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 Nash--Kuiper theorem it is possible to find C1 isometric embeddings of the standard 2-sphere 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

Finding and understanding disease-causing 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. Genome-wide 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 population-scale sequencing datasets. In this talk, first, I will introduce some examples of disease-causing 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

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 trapped-ion quantum computers Abstract: Complex quantum many-body 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 Hayden-Preskill recovery protocol and the interferometric protocol for calculating out-of-time-ordered correlators to study the scrambling property of a one-dimensional kicked-Ising model on 20-qubit trapped-ion 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 Hayden-Preskill recovery protocol and the decay of out-of-time-ordered 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 imaginary-time evolution method is a well-known approach used for obtaining the ground state in quantum many-body 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 many-body qubit Hamiltonians. The Trotter expansion of the imaginary-time propagator is implemented through an exact block encoding by means of a unitary, restricted Boltzmann machine architecture. Marginalization over the hidden-layer neurons (auxiliary qubits) creates the non-unitary action on the visible layer. Then, we introduce a unitary deep Boltzmann machine architecture, in which the hidden-layer qubits are allowed to couple laterally to other hidden qubits. We prove that this wave function ansatz is closed under the action of the imaginary-time 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 mid-circuit 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

Advances in Fluctuating Hydrodynamics: Bridging the Micro and Macro Scales

June 17 (Mon) - 28 (Fri), 2024

Abhishek Dhar (Professor, International Centre for Theoretical Sciences, India)
Luca Delacrétaz (Assistant Professor, The University of Chicago, USA)
Tomohiro Tanogami (Assistant Professor, Department of Earth and Space Science, Graduate School of Science, Osaka University)
Taiki Haga (Assistant Professor, Division of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University)
Yukinao Akamatsu (Assistant Professor, Department of Physics, Graduate School of Science, Osaka University)
Keisuke Fujii (JSPS Research Fellow PD, Department of Physics, Graduate School of Science, The University of Tokyo)
Harukuni Ikeda (Assistant Professor, Department of Physics, Faculty of Science, Gakushuin University)
Yuki Minami (Assistant Professor, Graduate School of Engineering, Gifu University)
Hiroyoshi Nakano (Assistant Professor, The Institute for Solid State Physics (ISSP), The University of Tokyo)
Yusuke Nishida (Professor, Department of Physics, Tokyo Institute of Technology)
Makiko Sasada (Professor, Graduate School of Mathematical Sciences, The University of Tokyo)

Establishing universal laws in far-from-equilibrium physical systems is one of the outstanding unresolved problems in modern physics. While we have not reached a complete theory applicable to any nonequilibrium system, hydrodynamics provides a promising theoretical tool, which captures universal macroscopic behaviors of nonequilibrium many-body systems. In particular, a hydrodynamic approach with thermal fluctuation, dubbed fluctuating hydrodynamics, successfully describes normal hydrodynamic transports in three-dimensional systems as well as anomalous transports (related to the Kardar–Parisi–Zhang universality class) in low-dimensional systems. The purpose of this workshop is to bring together theorists working on both classical and quantum many-body problems and to explore nonequilibrium physics from the viewpoint of fluctuating hydrodynamics.

Venue: Panasonic Hall, Yukawa Institute for Theoretical Physics, Kyoto University (Main Venue) / via Zoom

Event Official Language: English

The speciation-latitude relationship in ferns

June 6 (Thu) at 16:00 - 17:00, 2024

José Said Gutiérrez-Ortega (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 interglaciation-glaciation) 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 macro-ecological research

Venue: via Zoom

Event Official Language: English

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 non-Hermitian Hamiltonians, which effectively describe systems with dissipation, has attracted much attention worldwide. This fascination is exemplified by topological phases and topological phenomena unique to non-Hermitian 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 Chern-Simons theory is a topological quantum field theory (TQFT) on the principal G-bundle 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 3-manifold. 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, Chern-Simons theory with the non-compact G such as SL(2,C) also appears in duality in string theory called the 3d-3d correspondence but has not been well formulated mathematically. Andersen and Kashaev constructed a TQFT-like 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) Chern-Simons 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

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 subtype-specific metabolic processes were identified. These findings suggest that coal-derived 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 coal-derived 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 Quantum-field 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 spin-zero fields yet, we shall invent new eyes to make an experimental or observational breakthrough. The International Center for Quantum-field 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 culture-expanded 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 two-dimensional colloidal assembly, the spatial arrangement of cells is generalized in terms of many-body 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

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 long-standing problem. There are several mathematical formulations: Wightman formulation, Osterwalder–Schrader formulation and Atiyah-Segal 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 non-Abelian 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 non-perturbative effects like instantons. In this talk, we propose the way to include Abelian-instanton effects. In modern language, it is the same as ℤgauging.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

iTHEMS-YITP 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 non-trivial 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

Exploring the impact of environments on flower color differentiation: A meta-analytical 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 meta-analysis 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

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 ultraviolet-finite four-dimensional 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

Boundary-induced 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 finite-size physical systems. In this work, we study the boundary-induced properties of 1+1-dimensional critical systems driven by inhomogeneous Möbius-like quenches. We focus on the entanglement entropy in BCFTs with a large central charge and a sparse spectrum of low-dimensional 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

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, high-energy 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 one-day 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: #435-437, 4F, Main Research Building

Event Official Language: English

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 9:00-9:35 (25+10: 25 mins for Presentation, 10 mins for Q&A)：Shinya Maeyama 9:35-10:10 (25+10): Naoki Sato 10:10-10:45 (25+10): Yohei Kawazura 10:45-11:15 Coffee Break Session２ 11:15-11:50 (25+10): Takanobu Amano 11:50-12:25 (25+10): Yosuke Matsumoto 12:25-13:00 (25+10): Akira Mizuta 13:00-14:00 Lunch Break Session３ 14:00-14:35 (25+10): Chiho Nonaka 14:35-15:10 (25+10): Takeo Hoshi 15:10-15:45 (25+10): Motoki Nakata 15:45-16:15 Coffee Break Session ４ 16:15-16:50 (25+10): Kumiko Hori 16:50-17:25 (25+10): Yutaka Ohira 17:25-18:00 (25+10): Camilia Demidem (TBC) 18:30-20:30: Dinner in the Main Research Building.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English