セミナーレポート
356 ニュース

20240226
セミナーレポートMathPhys Seminar by Christy Koji Kelly on February 26, 2024
Christy gave an introductory talk on distribution and AQFT. Reported by Yuto Moriwaki

20240219
セミナーレポートABBLiTHEMS Joint Astro Seminar by Yosuke Mizuno on February 8, 2024
On February 8th, Prof. Yosuke Mizuno (Shanghai Jiao Tong University) gave a talk about the numerical simulations of the jet launching process at the vicinity of black holes. Supermassive black holes hosted in active galaxies are known to launch relativistic jets and emit electromagnetic signals across a wide range of energy bands. A notable example is the nearby supermassive black hole hosted in the M87 galaxy. Recent results from the Event Horizon Telescope, which has provided a radio image of the vicinity of the black hole, have revealed a signature of curved spacetime. In the talk, after giving a broad overview of this topic, he described the current understanding of the physics at the horizon scale of black holes based on his numerical simulations. He carried out 3D general relativistic magnetohydrodynamical simulations and general relativistic radiative transfer calculations to investigate the jet launching process and the radiative signature at the horizon scale. He has shown that his calculations can successfully reproduce the results of the Event Horizon Telescope. At the same time, while it is robust that the curved spacetime signature is present in the observation, uncertainty remains in the physical properties such as the spin of black hole and the degree of magnetization of the accretion flow. To further pin down these properties, higher quality observational data are required. Reported by Hirotaka Ito

20240130
セミナーレポートQuantum Computation SG Seminar by Emanuele Mendicelli on December 18, 2023
Dr. Emanuele Mendicelli presented his work on the study a SU(2) pure gauge lattice theory on a quantum annealer by DWave. Reported by Enrico Rinaldi

20240104
セミナーレポートiTHEMS Math Seminar by Yuto Yamamoto on December 13, 2023
There was a math seminar by Yuto Yamamoto. He explained what is a tropical geometry first. He then explained the periodic integral and his recent results. Reported by Keita Mikami

20231228
セミナーレポートQuantum Matter Seminar by Yuji Hirono on December 22, 2023
On December 22nd, Professor Yuji Hirono from Kyoto University gave an online seminar talk in Quantum Matter Study Group, exploring the intricate world of fractonic phases. His talk, titled "A symmetry principle for gauge theories with fractons," ran from 5pm to 6:15pm JST. Taking center stage were fractons, unusual quasiparticles with a surprising quirk – they are practically immobile when alone. A key feature of the fractons, making them distinct from typical topological objects, is that their stability is not protected by an energy gap. Instead, it is the underlying symmetries that guarantee their properties. Professor Hirono used simple examples, like the conservation laws of dipoles and the connection to the immobility, to illuminate this unique property. This immobility sets fractons apart from the more conventional particles that we are familiar with, sparking fascination and curiosity about their underlying mechanisms. Central to his discussion was the formulation of effective theories based on the spontaneous breaking of these nonuniform symmetries. At low energies, these theories simplify into known higherrank gauge theories, such as scalar/vector charge gauge theories. The gapless excitations in these theories are interpreted as Nambu–Goldstone modes for higherform symmetries. A novel aspect highlighted was the acquisition of a gap by some modes due to the nonuniformity of the symmetry, analogous to the inverse Higgs mechanism in spacetime symmetries. This framework elucidates the mobility restrictions of fractons as determined by the commutation relations of charges with translations. This illuminating seminar offered a glimpse into the remarkable world of fractonic phases and the power of novel symmetry principles. Reported by ChingKai Chiu

20231225
セミナーレポートiTHEMS Biology Seminar by Takara Nishiyama on December 19, 2023
In this seminar, Mr. Nishiyama delivered a lecture primarily on a cohort study of COVID19, focusing on the application and interpretation of mathematical models. The content of this lecture provided us, the audience, with extremely valuable insights in the context of how to give back to society through mathematical modeling. In particular, he demonstrated how things that are not apparent in normal statistical analysis can be quantitatively compared and interpreted through mathematical models and parameter estimation. He also proposed a simple model for parameter estimation, which is feasible even with few data points and highly heterogeneous data, and applied this model. Therefore, we were able to see the essence of datadriven mathematical research. This lecture was a very meaningful event from both the perspectives of research content and research approach. Reported by Daiki Kumakura

20231218
セミナーレポートiTHEMS Theoretical Physics Seminar by Ryotaro Sano on December 4, 2023
In this seminar, Mr. Sano presented their study on magnon hydrodynamics for ultraclean ferromagnets. A set of coupled hydrodynamic equations for a magnon fluid are derived and the spin and thermal conductivities are studied by focusing on the most dominant time scales. As a hallmark of the hydrodynamic regime, the speaker and his colleagues reveal that the ratio between the two conductivities shows a large deviation from the socalled magnonic WF law. The drastic breakdown of the magnonic WF law results from the difference in relaxation processes between spin and heat currents, which is unique to the hydrodynamic regime. Therefore, the presented results will become key evidence for an emergent hydrodynamic magnon behavior and lead to the direct observation of magnon fluids. In the seminar, researchers with different backgrounds (ranging from condensed matter physics to nuclear physics and cosmology) asked a lot of questions, and a lively discussion ensued. Reported by Yuta Sekino

20231205
セミナーレポートJoint 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

20231126
セミナーレポートABBLiTHEMS 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

20231113
セミナーレポートiTHEMS 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
セミナーレポートiTHEMS 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

20231031
セミナーレポートDMWG 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
セミナーレポートDMWG 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

20231013
セミナーレポートiTHEMS 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
セミナーレポートABBLiTHEMS 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
セミナーレポートABBLiTHEMS 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

20231004
セミナーレポートiTHEMS 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

20230927
セミナーレポートABBLiTHEMS 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
セミナーレポートiTHEMS 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

20230918
セミナーレポートQuantum 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)

20230905
セミナーレポートLabTheory 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

20230825
セミナーレポートExploring 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

20230816
セミナーレポート3rd 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
セミナーレポートHigher 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

20230726
セミナーレポートQuantum Matter Seminar by Xinloong Han on July 24, 2023
On July 24th, 2023, quantum matter SG hosted a seminar entitled "Electronic instabilities emerging from higherorder van Hove singularities", and the guest speaker was Xinloong Han, a Postdoctoral Fellow at the Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, China. Xinloong Han started by introducing van Hove singularity (VHS). Building on the conventional understanding of VHS points, Han introduced the concept of higherorder VHSs, which have recently been explored in ABCstacked trilayer graphene and twisted bilayer graphene. He elucidated the differences between conventional VHSs and higherorder VHSs, paving the way for a discussion on the enhanced nematicity driven by large flavor number with higherorder VHSs on the square and Kagome lattices. Towards the conclusion of his talk, Han shed light on the possibility of robust topological superconductivity emerging on the square lattice due to the interplay of spinorbital coupling and higherorder VHSs. This revelation presented a captivating insight into the advancements in the study of topological superconductors. Reported by ChingKai Chiu

20230720
セミナーレポートDMWG Seminar by Slivia Manconi on July 10, 2023
As a nature of dark matter that feels gravity, dark matter in our Universe forms halos, which are gravitationallybounded macroscopic structures. The halo structure is highly hierarchical and the halo of our Milky Way, for example, hosts many subhalos inside. However, smaller halos below a certain scale could not be visible because they cannot host galaxies. If we look at the sky in gammaray wavelength, there are lots numbers of bright sources. Most of them are socalled active galactic nuclei (AGN), which are related to the powerful jet activities of black holes. A certain portion of point sources are not categorized yet. They could be AGNs, while it is also possible that they are bright due to DM annihilation occurring in compact and small subhalos in our Galaxy. Neural networks, which are tools we have obtained in this era, powerfully help us to obtain insights into the properties of unknown gammaray sources. Properties of known sources such as spectrum and population serve as data for the supervision of the neural network. The trained network is used to look for outliers in the gammaray unknown sources which can be candidates for subhalos emitting gammarays by DM annihilations. In this way, a conservative upper limit on the annihilation crosssection of DM is derived. The scheme is highly flexible and has many possibilities for extensions. In the near future, a huge amount of data, which is far beyond human ability to analyze all, from experiments in multiple wavelengths and probes should appear. The future of DM study assisted with machine learning should be bright. Reported by Nagisa Hiroshima

20230707
セミナーレポートABBLiTHEMS Joint Astro Seminar by Takatoshi Ko on July 7, 2023
Iras 00500+6713 is a bright nebula in the infrared, and Xray observations show it consists of diffuse region and strong illuminated central region. In addition, optical spectral observations have recently revealed that fast wind with about 15,000 km/s is blowing from the massive white dwarf at the center. The properties of this nebula and white dwarf are very similar to those theoretically predicted by the binary white dwarf merger. In addition, its position on the celestial sphere and the extent make it a prime candidate for the remnant of SN 1181, a historical supernova. In this seminar, Mr. Takatoshi Ko proposed that such a multilayered structure is formed by the collision between the remnant of SN 1181 and the stellar wind blowing from the central white dwarf, and succeeded in constructing a model that is consistent with the multiwavelength observations. The results show that the progenitor of SN 1181 is a binary white dwarf with 1.31.9 solar mass and that their merger triggered an explosion that ejected mass with 0.20.6 solar mass to form the present object. The extent of the Xray source concentrated in the center reveals that these winds began blowing within the last 30 years, and Mr. Takatoshi Ko discussed this property as well. Reported by Shigehiro Nagataki

20230619
セミナーレポートiTHEMS Biology Seminar by Dr. Yu Okamura on May 25, 2023
We had the pleasure to have Dr. Yu Okamura (The University of Tokyo) as an invited speaker of our Biology seminar of May 25th, 2023. Dr. Okamura introduced us to the mechanism that allow herbivory of Pieris butterflies on Brassicaceae plants (plants of the group of the mustard). Brassicaceae, as well as most plants, will defend from herbivores by producing chemical compounds that can be lethal, but at the same time, insects will need to evolve strategies to elude the chemical defenses of the plants. This relationship leads to an interesting coevolutionary pathway that has not been widely explored from the genomic perspective. In his study system, Dr. Okamura has performed experiments to research how the toxic chemical compounds derived from glucosinolates of plants are eluted by their butterfly herbivores thanks to the expression of two specific genes that produce proteins that decompose the glocusinolates into nonlethal metabolites. One of the two genes (NSP gene) is known to be expressed in most Pieris butterflies that feed on Brassicaceae plants, but in his research, Dr. Okamura found that another gene (MA gene) is complementary of the effect of the NSP gene. Using genome editing techniques (CRISPR/Cas9), Dr. Okamura showed that the absence of NSP or MA genes can be lethal for herbivores. It is concluded that, in combination, NSP and MA genes are necessary for Pieris butterflies to maintain herbivory on a wide variety of plants in the Brassicacae family. Reported by José Said GutiérrezOrtega

20230613
セミナーレポートiTHEMS Math Seminar by Mr. Kan Kitamura on June 7, 2023
In iTHEMS Math Seminar on June 7, 2023, Kan Kitamura gave us a talk on his recent research on quantum groups. In the first half of the talk, he introduced the definition of C*algebras and compact quantum groups. In the latter half of the talk, he explained his theorem on the classification of the discrete quantum subgroups of the quantum double of qdeformed simple Lie groups. The talk was highly clear and stimulating. Reported by Mizuki Oikawa

20230601
セミナーレポートQuantum uncertainty of fields and its effect on entanglement generation in quantum particles by Mr. Yuki Sugiyama on May 31, 2023
The unification of gravity and quantum mechanics is one of the important problems. To elucidate the theory of quantum gravity, it is becoming more and more important to get any hint of the quantum nature of gravity. In particular, the quantumgravityinducedentanglement of masses (QGEM) scenario, which is expected to observe the quantum nature of nonrelativistic gravity, has recently attracted great attention. In this talk, Sugiyamasan showed the effect of relativistic fields on entanglement generation based on quantum field theory. We also discussed the relationship between the entanglement generation and quantum uncertainty of the fields. Reported by Shigehiro Nagataki

20230531
セミナーレポートiTHEMS Theoretical Physics Seminar by Dr. Masaki Tezuka on May 30, 2023
On May 30, Dr. Masaki Tezuka gave a talk on Spectral correlations and scrambling dynamics in SachdevYeKitaev(SYK) type models. He explained his recent studies on quantum chaotic features, quantum scrambling, and connections to holography and quantum error corrections in the SYKtype models. Reported by Yuta Sekino

20230528
セミナーレポートExploring GPT’s Influence on Natural Science and Mathematics on May 17, 2023
The emergence of ChatGPT has shocked the world. Its influence on our society is inestimable, both for its possibility and its potential risk. Together with MLPhys (Foundation of “Machine Learning Physics”), we held a workshop “Exploring GPT’s Influence on Natural Science and Mathematics” on 17th May, to discuss the influence of GPT particularly on natural science and mathematics. An introductory lecture on GPT (generative pretrained transformer) and LLM (large language model) was given by Mr. Shota Imai (The University of Tokyo), and an introductory lecture on proof assistant system (automated theorem proving) was given by Dr. Yoshihiro Mizoguchi (Kyushu University). Around 30 people attended in place, and over 400 people attended the workshop online. Lively discussion took place among specialists of Mathematics, Physics and Computer science. Reported by Taketo Sano (iTHEMS, RIKEN)

20230526
セミナーレポートMathPhys Seminar by Dr. Masazumi Honda on February 16, 2023
On Febururary 16, Masazumi Honda gave a talk. He explained his recent results on the relationship between Riemann hypothesis and fourdimensional N=4 supersymmetric YangMills theory. Reported by Keita Mikami

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セミナーレポートiTHEMS Math Seminar by Dr. Kohei Hayashi on May 24, 2023
On May 24, there was a math seminar by Kohei Hayashi. In the first part of his talk, he start by explaining the idea of the hydrodynamic limit and the fluctuating hydro dynamic limit. He then explained Markov chain and how to obtain the diffusion equation. In the second part, he explained KPZ equation and its universality. Reported by Keita Mikami

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セミナーレポートABBLiTHEMS Joint Astro Seminar by Mr. Vincenzo Sapienza on May 19, 2023
Synchrotron Xray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high energy electrons accelerated at the shock front. Mr. Sapienza and his collaborators performed a spatially resolved spectral analysis of the young Kepler's SNR, where they identify two different regimes of particle acceleration. In the north, where the shock interacts with a dense circumstellar medium (CSM), they found a more efficient acceleration than in the south, where the shock velocity is higher and there are no signs of shock interaction with dense CSM. They also studied the temporal evolution of the synchrotron flux, from 2006 to 2014. A number of regions show a steady synchrotron flux and equal cooling and acceleration times. However, they found some regions where they measured a significant decrease in flux from 2006 to 2014. Our results display a coherent picture of the different regimes of electron acceleration observed in Kepler's SNR. Also Mr. Sapienza presented some preliminary results on the SN 1987A project. Reported by Shigehiro Nagataki

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セミナーレポートSpring Workshop on Quantum Gravity on April 26, 2023
Spring Workshop on Quantum Gravity, the first one in the lecture series Quantum Gravity Gatherings and cosponsored by NCTS, was a great success with about 50 participants, including some from Taiwan. First, Prof. Kawai's intensive lecture on quantum gravity was wonderful. In the basic part of the first half, he explained the physical aspects of the ordinary formulas found in textbooks on general relativity, from a quantum theoretical standpoint, and transformed the equations consistently, to arrive at physically clear results about quantum gravitational fields. In the latter part, he described the features of fieldtheoretic quantum gravity and its limitations. Through these, he showed us the importance of researching quantum gravity step by step from a fundamental point of view. All participants were interested in quantum gravity, and there was an atmosphere of togetherness in the room. During the lecture, a variety of questions, from the simple to the fundamental, were raised. During breaks, small discussions spontaneously occurred here and there in the common space. And in the short talk sessions, we were able to share each other's research and interests. The banquet on the first day of the event was a great opportunity to deepen friendship. Thus, this event provided many opportunities for learning, research, and exchange for the younger generation. Reported by Yuki Yokokura

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セミナーレポートDMWG Seminar: DMline search in the Galactic Center with MAGIC telescope
Among kinds of dark matter (DM) candidates, weakly interacting massive particles (WIMPs) are the most intensively studied ones along their theoretical background and expectations for the signals in onEarth experiments. However, up to now, our understanding of the regime of m>O(1) TeV is still limited since we cannot produce them at colliders and cannot expect a sufficient interaction rate at underground recoil detectors. Highenergy astrophysical observations are powerful in probing that regime and projects all over the world are now searching for corresponding signals. When we look for signatures of DM from astrophysical data, it is necessary to consider contributions from astrophysics very carefully. The key signatures could be the morphology of the emission, the spectrum, and correlating signals in other kinds of observations, variabilities, and so on. If DM particles annihilate to produce photon pairs, the spectrum should show a monochromatic peak corresponding to the mass of DM, hence it is distinctive against the astrophysical emissions. MAGIC telescope, which locates in the Northern Hemisphere, only considers target objects in the northern sky previously. However, it actually can see the Galactic Center in a large inclination. For this case, the threshold of the analysis is worsened but the effective area is improved, then it can achieve a good sensitivity to highenergy emissions. Using 223h of observation at the Galactic Center with MAGIC, the line emission search is carefully performed. The determination of the "off" takes an important role in not overestimating the sensitivity and the sliding window technique is adopted regarding this point. The uncertainty of the DM density of the region of interest is also carefully discussed by performing the analysis applying both the cuspy and cored profiles. No signatures of the monochromatic gammaray from DM annihilation are found in this analysis hence we obtain upper limits of the annihilation crosssection. The sensitivity is comparable to the flux level of a wellmotivated Wino DM model which should exhibit annihilation lines around E~3TeV. This means that we are now approaching the era that to probe detailed particle models of DM with astrophysical observations. In the near future, observations with the Cherenkov Telescope Array will start operations and we can look into the detail of the models in combination with particle physics communities! Reported by Nagisa Hiroshima

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セミナーレポートiTHEMS Biology Seminar by Mr. Naoki Konno on April 20, 2023
In April 20, Mr Naoki Konno (University of Tokyo) gave a fantastic talk about the machine leaning method for the prediction of evolution. The talk was entitled, “Machine learning predicts biological system evolution by gene gains and losses”. To my knowledge, this study using genome data of ~3000 species is one of few seminal attempts to theoretically predict longterm and systemlevel evolution. The seminar by Konno san was very clear and we understood the predictability of the proposed framework, called “Evodictor”. In the beginning of the talk, he kindly explained the theoretical basis about phylogenetic tree estimation and machine learning for nonspecialists for which we could enjoy and learn from his seminar a lot. Thank you, Konnosan for the great talk!! Reported by Gen Kurosawa

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セミナーレポートABBLiTHEMS Joint Astro Seminar by Dr. Kumiko Kotera on April 18, 2023
We are living exciting times: we are now able to probe the most violent events of the Universe with diverse messengers (cosmic rays, neutrinos, photons and gravitational waves). One challenge to complete the multimessenger picture resides in the highest energies, as no ultrahigh energy neutrinos have been observed yet. This challenge could be undertaken by the GRAND (Giant Radio Array for Neutrino Detection) project, which aims at detecting ultrahigh energy particles, with a colossal array of 200'000 antennas over 200'000 km2, split into ~20 subarrays of ~10'000 km2 deployed worldwide. In this talk, Kumiko Kotera presented preliminary designs and simulation results, plans for the ongoing, staged approach to construction, and the rich research program made possible by the proposed sensitivity and angular resolution. Reported by Shigehiro Nagataki

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セミナーレポートSeminar, "Introduction to the Renormalization group method as a powerful reduction method of dynamics" by Dr. Teiji Kunihiro on April 10, 2023
In April 10, Dr Teiji Kunihiro (Prof Emeritus, Kyoto Univ) gave an introductory talk about the renormalization group method, entitled “Introduction to the Renormalization group method as a powerful reduction method of dynamics.” In fact, this talk was the first seminar at our new seminar room #359 with the splendid blackboard in RIKEN Wako Campus. The talk by Kunihirosan using the blackboard was very very clear, and we can understand the power of the Renormalization group method and its applicability [1]. The talk was also delivered via Zoom (i.e. ~35 participants in total), and there were lively discussions between the lecturer and the audience. After the talk, he kindly shared his lecture note with us so that we can take advantage of it. Thank you, Kunihirosan for the wonderful talk!! Reported by Gen Kurosawa

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セミナーレポートLabTheory Standing Talks #1 by Dr. Hideshi Ooka on March 16, 2023
The first LabTheory standing talk took place on March 16th, 2023, inviting Hideshi Ooka from CSRS (Riken Center for Sustainable Resource Science). He picked up the chemical process of making hydrogen from water as the subject. By design, the event is organized in a very informal setting."I was glad that the speaker prepared very few slides and all the slides were simple because it gave the audience an opportunity to ask many random questions in all sorts of direction," one of the participants, Catherine Beauchemin says. As she says, "in this light and flexible format, it is the audience that can decide what aspects are more interesting for them and ask more questions about it," there have been many questions asked and discussions followed. The event appears to be fruitful for the speaker too; "I will share the comment with my colleagues, as I believe it is a chance to advance the level of chemistry in our lab, " Hideshi Ooka concludes. Reported by Tsukasa Tada

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セミナーレポートiTHEMS Biology Seminar by Dr. Yohei Nakayama on March 30, 2023
On March 30th, Dr. Nakayama talked about F1ATPase from both experimental and theoretical aspects. In the introduction, he reviewed biological molecular motors and experimental facts. Then he introduced a Langevin model for the kinetics of F1 and explained how a specific case of the model fits the previous experiments. In the main part, he told us about new experimental results, relation to the theoretical model, and theoretical prediction based on the model. We thank Dr. Nakayama for giving us an exciting presentation. Reported by Kyosuke Adachi

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セミナーレポートiTHEMS Biology Seminar by Dr. Midori Tuda on March 23, 2023
Dr. Tuda gave us a very wellprepared, clear and interesting presentation about her group's current research. Her work is primarily experimental, while iTHEMS Biology members' work is primarily theoretical, which could create interesting opportunities. We found many common interest between her research and that of iTHEMS Biology members, such as niche divergence under a changing climate (GutiérrezOrtega), sex ratio of offsprings (Hitchcock), and species coexistence/competition (Iritani). This gave rise to many interesting questions, comments and exchanges. We hope to continue conversation. Reported by Catherine Beauchemin

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セミナーレポートABBLiTHEMS Joint Astro Seminar by Dr. Ellis Owen on March 10, 2023
Ultra highenergy (UHE) cosmic rays (CRs) from distant sources interact with intergalactic radiation fields, leading to their spallation and attenuation through photohadronic processes. Their deflection and diffusion in large scale intergalactic magnetic fields (IGMFs), in particular those associated with Mpcscale structures, alter the cumulative cooling and interactions of a CR ensemble to modify their spectral shape and composition observed on Earth. In this talk, Ellis Owen demonstrated the extent to which IGMFs can affect observed UHE CRs, and showed that source population models are degenerate with IGMF properties. Interpretation of observations, including the endorsement or rejection of any particular UHE CR source classes, needs careful consideration of the structural properties and evolution of IGMFs. Future observations providing tighter constraints on IGMF properties will significantly improve confidence in assessing UHE CR sources and their intrinsic CR production properties. Reported by Shigehiro Nagataki

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セミナーレポートiTHEMS Biology Seminar by Dr. Adrian GonzalezCasanova on January 19, 2023
We had the pleasure to have Dr. Adrián GonzálezCasanova (Neyman Visiting Assistant Professor, The University of California, Berkeley, USA / Associate Professor, National Autonomous University of Mexico, Mexico) in our Biology seminar of January 19th, 2023. He presented us a talk consisting of two sections. First, he explained to us the basis of the coalescent theory: a model that depicts how alleles within a population relate each other until reaching a common ancestor. Second, he presented us how the coalescent theory can be used to explain and predict the behavior of one of the most intriguing experiments in evolutionary biology: the Lenski experiment. The Lenski experiment consists of a daily cultivation of E. coli; each day's culture is grown from a population cultivated the previous day. This, way, after thousand generations, the experiment has shown that the fitness increase of individuals is decelerating, but it doesn't decrease or even reach a plateau. Dr. GonzálezCasanova presented us some ideas of how we can model the underlying biological processes behind the experiment while considering other noisy processes such as epistasis or clonal interference, and thus better understand how evolution occurs. Reported by José Said GutiérrezOrtega

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セミナーレポートQuantum Matter Seminar by Dr. YungYeh Chang on March 2, 2023
On March 2nd, 2023, the iTHEMS Quantum Matter Seminar was held online, featuring a talk on "Topological Kondo Superconductors" by YungYeh Chang, a postdoctoral researcher at the National Center for Theoretical Sciences and National Yang Ming Chiao Tung University in Taiwan. YungYeh Chang began by introducing Kondo lattice and heavy fermion compound. Interestingly, superconductivity can emerge in this compound. Then, including topology, he proposed a realization of a 2D timereversal symmetric superconductor in a class of Kondo lattice materials. The proposed system involves the oddparity Kondo hybridization, which mediates ferromagnetic spinspin coupling and leads to spintriplet resonantvalencebond (tRVB) pairing between local moments. The speaker explained that spintriplet p±p' wave topological superconductivity is reached when the Kondo effect coexists with tRVB. By using the mean field theory to generate an effective free fermion (BdG) Hamiltonian, the topological nature was identified by the nontrivial topological invariant and the chiral Majorana modes at edges. The results on the superconducting transition temperature, Kondo coherent scale, and onset temperature of Kondo hybridization were discussed, which not only qualitatively but also quantitatively agree with the observations for UTe2. In summary, the iTHEMS Quantum Matter Seminar on "Topological Kondo Superconductors," presented by YungYeh Chang, provided an insightful discussion on the study of topological superconductors in Kondo lattice materials. The attendees had the opportunity to ask questions and engage in discussions with the speaker, making it an interactive and informative seminar. Reported by ChenHsuan Hsu (Academia Sinica, Taiwan) and ChingKai Chiu

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セミナーレポートDMWG Seminar by Dr. Jowett Chan on February 9, 2023
Dark matter (DM) of our Universe could be categorized into three types: cold DM (CDM), warm DM (WDM), or fuzzy DM (FDM) depending on its mass. CDM is the most wellstudied one with its success in largescale structure formations. However, as studies proceed, some problems arise in such models: observations of smallstructure would not match the predictions of CDM structures in simulations. For example, observations of Milky Way satellites indicate the existence of the central core while simulations predict cuspy structures at the center. The feature could be welldescribed by considering FDM of m~O(1e20) eV or below. The unique point of FDM is that the mass of the particle becomes a unique parameter for calculation. In numerical simulations of FDM halos, we can see the formation of cores in the Hubble time (i.e. the age of the Universe) and relaxations of radial structures. As the test particle mass gets larger, coreformation time becomes longer. One possible caveat for FDM models is the socalled "diversity problem". Our satellite galaxies show diversity in their core structures, while FDM predicts a single scale for core size which is determined by the particle mass. It can be understood by considering nonlinear processes of mergers, the diversity could be generated. Mergers could also be responsible for structures at outer radii, such as the density profile proportional to the inverse cubic of the radius. In order to overcome the numerical difficulties and proceed, GPUaccelerated adaptive mesh code is now being intensively invented. We should see fantastic structures of FDM halos in the near future! Reported by Nagisa Hiroshima

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セミナーレポートQuantum Matter Seminar by Dr. Chang PoYao on February 9, 2023
Please enter the seminar report here!On February 13, 2023, Assistant Professor PoYao Chang of the Department of Physics at National Tsing Hua University in Taiwan gave an online seminar entitled "Entanglement in nonHermitian quantum systems and nonunitary conformal field theories." In the seminar, Professor Chang began by discussing the motivation for studying nonHermitian systems, such as open quantum systems and those with imaginary self energy induced by interaction or disorder. He then introduced the basic concepts of entanglement entropy, arguing that while the quantity is defined through the ground state, it can be used to characterize the entire system similarly to how Boltzmann's thermal entropy characterizes a classical system. In particular, it can be used to characterize topological systems with anyons. Although general nonHermitian systems have complex eigenvalues, he focused on systems that preserve parity and timereversal (PT) symmetry, so that all of the eigenvalues must be real in order to determine the ground state and the entanglement entropy. He showed that in a nonHermitian model, the entropy is negative and corresponds to the negative central charge, which uniquely characterizes conformal field theories (CFTs). As the main result of his recent work, Professor Chang proposed a generic entanglement entropy to characterize nonHermitian systems and showed how it could be used to correctly obtain the entanglement properties of several nonHermitian systems, such as the nonHermitian SuSchriefferHeeger (SSH) model, the qdeformed XXZ model with imaginary boundary terms, and the AffleckKennedyLiebTasaki (AKLT) model, using numerically extracted central charges. In conclusion, Professor Chang's seminar provided valuable insights into the field of entanglement in nonHermitian quantum systems and nonunitary conformal field theories. The seminar was wellreceived by the audience, who appreciated the clarity of the presentation and the relevance of the research topic. Reported by ChenHsuan Hsu (Academia Sinica, Taiwan) and ChingKai Chiu

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セミナーレポートSuper smash problems workshop 3 on January 2527, 2023
From January 25th to 27th, we organized the third Super Smash Problems (SSP) workshop in Kobe. This time we had Kyosuke Adachi (BDR/iTHEMS SPDR) presenting challenging problems he faced in his work. Two main topics were intensively discussed in the workshop. One of them was concerning the generalization of entropyproduction in information thermodynamics. Entropy production can be regarded as a measure of irreversibility of stochastic processes. In other words, irreversibility necessarily comes with positive entropy production. We discussed various systems in biology, physics, and astrophysics that may be relevant to irreversible stochastic systems, like cell growth, formation of phylogenetic trees, machinelearning process, and how universe emerges. Second topic was about phaseseparation. The theory of phaseseparation has a rich mathematical structure: we explored methods with which we can computationally efficiently construct convexhull of a given function. Also, because various systems exhibit phaseseparation, we discussed the potential for which the method can be applied to other systems, including formation of stars. The threeday discussion did not allow us to reach solid conclusion though, we found it very fun and stimulating that mathematics can explain parts of our world that are seemingly totally different. We will continue discussing the problems and hopefully provide you all an update for something resulting. We the organizers sincerely appreciate the audience who attended Adachisan’s introductory lecture and subsequent discussion; and of course, Adachisan for the effort, time, and passion for the SSP workshop. We believe this was a short but very inspiring opportunity. Thank you so much! On behalf, Ryosuke Iritani Reported by Ryosuke Iritani

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セミナーレポートEarly Universe Miniworkshop was held on Jan. 31  Feb. 2, 2023
We held Early Universe Miniworkshop at SUURICOOL (Kobe) on Jan. 31  Feb. 2, 2023. The aim of the workshop was to gather researchers in cosmology and neighboring areas, from students to professors, and discuss future directions towards the understanding of the early Universe and related fundamental issues. In order to stimulate indepth discussions and future collaborations, we organized the workshop in the way that the participants have ample time to interact with each other. Total 22 people attended the workshop on site, as well as over 30 people registered for online participation. The backgrounds of the participants were diverse in terms of nationality, gender and expertise. The topics of the talks at the workshop also range wide, albeit all on the early Universe cosmology in a broad sense, from observational aspects to formal ones. Reported by Ryo Namba
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