77 events in 2024

Seminar
Grassmann Tensor Renormalization Group for twoflavor Schwinger model with a theta term
June 24 (Mon) at 16:00  17:00, 2024
Hayato Kanno (Special Postdoctoral Researcher, Theory Group, RIKEN BNL Research Center, RIKEN Nishina Center for AcceleratorBased Science (RNC))
QCD has been understood through numerical calculations by the Monte Carlo method. However, this method does not work for some parameter regions because of the sign problem. For example, QCD with a theta term has a sign problem, so the nature of QCD with a finite theta parameter is unknown. The theta dependence is also important to axion physics. To reveal such systems, tensor network methods are powerful tools. Tensor network methods have been developed by condensed matter theorists. Furthermore, recently there have been some attempts to apply them to high energy physics. In particular, the tensor renormalization group (TRG) method is remarkable for its applicability to higher dimensions. The Schwinger model is known as a twodimensional toy model of QCD. It has the chiral symmetry and theta term as the same as QCD. In this study, the free energy of the twoflavor Schwinger model is calculated in a broad range of mass and theta parameters. We use TRG to calculate it, with obvious 2pi periodicity of theta parameter. We check the consistency with analytical values in large and small mass limits.
Venue: via Zoom / Seminar Room #359
Event Official Language: English

Lecture
Rigidity and Flexibility of Isometric Embeddings
June 20 (Thu) at 17:00  18:30, 2024
Dominik Inauen (Academic Staff, University of Leipzig, Germany)
The problem of embedding abstract Riemannian manifolds isometrically (i.e. preserving the lengths) into Euclidean space stems from the conceptually fundamental question of whether abstract Riemannian manifolds and submanifolds of Euclidean space are the same. As it turns out, such embeddings have a drastically different behaviour at low regularity (i.e. C^1) than at high regularity (i.e. C^2). For example, by the famous NashKuiper theorem it is possible to find C1 isometric embeddings of the standard 2sphere into arbitrarily small balls in R^3, and yet, in the C^2 category there is (up to translation and rotation) just one isometric embedding, namely the standard inclusion. Analoguous to the Onsager conjecture in fluid dynamics, one might ask if there is a sharp regularity threshold in the Holder scale which distinguishes these flexible and rigid behaviours. In my talk I will review some known results and argue why the Holder exponent 1/2 can be seen as a critical exponent in the problem.
Venue: Graduate School of Mathematical Sciences, The University of Tokyo
Event Official Language: English

Seminar
Finding and understanding diseasecausing genetic mutations
June 20 (Thu) at 16:00  17:00, 2024
Kojima Shohei (Special Postdoctoral Researcher, Genome Immunobiology RIKEN Hakubi Research Team, RIKEN Center for Integrative Medical Sciences (IMS))
Disease is caused by genetic factors and environmental factors. Genomewide association study (GWAS) is a powerful method to find genetic factors associated with disease and human complex traits. One conceptual finding GWAS revealed is that many common diseases are caused by a combination of multiple genetic factors (polygenic), rather than a single causal mutation (monogenic). I have been working on finding genetic factors causing polygenic diseases by developing software that accurately finds sequence insertions and deletions from human populationscale sequencing datasets. In this talk, first, I will introduce some examples of diseasecausing variants we recently discovered. Next I will also introduce my current research theme aiming to untangle how multiple genetic factors coordinately change cellular homeostasis, which I would like to have a collaboration with mathematical scientists.
Venue: Hybrid Format (3F #359 and Zoom), Main Research Building
Event Official Language: English

Seminar
Quantum Computation Study Group Seminars
June 18 (Tue) at 13:30  15:00, 2024
Yuta Kikuchi (Research Scientist, Quantum algorithms and machine learning, Quantinuum K.K.)
Ermal Rrapaj (HPC Architecture and Performance Engineer, National Energy Research Scientific Computing Center (NERSC), Lawrence Berkeley National Laboratory (LBNL), USA)Speaker: Yuta Kikuchi Title: Simulating Floquet scrambling circuits on trappedion quantum computers Abstract: Complex quantum manybody dynamics spread initially localized quantum information across the entire system. Information scrambling refers to such a process, whose simulation is one of the promising applications of quantum computing. We demonstrate the HaydenPreskill recovery protocol and the interferometric protocol for calculating outoftimeordered correlators to study the scrambling property of a onedimensional kickedIsing model on 20qubit trappedion quantum processors. The simulated quantum circuits have a geometrically local structure that exhibits the ballistic growth of entanglement, resulting in the circuit depth being linear in the number of qubits for the entire state to be scrambled. We experimentally confirm the growth of signals in the HaydenPreskill recovery protocol and the decay of outoftimeordered correlators at late times. As an application of the created scrambling circuits, we also experimentally demonstrate the calculation of the microcanonical expectation values of local operators adopting the idea of thermal pure quantum states. Speaker: Ermal Rrapaj Title: Exact block encoding of imaginary time evolution with universal quantum neural networks Abstract: Quantum computers have been widely speculated to offer significant advantages in obtaining the ground state of difficult Hamiltonian in chemistry and physics. The imaginarytime evolution method is a wellknown approach used for obtaining the ground state in quantum manybody problems on a classical computer. In this work we develop a practical method for such purpose. We develop a constructive approach to generate quantum neural networks capable of representing the exact thermal states of all manybody qubit Hamiltonians. The Trotter expansion of the imaginarytime propagator is implemented through an exact block encoding by means of a unitary, restricted Boltzmann machine architecture. Marginalization over the hiddenlayer neurons (auxiliary qubits) creates the nonunitary action on the visible layer. Then, we introduce a unitary deep Boltzmann machine architecture, in which the hiddenlayer qubits are allowed to couple laterally to other hidden qubits. We prove that this wave function ansatz is closed under the action of the imaginarytime propagator and, more generally, can represent the action of a universal set of quantum gate operations. We provide analytic expressions for the coefficients for both architectures, thus enabling exact network representations of thermal states without stochastic optimization of the network parameters. In the limit of large imaginary time, the ansatz yields the ground state of the system. The number of qubits grows linearly with the system size and total imaginary time for a fixed interaction order. Both networks can be readily implemented on quantum hardware via midcircuit measurements of auxiliary qubits. If only one auxiliary qubit is measured and reset, the circuit depth scales linearly with imaginary time and system size, while the width is constant. Alternatively, one can employ a number of auxiliary qubits linearly proportional to the system size, and circuit depth grows linearly with imaginary time only.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English

The speciationlatitude relationship in ferns
June 6 (Thu) at 16:00  17:00, 2024
José Said GutiérrezOrtega (Special Postdoctoral Researcher, iTHEMS)
The latitudinal gradient of diversity (LGD), the pattern that shows that the highest numbers of species in major taxa are at low latitudes and that they decrease towards high latitudes, is the most conspicuous trend on the relationship between geography, environment, and biodiversity. But there is not a concrete answer of why it exists. Three hypotheses have been proposed so far: 1) tropics contain more species because communities have been climatically stable for longer time than the temperate areas; 2) the tropics receives more energy, which allows groups to diversify at higher rates; 3) the tropics provide a higher diversity of ecological opportunities for new species to specialize. By analyzing the fern community from the American continent, I tested the three hypotheses, and found that the first hypothesis is the most likely. The tropics contain more species not because they produce more species than the temperate areas, but because extinction has been lower historically. These results suggest that the climatic instability (cycles of interglaciationglaciation) at high latitudes have shaped this curious pattern. I am using this seminar to show you some of my research progress, and to briefly mention some of the problems that I have encounter while trying to test my hypotheses. Maybe we can make some ideas to improve the methodological aspects of this kind of macroecological research
Venue: via Zoom
Event Official Language: English

Workshop
Recent Developments and Challenges in Topological Phases
June 3 (Mon)  14 (Fri), 2024
Thanks to intensive research efforts, topology has been established as a fundamental concept in physics. For closed quantum systems, the classification of gapped topological phases has matured. Moreover, the importance of topology is not limited to isolated quantum systems. Recently, the topology of nonHermitian Hamiltonians, which effectively describe systems with dissipation, has attracted much attention worldwide. This fascination is exemplified by topological phases and topological phenomena unique to nonHermitian systems. Against this background, the primary purpose of this workshop is to bring together researchers working on topological phases and to discuss (i) open questions in topological phases of closed quantum systems and (ii) the role of topology in open quantum systems and measurements.
Venue: Yukawa Institute for Theoretical Physics, Kyoto University
Event Official Language: English

On the volume conjecture for the Teichm ̈uller TQFT
May 31 (Fri) at 15:00  17:00, 2024
Soichiro Uemura (Junior Research Associate, iTHEMS / Student Trainee, iTHEMS)
The ChernSimons theory is a topological quantum field theory (TQFT) on the principal Gbundle and has been studied in both mathematics and physics. When G is SU(2), which is compact, Witten conjectured that its path integral gives the topological invariant of the base 3manifold. This invariant was formulated rigorously and is known as the WRT invariant. In addition, it is known that the expectation value of the Wilson loop along the hyperbolic knot in S3 gives the invariant of knots, which is called the colored Jones polynomial. Invariants of knots and manifolds derived from the path integral are called quantum invariants. There is an open conjecture called the volume conjecture, which states that the complete hyperbolic volume of the knot complement appears in the asymptotic expansion of the colored Jones polynomial. The volume conjecture suggests a close connection between quantum invariants and hyperbolic geometry. On the other hand, ChernSimons theory with the noncompact G such as SL(2,C) also appears in duality in string theory called the 3d3d correspondence but has not been well formulated mathematically. Andersen and Kashaev constructed a TQFTlike theory called the Teichm ̈uller TQFT by quantizing the Teichm ̈uller space, which is the deformation space of the hyperbolic structures on a surface. The Teichm ̈uller TQFT is expected to correspond to the SL(2,C) ChernSimons theory. In this theory, a conjecture similar to the volume conjecture has been proposed and proven for several hyperbolic knots. In this talk, I will introduce the outline of the Teichm ̈uller TQFT and explain our results on the volume conjecture and its proof using techniques in hyperbolic geometry by Thurston, Casson, Rivin, and others.
Venue: via Zoom / Seminar Room #359
Event Official Language: English

Seminar
Lipid Peroxidation Structure Selectivity: A Clue to Coal Workers' Pneumoconiosis
May 30 (Thu) at 16:00  17:00, 2024
Cai Tie (Associate Professor, China University of Mining and Technology, China)
Coal workers' pneumoconiosis (CWP), resulting from the inhalation of coal dust mixtures, is one of the leading occupational diseases globally. Despite its seriousness, there is still no effective curative method available for CWP. Therefore, a systemic understanding of CWP's pathogenesis is urgently needed. Peroxidation is an oxidation chain reaction in which lipids (glycerophospholipids and other membrane lipids) are degraded into excretory forms, such as fatty aldehydes. This process involves a series of enzymes that catalyze the reactions leading to lipid degradation. Our previous work identified specific regulatory mechanisms in lipid peroxidation processes triggered by diseases or various interventions. To gain a comprehensive understanding of lipid peroxidation, we developed a systematic profiling strategy that allows for the detailed observation of these oxidative processes. Additionally, we adapted this profiling strategy to investigate risk factors associated with coal workers' pneumoconiosis (CWP). By applying our methods to the study of CWP, we aimed to uncover the metabolic and molecular changes induced by coal dust inhalation, providing insights that could contribute to better prevention and treatment strategies for this occupational disease. To comprehensively investigate the lung alterations associated with CWP, both a cohort of coal miners and a CWP rat model were studied. Through the analysis of lipid peroxidation alterations associated with CWP occurrence, several CYP subtypespecific metabolic processes were identified. These findings suggest that coalderived polycyclic aromatic hydrocarbons (PAHs) are major risk factors for CWP due to the specific activation of the Aryl Hydrocarbon Receptor (AhR) pathway. Further evidence at the gene level and morphological changes supports the role of coalderived PAHs as key factors in the development of CWP. Hence, it is crucial to consider the toxicity induced by PAHs in the prevention and treatment of CWP.
Venue: via Zoom
Event Official Language: English

The New World of Spin Zero  Some Novel Approaches at QUP for Experimental Particle Cosmology 
May 28 (Tue) at 13:30  15:00, 2024
Masashi Hazumi (Director, Professor, International Center for Quantumfield Measurement Systems for Studies of the Universe and Particles (QUP), High Energy Accelerator Research Organization (KEK))
Particle cosmology is a discipline seeking a fundamental understanding of the Universe based on particle physics. Five mysteries drive our research today: cosmic inflation, baryon asymmetry, neutrino properties, dark matter, and dark energy. Resolving any of the five mysteries will revolutionize our picture of the Universe. Numerous interesting theoretical hypotheses have been proposed to this end. Many require new scalar quantum fields, such as inflatons, axions, supersymmetric particles, etc. They are, in a sense, an attempt to expand the role of the vacuum. Since we have not found such spinzero fields yet, we shall invent new eyes to make an experimental or observational breakthrough. The International Center for Quantumfield Measurement Systems for Studies of the Universe and Particles (QUP) was established in December 2021 at KEK under the WPI program of MEXT and JSPS. With its tagline of "bring new eyes to humanity," one of the primary missions of QUP is inventing and developing such new eyes for particle cosmology. In this seminar, after briefly introducing QUP, I focus on research topics I have contributed, including the LiteBIRD satellite to study inflatons and light scalar quantum field searches with novel methods using quantum sensing techniques.
Venue: Okochi Hall / via Zoom
Event Official Language: English

Introduction to homotopy theory
May 24 (Fri) at 15:00  17:00, 2024
Junnosuke Koizumi (Special Postdoctoral Researcher, iTHEMS)
In a narrow sense, homotopy theory is a framework for capturing the essential structures of shapes and has long been used as a powerful tool in topology. On the other hand, the concept of homotopy is so universal that it appears even in purely algebraic settings and has recently had a significant impact on other fields such as number theory and algebraic geometry. This talk aims to introduce homotopy theory in this broader sense from multiple perspectives. If time permits, I will also touch upon recent developments in the homotopy theory of algebraic varieties.
Venue: via Zoom / Seminar Room #359
Event Official Language: English

The collective order of human corneal endothelial cells as a unified biomarker for in vitro cultured cells and in vivo regenerated tissue
May 23 (Thu) at 16:00  17:00, 2024
Akihisa Yamamoto (Research Scientist, iTHEMS)
Approximately 200,000 corneal transplantations are performed worldwide yearly, and more than half of them are applied to patients with corneal endothelial dysfunction. Recently, the restoration of functional corneas by injecting cultureexpanded cells has developed in contrast to the conventional transplantation which relies on a limited number of donors’ corneas. This novel treatment opens up the potential to cure more patients with less surgical invasion and allows the utilization of cells with consistent and controlled quality. In this talk, I will introduce a unified physical biomarker for the quality assessment of corneal endothelial cells in in vitro culture and the predictive diagnosis of in vivo tissues using a single equation based on the collective order of cells. Taking an analogy to the twodimensional colloidal assembly, the spatial arrangement of cells is generalized in terms of manybody interactions, and the “spring constant” of the underlying interaction potential is calculated from microscopy images. I also would like to discuss our recent approach to characterize the local structure of the arrangement of cells based on the topological data analysis.
Venue: via Zoom
Event Official Language: English

Seminar
Prefactorization algebra and theta term
May 21 (Tue) at 16:00  17:30, 2024
Masashi Kawahira (Ph.D. Student, Yukawa Institute for Theoretical Physics, Kyoto University)
Quantum field theories (QFTs) describe a lot of physical phenomena in our world. And giving a mathematical definition of QFTs is a longstanding problem. There are several mathematical formulations: Wightman formulation, Osterwalder–Schrader formulation and AtiyahSegal formulation. And each of them cover different aspects of QFTs. Recently, Costello and their collabolators formulate QFTs by using prefactorization algbras. This formulaion cover a lot of classes of QFTs: TQFTs, 2d CFTs and perturbative QFTs. And they reproduce various results such as asymptotic freedom in nonAbelian gauge theories. Prefactorization algbras can be given by Batalin–Vilkovisky quantization (BV quantization) of the Lagrangian. However the original BV quantizations are perturbative and they do not have nonperturbative effects like instantons. In this talk, we propose the way to include Abelianinstanton effects. In modern language, it is the same as ℤgauging.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Workshop
iTHEMSYITP Workshop: Bootstrap, Localization and Holography
May 20 (Mon)  24 (Fri), 2024
Venue: Yukawa Institute for Theoretical Physics, Kyoto University
Event Official Language: English

Introduction to operator algebras
May 17 (Fri) at 15:00  17:00, 2024
Kan Kitamura (Special Postdoctoral Researcher, iTHEMS)
I will give a quick introduction to operator algebras. Operator algebras in this talk consist of linear operators over some Hilbert space. Their study was initiated by Murray and von Neumann, motivated partially by the mathematical foundation of quantum mechanics. Starting from the definitions of a few basic notions, I will explain that commutative operator algebras can be interpreted as spaces. On the other hand, simple operator algebras (i.e., those without nontrivial ideals) form a class of operator algebras opposite to commutative ones and have attracted many operator algebraists. I will try to introduce several examples of simple operator algebras, some of which appear in mathematical physics. If time permits, I will also give recent results on ideals in C*algebras. People with any scientific background are welcome.
Venue: via Zoom / Seminar Room #359
Event Official Language: English

Seminar
Exploring the impact of environments on flower color differentiation: A metaanalytical approach
May 16 (Thu) at 16:00  17:00, 2024
Masaru Bamba (Assistant Professor, Graduate School of Science, Tohoku University)
Flower color is one of the most diverse phenotypes in angiosperms, yet the initial processes of its differentiation remain unclear. Flower color is primarily expressed through the accumulation of pigment compounds in the petals, which are also associated with various stress responses. While it is conceivable that the environmental conditions during plant evolution could contribute to the differentiation of flower color, few studies have examined this hypothesis. Therefore, I conducted a metaanalysis using plant flower color information and growth environment data to elucidate the relationship between flower color differentiation and growth environments. Flower color data was extracted using LLM from botanical descriptions, and growth environment data was acquired by aligning GBIF occurrence information with WorldClim and ISRIC databases. Integrating approximately 30,000 flower color data points and 35 million occurrence records revealed trends such as a predominance of red flowers at higher altitudes and white flowers in arid areas. This study is still preliminary, so I would welcome discussions on more suitable analytical methods and models.
Venue: via Zoom
Event Official Language: English

Seminar
Black hole graviton and quantum gravity
May 16 (Thu) at 15:00  16:30, 2024
Yusuke Kimura (Research Scientist, Analytical quantum complexity RIKEN Hakubi Research Team, RIKEN Center for Quantum Computing (RQC))
Drawing from a thought experiment that we conduct, we propose that a virtual graviton gives rise to a black hole geometry when its momentum surpasses a certain threshold value on the Planck scale. This hypothesis implies that the propagator of a virtual graviton, that possesses momentum surpassing this threshold, vanishes. Consequently, a Feynman diagram containing this type of graviton propagator does not add to the overall amplitude. This mechanism suggests the feasibility of formulating an ultravioletfinite fourdimensional quantum gravitational theory. The elementary particles including the gravitons are treated as point particles in this formulation.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Seminar
Boundaryinduced transitions in Möbius quenches of holographic BCFT
May 15 (Wed) at 16:00  17:30, 2024
Dongsheng Ge (Project Researcher, Department of physics, Osaka University)
Boundary effects play an interesting role in finitesize physical systems. In this work, we study the boundaryinduced properties of 1+1dimensional critical systems driven by inhomogeneous Möbiuslike quenches. We focus on the entanglement entropy in BCFTs with a large central charge and a sparse spectrum of lowdimensional operators. We find that the choice of boundary conditions leads to different scenarios of dynamical phase transitions. We also derive these results in a holographic description in terms of intersecting branes in AdS3, and find a precise match.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English

Workshop
iTHEMS Cosmology Forum 1  Cosmic Birefringence and Parity Violation in the Universe
May 14 (Tue) at 9:30  18:00, 2024
Toshiya Namikawa (Project Assistant Professor, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo)
Maresuke Shiraishi (Associate Professor, Suwa University of Science)
Fuminobu Takahashi (Professor, Department of Physics, Graduate School of Science, Tohoku University)iTHEMS Cosmology Forum Workshop is a series of short workshops, each focused on an emerging topics in cosmology. The targeted audience is cosmologists, highenergy physicists and astronomers interested in learning about the subject, not just those who have already worked on the topic. The goal of the workshop is to provide working knowledge of the topic and leave dedicated time for discussions to encourage mutual interactions among participants. The first workshop is devoted to cosmic birefringence, a newly establishing cosmological probe of the nature of our universe. Cosmic birefringence is the rotation of the linear polarization plane of the cosmic microwave background (CMB) radiation and, thanks to its origin, inherently measures the degree of parity violation in the cosmic history. This oneday workshop gathers both the observational and theoretical aspects of this growing topic. The workshop will be in English. The venue is on RIKEN Wako Campus, and the exact room is yet to be determined, depending on the number of registered participants. The workshops are organised by the iTHEMS Cosmology Forum working group, which is the successor of the Dark Matter Working Group at RIKEN iTHEMS. Important dates: 30th April  Registration deadline 14th May  Workshop Day Invited Speakers: Toshiya Namikawa (Kavli IPMU) Maresuke Shiraishi (Suwa University of Science) Fuminobu Takahashi (Tohoku University) Organisers: Kohei Hayashi, Nagisa Hiroshima, Derek Inman, Amaury Micheli, Ryo Namba
Venue: #435437, 4F, Main Research Building
Event Official Language: English

Workshop
Nuclear Fusion and its Interdisciplinary Fields
May 14 (Tue) at 9:00  18:15, 2024
We will learn about nuclear fusion and related subjects, such as turbulence in astronomy and astrophysics, from experts and discuss possible interdisciplinary collaborations in the near future. Some researchers will visit RIKEN iTHEMS from the National Institute for Fusion Science (NIFS) and other universities and research institutes for the workshop. We will have the workshop in a hybrid style so that many researchers in Japan can hear the presentations even remotely. This workshop is supported by Moonshot Goal 10 (Program Director Yoshida Zensho (NIFS)). Program Session１ 9:009:35 (25+10: 25 mins for Presentation, 10 mins for Q&A)：Shinya Maeyama 9:3510:10 (25+10): Naoki Sato 10:1010:45 (25+10): Yohei Kawazura 10:4511:15 Coffee Break Session２ 11:1511:50 (25+10): Takanobu Amano 11:5012:25 (25+10): Yosuke Matsumoto 12:2513:00 (25+10): Akira Mizuta 13:0014:00 Lunch Break Session３ 14:0014:35 (25+10): Chiho Nonaka 14:3515:10 (25+10): Takeo Hoshi 15:1015:45 (25+10): Motoki Nakata 15:4516:15 Coffee Break Session ４ 16:1516:50 (25+10): Kumiko Hori 16:5017:25 (25+10): Yutaka Ohira 17:2518:00 (25+10): Camilia Demidem (TBC) 18:3020:30: Dinner in the Main Research Building.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
77 events in 2024
Events
Categories
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 iTHEMS Colloquium
 MACS Colloquium
 iTHEMS Seminar
 iTHEMS Math Seminar
 DMWG Seminar
 iTHEMS Biology Seminar
 iTHEMS Theoretical Physics Seminar
 Information Theory SG Seminar
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 ABBLiTHEMS Joint Astro Seminar
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 Theory of Operator Algebras
 iTHEMS Intensive CourseEvolution of Cooperation
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 Knot Theory
 iTHES Theoretical Science Colloquium
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 iTHES Seminar