Seminar
1013 events
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Seminar
A New Holographic Entanglement Entropy in the de Sitter space
June 13 (Fri) 16:00 - 17:00, 2025
Yuki Suzuki (Ph.D. Student, Yukawa Institute for Theoretical Physics, Kyoto University)
We propose a new holographic entanglement entropy in the three-dimensional de Sitter space. It is known that the holographic entanglement entropy via Ryu-Takayanagi prescription violates the entropic inequalities that they should satisfy. We propose a kind of extensions of the Ryu-Takayanagi formula so that they satisfy the strong subadditivity. We fix consistent parameter regions of the entropy and finally comment on the implications to the static patch holography.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
From Galaxies to Cosmological Structures: The Multi-Scale Influence of Cosmic Rays
June 13 (Fri) 14:00 - 15:15, 2025
Ellis Owen (Special Postdoctoral Researcher, Astrophysical Big Bang Laboratory, RIKEN Pioneering Research Institute (PRI))
Cosmic rays interact with astrophysical systems over a broad range of scales. They go hand-in-hand with violent, energetic astrophysical environments, and are an active agent able to regulate the evolution and physical conditions of galactic and circum-galactic ecosystems. Depending on their energy, cosmic rays can also escape from their galactic environments of origin, and propagate into larger-scale cosmological structures. In this talk, I will discuss the impacts of cosmic rays retained in galaxies. I will show they can deposit energy and momentum to alter the initial conditions of star-formation, modify the circulation of baryons around galaxies, and have the potential to regulate long-term galaxy evolution. I will highlight some of the astrophysical consequences of contained hadronic and leptonic cosmic rays in and around galaxies, and how their influence can be probed using signatures including X-rays, gamma-rays and neutrinos. I will also discuss what happens to the cosmic rays that escape from galaxies, including their interactions with the magnetized large-scale structures of our Universe, and the fate of distant high-energy cosmic rays that do not reach us on Earth.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Gravitational Lensing in the Schwarzschild Spacetime: Photon Rings in Vacuum and in the Presence of a Plasma
June 12 (Thu) 15:00 - 16:30, 2025
Torben Christian Frost (Postdoctoral Researcher, Kavli Institute for Astronomy and Astrophysics, Peking University, China)
Astrophysical black hole candidates are often surrounded by an accretion disk. In particular the interior region of this accretion disk can consist of a plasma and the trajectories of light rays travelling through this plasma can deviate significantly from the trajectories of light rays travelling through vacuum. While usually these environments are very complex we can already learn a lot about the observable features using simple plasma models. In the context of general relativity for some of these plasma models the equations of motion are fully separable and even analytically solvable. In my talk I will illustrate what we can learn from such models using the Schwarzschild spacetime as background. I will assume that the black hole is surrounded by an inhomogeneous, pressureless, and non-magnetised plasma and solve the equations of motion analytically exact. Then I will assume that we have a luminous disk in the equatorial plane and discuss the impact of the plasma on the so-called photon rings. I will discuss the changes of their geometrical structure, the redshift, and the travel time of the photons compared to photon rings in vacuum and what we can learn about the properties of the plasma. I will also discuss how the presence of the plasma may be able to help us to constrain gravity in the strong field regime. Finally, I will discuss how the obtained results will contribute to designing a multimessenger approach for probing gravity in the strong field regime in the context of the Maxwell-Einstein-Pauli Observatory.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
Inferring Castration Status and Age-at-Death from Sheepskin Parchments
June 12 (Thu) 13:00 - 14:00, 2025
Ciarán O'Connor (Ph.D. Student, Department of Genetics, Trinity College Dublin, Ireland)
Secondary products such as traction from cattle, wool from sheep, and mobility from horses are invaluable outputs from rearing livestock. The innovative herd management practice of castration enables non-breeding males to be managed safely beyond typical ages of slaughter, greatly improving the productivity of livestock herds. Although osteological methods can identify some morphological differences between castrated and intact males, it is difficult to make clear distinctions between them. However, methylation values are affected by the considerable hormonal changes that occur as a result of castration. For example, castrated male sheep have shown lower biological ages compared to age-matched intact rams (Sugrue et al., 2021). Furthermore, age-at-death has been predicted from reconstructed methylation values in ancient horses, informing on culling practices (Liu et al., 2023). Using an aDNA-specific bisulfite sequencing approach, we have reconstructed CpG methylation values from sheepskin parchments. We have developed machine learning models trained on modern sheep in order to infer traits of interest such as castration and age-at-death. The informative CpG sites have been incorporated into a target capture set to enable cost-effective sequencing of additional samples. This will enable the characterisation of these traits in ancient sheep across time periods, geographical locations, and archaeological contexts.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Collective Behaviors and Deep Learning Applications
June 11 (Wed) 15:00 - 16:00, 2025
Lingxiao Wang (Research Scientist, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))
Understanding and modeling collective pedestrian behavior, particularly under extreme conditions, is a challenging problem that combines cognition, physics, and data analysis. In the second talk of DEEP-IN series, I will explore how deep learning can reveal the underlying principles of crowd dynamics from data. Starting with a bounded rationality framework, we demonstrate how deep learning can quantify evacuation dynamics and reveal hidden patterns in collective motion. Specifically, we demonstrate how macroscopic observables, such as entropy and kinetic energy, can be extracted from microscopic trajectories in simulations and real-world data. This is an informal seminar, we will start with the methodology and some practical examples, and finally reserve time for everyone interested to discuss it together.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
A New Measure of Genuine Multipartite Entanglement
June 6 (Fri) 14:00 - 15:00, 2025
Jaydeep Kumar Basak (Post-doctoral Fellow, Gwangju Institute of Science and Technology (GIST), Republic of Korea)
In this talk, I will introduce ``Latent entropy" (L-entropy) as a novel measure to characterize genuine multipartite entanglement in pure states, applicable to quantum systems with both finite and infinite degrees of freedom. This measure, derived from an upper bound on reflected entropy, attains its maximum for three-party GHZ states and $n=4,5$-party $2$-uniform states. I will also show the generalization of this measure for higher party states. Furthermore, I will discuss an analogue of the Page curve in multiboundary wormholes. If time permits, I will show the behaviour of multipartite entanglement in random states.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Exotic Pairing Nature and Charge Ordering in Kagome Superconductor
June 5 (Thu) 15:00 - 16:15, 2025
Wu Xianxin (Associate Professor, CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China)
Abstract：Recent experimental investigations have identified fascinating electronic orders in kagome metals, such as intriguing superconductivity, charge density wave (CDW) and nematicity. Notably, there is various evidence of spontaneous time-reversal symmetry (TRS) breaking within the CDW phase, pointing to a long-pursued loop current order, though its underlying mechanism remains elusive. In this talk, I will first review the exotic properties of these kagome superconductors. Then, I will discuss the effective model and the unique sublattice texture associated with van Hove singularities in the kagome lattice [1], which turns out to have significant effect on correlated states. Finally, I will present our scenario for realizing a TRS breaking CDW within the kagome lattice and discuss loop-current fluctuation induced unconventional pairing [2-4]. Potential experimental implications will be also discussed.
Venue: via Zoom / #359, Main Research Building
Event Official Language: English
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Seminar
Solving Inverse Problems with Physics-Driven Deep Learning
June 4 (Wed) 15:00 - 16:00, 2025
Lingxiao Wang (Research Scientist, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))
This talk kicks off a four-part seminar series on the DEEP-IN WG, an interdisciplinary working group exploring how modern deep learning — including deep generative models — can tackle inverse problems across scientific domains. In addition to DEEP-IN activities, I will present a new framework and vision, motivated by the growing synergy between physics-driven designs for deep learning and scientific discovery, as discussed in our recent review article. Future talks will demonstrate machine learning applications in collective behaviors, weather systems, and lattice field simulations. This is an informal seminar, we will start with the methodology, give some practical examples, and finally reserve time for everyone interested to discuss it together.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
Extracting particle mass on quantum computers: state preparation and measurement
June 3 (Tue) 11:00 - 12:30, 2025
Xiaoyang Wang (Postdoctoral Researcher, Quantum Mathematical Science Team, Division of Applied Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))
In this seminar, I will introduce the procedure of extracting particle mass from the ab initio calculation using quantum computers, including two essential steps: state preparation and measurement. For the measurement process, in our recent work "Computing n-time correlation functions without ancilla qubits" [arXiv:2504.12975], we developed a measurement method for correlation functions without ancilla qubits, circumventing longstanding hardware constraints of limited qubit connectivity and short-range control operations. We demonstrate our method using IBM quantum hardware and successfully reproduce the noiseless results of the Schwinger model hadron mass within a relative error of 0.18%, even in the presence of realistic hardware limitations and noise. For the state preparation process, another work "Performance guarantees of light-cone variational quantum algorithms for the maximum cut problem" [arXiv:2504.12896] focused on the accuracy of the state preparation using variational quantum algorithms (VQAs). We propose a light-cone VQA with provable performance guarantees, whose single round has higher accuracy than the 3-round standard VQA for the maximum cut problem. We experimentally validated the single-round light-cone VQA using IBM quantum hardware with solution accuracy that exceeds the known classical hardness threshold in both a 72-qubit demonstration and a 148-qubit demonstration.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
Ecology and Evolution of Mammal-Microbe Interactions
May 29 (Thu) 16:00 - 17:00, 2025
Taichi A Suzuki (Assistant Professor, Biodesign Center for Health Through Microbiomes, Arizona State University, USA)
A critical open question in microbiome research is identifying key host-microbial interactions that influence host fitness. While the disruption of coevolved host-microbial interactions is known to affect host fitness in simpler systems (e.g., insects and their symbionts), understanding the extent and consequences of host-microbial coevolution in more complex systems (e.g., mammals and their gut microbiota) remains a major challenge. My research has identified multiple species of gut microbes in adults and children that share a parallel evolutionary history with humans by analyzing paired human genotypes and bacterial strain genotypes. In another line of work, I applied a selection experiment demonstrating that selection and transmission of the microbiome and its metabolites can alter mouse locomotion behavior within four rounds of microbiome transfer, without any changes to the mouse genome. Finally, I will briefly outline my future plans to study the effects of disrupting evolutionary stable host-microbial associations on the phenotypes of deer mice (Peromyscus spp.) in the Madrean Sky Islands and genetically diverse human populations in Arizona. Biosketch: Assistant Professor at Arizona State University since 2023. MS at University of Arizona, PhD at University of California Berkeley, and Postdoc at Max Planck Institute for Biology. My group integrates evolutionary genomics, microbial ecology, and biomedical research to study host-microbial interactions using wild rodents and humans.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
Non-perturbative formulation of resonant quantum mechanics within unified exact WKB framework
May 28 (Wed) 16:00 - 17:30, 2025
Okuto Morikawa (Special Postdoctoral Researcher, Division of Fundamental Mathematical Science, RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS))
We study quasi-stationary states in quantum mechanics using the exact WKB analysis as a non-perturbative framework. We explore unstable states such as resonances by analyzing the inverted Rosen-Morse potential, which exhibits barrier resonance. This model allows exact solutions, enabling a direct comparison with exact WKB predictions. We provide a simple analytic picture of resonance and demonstrate consistency between exact and WKB-based results. A unified exact WKB framework is developed for exploring the equivalence and complementarity of different well-established regularizations \`a la Zel'dovich, complex scaling, and rigged Hilbert space within this framework.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Generalized symmetry from Type IIB superstring theory
May 27 (Tue) 16:00 - 17:00, 2025
Masashi Kawahira (Postdoctoral Fellow, Department of Physics, Graduate School of Science, Kobe University)
Recently, generalized symmetries have enabled the systematic analysis of various quantum systems. In this talk, we focus on global generalized symmetries that appear in the low-energy effective theory of type IIB superstring theory (i.e., type IIB supergravity). Specifically, we highlight the SL(2,ℤ) gauge symmetry (self-duality) in type IIB supergravity. We see that a global ℤ₁₂ eight-form symmetry arises as the quantum symmetry of the SL(2,ℤ) gauge symmetry. And we discuss its topological operator and its relation to 7-branes. This talk is based on joint work with Hiroki Wada (Tohoku University) and Naoto Kan (Osaka University).
Venue: Hybrid Format (3F #359 and Zoom), Main Research Building (Main Venue) / via Zoom
Event Official Language: English
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Seminar
A review of incompatibility in quantum information science (Topical Review Meeting #1)
May 26 (Mon) 16:00 - 17:30, 2025
Haruki Emori (Ph.D. Student, Graduate School of Information Science and Technology, Hokkaido University)
As the first activity of the Quantum Foundation Study Group, we will hold a Topical Review Meeting. In quantum mechanics and quantum information science, the exploration of “quantumness” is of fundamental importance. One key concept that captures quantumness is “incompatibility”. In this meeting, I will give a review on incompatibility. If time permits, I would also like to introduce some of my recent research on this topic and engage in discussions with the participants.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
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Seminar
SISSI: Supernovae in a Shearing, Stratified Interstellar Medium
May 23 (Fri) 14:00 - 15:15, 2025
Leonard Romano (Ph.D. Student, Ludwig-Maximilians-Universität München, Germany)
Supernovae (SNe) are an important driver of the multiphase structure in the Interstellar Medium (ISM) and play an important role for regulating star formation. SNe inflate large bubbles of hot gas dubbed Supernova Remnants (SNRs) that can remain hot for several 10⁵-10⁶ years, contributing substantially to the volume filling hot phase, galactic outflows and the driving of turbulence in the ISM. In this talk, I am presenting the results of zoom-in simulations of SNRs embedded in a simulated isolated Milky-Way analogue, in order to investigate how environmental effects like shear, vertical stratification and a self-consistently generated ISM can affect various properties of SNRs. I find that initially microscopic SNRs, whose dynamics are dominated by local shock physics, after a few Myr enter a mesoscopic regime, where their dynamics are increasingly dominated by galactic scale processes. Based on these findings, I make predictions about SN-driven large-scale structure, such as galactic outflows and the geometry of large superbubbles in disk galaxies.
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Beyond-classical simulations using a quantum annealer
May 23 (Fri) 10:00 - 11:15, 2025
Alberto Nocera (Senior Staff Scientist, Stewart Blusson Quantum Matter Institute, The University of British Columbia, Canada)
Join us for an electrifying online zoom talk featuring Dr. Alberto Nocera, the author of the groundbreaking Science article detailing D-Wave's quantum annealer outperforming classical supercomputers in simulating complex magnetic materials. D-Wave’s quantum annealer uses quantum annealing to efficiently solve optimization problems by finding low-energy states of complex systems. Unlike IBM and Quantinuum’s gate-based quantum computers, which are universal and execute algorithms via quantum circuits, D-Wave’s system is specialized but currently more scalable and practical for certain applications. While gate-based systems are still limited by noise and error rates, D-Wave’s annealer recently demonstrated a quantum advantage in simulating magnetic materials, outperforming classical supercomputers. This highlights a key difference: D-Wave excels in specific tasks today, while IBM and Quantinuum aim for broader, long-term quantum computational capabilities. Talk Abstract: Solving the equations governing the dynamics of interacting many-particle quantum systems is one of the biggest challenges in modern science. In 1982, Richard P. Feynman envisioned that the best way to emulate the behavior of many-particle quantum systems is to use another quantum system, starting the field of quantum simulation. Rather than seeking to solve the fundamental equations of quantum mechanics using conventional or classical computers, in quantum simulation one seeks to simulate a quantum system using an "analog device" mimicking its behavior, hoping to access solutions which are not easy to compute otherwise. In this talk, using the quantum annealing simulator device developed by D-Wave as a main tool, I will show that the use of tensor network methods has a key role in quantum simulation: besides benchmarking the quantum device, they can assess and help establishing its functionality beyond the classically simulatable regime [1].
Venue: via Zoom
Event Official Language: English
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Seminar
Moss sporophytes and their consumers: an overlooked interaction
May 22 (Thu) 13:00 - 14:00, 2025
Yume Imada (Assistant Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)
The evolution of plant-feeding in animals is deeply intertwined with the unintentional transport of diaspores. Zoochory (the dispersal of plant diaspores by animals) has been extensively studied in flowering plants, particularly with regard to seeds and fruits. Bryophytes, in contrast, have poorly been investigated, despite possessing traits favorable for animal-mediated dispersal: they are small, easily transported, and exhibit high totipotent capacity. It has long been believed that bryophytes are rarely consumed by animals. However, our field survey into sporophyte-feeding across diverse forest-dwelling mosses (the largest clade of bryophytes) revealed the ubiquity of spore consumption. This finding prompts a re-evaluation of the ecological function of the sporophyte in the alternation of generations in mosses. Moreover, our data suggest that this interaction may be framed within the mutualism–antagonism continuum. Finally, I aim to clarify key questions surrounding the reproduction and dispersal of spore-producing plants, particularly bryophytes.
Venue: via Zoom (Main Venue) / Seminar Room #359
Event Official Language: English
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Seminar
Universality class for driven interfaces and... integrable spin hydrodynamics?
May 19 (Mon) 15:00 - 17:00, 2025
Kazumasa A. Takeuchi (Associate Professor, Graduate School of Science, The University of Tokyo)
The Kardar-Parisi-Zhang (KPZ) universality class, originally formulated to describe driven systems such as growing interfaces, has undergone several paradigm shifts [1]. One major breakthrough was the discovery of exact solutions for one-dimensional models within the KPZ class — remarkable given their non-equilibrium and non-linear nature — enabled by underlying integrability. These exact results revealed nontrivial fluctuation properties, some closely linked to random matrix theory, which were subsequently observed in real experiments on driven interfaces. But more recently, the KPZ framework appears to be entering a new phase, extending unexpectedly to integrable spin chains at thermal equilibrium [2,3]. Although this connection was nearly dismissed when clear discrepancy in full counting statistics was reported, the speaker and collaborators numerically found that various two-point quantities agree precisely with KPZ exact solutions, so the KPZ class indeed governs integrable spin chains, yet only their two-point quantities [4]. I will also discuss a recent hydrodynamic theory aiming to bridge spin chains and KPZ, which, currently, falls short of fully explaining the numerical observations and calls for further refinement [2,3].
Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359
Event Official Language: English
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Seminar
Stable homotopy theory of invertible quantum spin systems
May 16 (Fri) 16:00 - 18:00, 2025
Yosuke Kubota (Associate Professor, Graduate School of Science, Kyoto University)
In the past decade, A. Kitaev proposed that the set of invertible gapped quantum spin systems would form an \Omega-spectrum. This conjecture is considered to have potentially significant application to the study of SPT phases. Recently, we give a mathematically rigorous realization of this proposal with the language of functional analysis and operator algebra. This gives a unified proof of a series of existing researches. The proof also suggests to understand Kitaev's proposal from the viewpoint of coarse geometry of metric spaces. This association leads us to the concept of localization flow.
Venue: Seminar Room #359 (Main Venue) / via Zoom
Event Official Language: English
1013 events