exotic codimension-1 submanifolds in 4-manifolds and stabilizations Author: Hokuto Konno, Anubhav Mukherjee, Masaki Taniguchi arXiv: http://arxiv.org/abs/2210.05029v1 Title: Lattice QCD studies on decuplet baryons as meson-baryon bound states in the HAL QCD method Author: Kotaro Murakami, Yutaro Akahoshi, Sinya Aoki, Takumi Doi, Kenji Sasaki arXiv: http://arxiv.org/abs/2210.05395v1 Title: Effects of nuclear matter and composition in core-collapse supernovae and long-term proto-neutron star cooling Author: Kohsuke Sumiyoshi, Shun Furusawa, Hiroki Nagakura, Akira Harada, Hajime Togashi, Ken'ichiro Nakazato, Hideyuki Suzuki arXiv: http://arxiv.org/abs/2209.02474v1 Title: DMRG study of the higher-charge Schwinger model and its 't Hooft anomaly Author: Masazumi Honda, Etsuko Itou, Yuya Tanizaki arXiv: http://arxiv.org/abs/2210.04237v1 Title: AdS/BCFT from Conformal Bootstrap: Construction of Gravity with Branes and Particles Author: Yuya Kusuki, Zixia Wei arXiv: http://arxiv.org/abs/2210.03107v1
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2022-10-11
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Ryo Namba on October 7, 2022
Blazar observations have provided tantalizing evidence for the presence of magnetic fields in the extragalactic regions, where astrophysical processes may not be an efficient source for their generation. While a natural speculation is to associate the production of such large-scale magnetic fields to inflationary physics, it has been known that magnetogenesis solely from inflation is quite challenging. In this talk Dr. Ryo Namba discussed some mechanisms, successful/unsuccessful, for production of magnetic fields in the primordial universe, as well as the constraints from theoretical consistencies and observational data. Reported by Shigehiro Nagataki
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2022-10-06
Hot Topic
MACS-iTHEMS Study Group Members visited Wako on September 20-21, 2022
MACS Program in the Faculty of Science, Kyoto Univ. has several Study Groups (SG) and one of them is the MACS-iTHEMS SG. In 2022, Ryosuke Iritani and Jeffery Fawcett from iTHEMS are actively participating in this MACS-iTHEMS SG and interacting with the students in Kyoto Univ. On Sep.20 and 21, nine students (including undergraduate and graduate students in various fields at Kyoto Univ.) together with three faculty members (Kobayashi san, Tomida san and Itami san) from MACS Program visited RIKEN Wako Campus. On the afternoon of Sep.20, they visited Enoto lab. to learn Enoto san's thundercloud project and NinjaSat project. Then they moved to CBS to see Brain Box exhibition. After that, they had a scientific session to explain their own research to each other at the iTHEMS common room. On the morning of Sep.21, after a brief introduction to the iTHEMS activities and facilities, they had a tour of the gigantic accelerator complex (RIBF) in Nishina Center. On the afternoon of the same day, they visited the Chemical Biology Lab. in CSRS, followed by a visit to Toyoizumi Lab. in CBS to attend Toyoizumi san's lecture on neural learning theory. It was a very stimulating and intensive program for the students. In particular, the Scientific Session on the afternoon of September 20, from 5:00 to 8:30 p.m., featured lively questions and discussions between RIKEN researchers and students. We will continue this program and visit in the coming years.
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2022-09-29
Paper of the WeekWeek 5, September 2022
Title: Dirac Fermion kinetics in three-dimensionally curved graphene Author: Yoichi Tanabe, Yoshikazu Ito, Katsuaki Sugawara, Mikito Koshino, Shojiro Kimura, Tomoya Naito, Isaac Johnson, Takashi Takahashi, Mingwei Chen doi: https://doi.org/10.1002/adma.202005838 arXiv: http://arxiv.org/abs/2010.03601v2
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2022-09-27
Award
Dr. Naritaka Oshita received the "17th Seitaro Nakamura Prize"
Our colleague Dr. Naritaka Oshita (Special Postdoctoral Researcher, iTHEMS) has received the "17th Seitaro Nakamura Prize." This prize recognizes the achievements of young researchers in the field of particle physics in a broad sense. The winning paper is entitled "Ease of excitation of black hole ringing: Quantifying the importance of overtones by the excitation factors." The award ceremony will be held in March 2023 at the Spring Meeting of the Japanese Physical Society. Congratulations, Naritaka!
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2022-09-27
Hot Topic
Farewell message from Dr. Michiya Mori
Our colleague Michiya Mori moves on to a new carrier at Graduate School of Mathematical Sciences, The University of Tokyo as of October 1st. We all will miss him and wish him the best of luck in his latest endeavor. Here is a message from Michiya Mori: I spent 1.5 years at iTHEMS as a special postdoctoral researcher. It was a very great experience for me (as a mathematician) to have an opportunity to communicate with scientistists from various backgrounds (not only mathematics). I am grateful to everyone. I can fortunately continue to be a member of iTHEMS as a visiting scientist. I hope to get closer to more iTHEMS members in the future. From October, I become a project assistant professor of The University of Tokyo at Komaba Campus. Luckily iTHEMS has a satellite office in Komaba (SUURI-COOL Komaba). Probably I will sometimes be there, and I hope to see you again there soon!
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2022-09-26
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Filippo Anzuini on September 26, 2022
Neutron stars challenge current models of highly dense matter. Despite being the targets of numerous observational campaigns (e.g. gravitational-wave searches and X-ray observations), their equation of state is still unknown. One of the most exciting possibilities is that “unconventional” particles such as hyperons may appear in neutron star cores. Hyperons have a major impact on the observed thermal luminosity, because they accelerate the cooling rate via direct Urca processes, which copiously increase the neutrino emission from the core. Such mechanism is often considered to be a key signature of hyperon concentrations at high densities. Hyperon superfluidity plays a major role as well, because it can suppress the neutrino emissivity exponentially. The hope is that a comparison of the theoretical cooling curves against the available data of thermally-emitting neutron star can hint towards the existence of hyperons and their superfluidity. There is one ingredient, however, that is often neglected in neutron star cooling models: internal heating. The magnetic field of neutron stars decays due to the dissipation of the electric currents circulating in the crust, generating substantial Joule heating in the shallower layers. The thermal power generated by this process can counterbalance hyperon fast cooling, making it difficult to infer the presence of hyperons from the available thermal luminosity data, and complicating the link between measured thermal emission and internal composition. The speaker showed that this is the case for magnetars, because their crustal temperature is almost independent of hyperon direct Urca cooling in the core, regardless of whether hyperons are superfluid or not. Likewise, thermal luminosity data of moderately magnetized neutron stars are not suitable to extract information about the internal composition, as long as hyperons are superfluid. During/after the talks, there were some interesting questions and discussions. The seminar was done in a hybrid style. Reported by Shigehiro Nagataki
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2022-09-22
Paper of the WeekWeek 4, September 2022
Title: Vertex operator algebra and colored parenthesized braid operad Author: Yuto Moriwaki arXiv: http://arxiv.org/abs/2209.10443v1 Title: Berry's phase and chiral anomalies Author: Kazuo Fujikawa, Koichiro Umetsu arXiv: http://arxiv.org/abs/2209.08334v1 Title: Squeezing stationary distributions of stochastic chemical reaction systems Author: Yuji Hirono, Ryo Hanai arXiv: http://arxiv.org/abs/2209.08787v1
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2022-09-21
Seminar Report
Report of DM3 Workshop on September 15-17, 2022
Please enter the seminar report here!The study of dark matter (DM) has a long history. It starts in the 1930s from the article that Zwicky pointed out the existence of a huge invisible mass in galaxy clusters. We now know that about a quarter of the total energy density of the Universe is occupied by DM. But we still do not understand its nature, even we do not know whether or not it is a particle. We have three kinds of strategies to probe DM so-called collider, direct detection, and indirect detection experiments. By establishing a smooth connection between each other with theoretical support, we should approach a better understanding of DM. With this rationale, the iTHEMS DM working group held an international workshop "DM3- Deep insights and Multiple strategies for Deciphering the Mystery of Dark Matter" during Sep.15-17. The theme of the workshop can be summarized as just a simple question, "what is DM for you?" The workshop was composed of 18 invited talks for reviews of various DM studies and a poster session for individual presentations. The 1st day has been devoted to the discussion about DM search with astrophysical objects. On the 2nd day, we paid much attention to the particle nature of DM. Novel ideas for candidates and techniques to probe a huge parameter space of DM are exhibited. We went through the intersection between cosmic-ray study and DM search on the final day of the workshop. The latest status of the DM study was presented in posters. Throughout the workshop, attendees discussed the nature and probe for DM regarding multiple aspects. According to the follow-up questionnaire, they said that "there are differences between the view before and after the workshop" and "would like to continue studying DM". After the workshop, we reconsider the question again: "what is DM for you?" There have been so many answers to the question till now. Continuing the study of DM, we believe that we see a consensus someday. Reported by Nagisa Hiroshima
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2022-09-20
Announcement
Dr. Yuki Yokokura and Dr. Enrico Rinaldi will appear in the NHK TV program Cosmic Front
Our iTHEMS colleague, Dr. Yuki Yokokura and Dr. Enrico Rinaldi, will appear in the NHK TV program Cosmic Front "Relativity vs. quantum theory: the event horizon and the dance of different dimensions" Do not miss it ! First broadcast date: September 22, 2022 at 10:00 p.m.
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2022-09-16
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Naomi Tsuji on September 16, 2022
The MeV gamma-ray domain is the only unexplored window among recent multiwavelength observations in astrophysics, often referred to as the "MeV gap". To fulfill this gap, there are several ongoing and planned projects of MeV gamma-ray telescopes. The measurement of MeV gamma rays (both continuum and line emission) would give us new insight into many topics in astrophysics, such as relativistic jets, particle acceleration, and origin of matter. In advance of the future MeV gamma-ray missions, we have been working on prediction of the MeV gamma-ray sky, which is helpful to determine what kinds of sources can be detectable with the future telescopes. In order to explore the MeV gamma-ray sources, Tsuji-san and her collaborators performed a catalog cross-matching between the hard X-ray (Swift/BAT) and GeV gamma-ray (Fermi/LAT) catalogs, resulting in 145 firmly cross-matched sources. Combined with the Galactic diffuse emission, which is calculated by GALPROP to reconcile the cosmic-ray and gamma-ray spectra with observations by AMS-02, Voyager, and Fermi-LAT, the all-sky maps in the MeV gamma-ray band can be produced. This is also used to investigate a long-standing problem in the MeV gamma-ray astrophysics: the origin of the diffuse emission from the inner Galaxy, measured by COMPTEL. Tsuji-san reported the analysis and results in detail, and introduce future missions of the MeV gamma-ray detectors. There were useful discussions among the speaker and audience during/after the talk. Reported by Shigehiro Nagataki
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