Quantum uncertainty of fields and its effect on entanglement generation in quantum particles

May 31 (Wed) at 14:00 - 15:15, 2023

Yuki Sugiyama (Ph.D. Student, Department of Physics, Graduate School of Science, Kyushu University)

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 quantum-gravity-induced-entanglement of masses (QGEM) scenario, which is expected to observe the quantum nature of non-relativistic gravity, has recently attracted great attention. In this talk, we show the effect of relativistic fields on entanglement generation based on quantum field theory. We also discuss the relationship between the entanglement generation and quantum uncertainty of the fields.

Venue: Seminar Room #359 / via Zoom

Event Official Language: English

Spectral correlations and scrambling dynamics in Sachdev-Ye-Kitaev type models

May 30 (Tue) at 13:30 - 15:00, 2023

Masaki Tezuka (Assistant Professor, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

Note: Due to unexpected trouble, we have made the decision to postpone the seminar scheduled for February 21 to May 30. Sorry for the trouble. Abstract: The Sachdev-Ye-Kitaev (SYK) model, proposed in 2015, is a quantum mechanical model of N Majorana or complex fermions with all-to-all random four-body interactions. The model has attracted significant attention over the years due to its features such as the existence of the large-N solution with maximally chaotic behavior at low temperatures and holographic correspondence to low-dimensional gravity. The sparse version of the SYK model reproduces essential features of the original model for reduced numbers of disorder parameters. We recently proposed [1] a further simplification, where we set the nonzero couplings to be +1 or -1 rather than sampling from a continuous distribution such as Gaussian. This binary-coupling model exhibits strong correlations in the spectrum, as observed in the spectral form factor, more efficiently in terms of the number of nonzero terms than in the Gaussian distribution case. We also discuss the scrambling dynamics with the binary-coupling sparse SYK model, comparing the model with the original model as well as the SYK model with random two-body terms [2], where the localization of the many-body eigenstates in the Fock space has been quantitatively studied [3,4].

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Molecular and evolutionary bases of Pieris butterflies for overcoming diverse chemical defenses in their host plants

May 25 (Thu) at 16:00 - 17:00, 2023

Yu Okamura (JSPS Research Fellow PD, Department of Biological Sciences, Graduate School of Science, The University of Tokyo)

In terrestrial ecosystems, plants and herbivorous insects account for more than half of the described species and play quite important ecological roles. Plants and herbivorous insects have strong chemical interaction as plants defend themselves with various defense compounds such as secondary metabolites and herbivores adapt to it by evolving detoxification mechanisms. Larvae of Pieris butterflies feed on Brassicaceae plants as the main host. Brassicaceae plants contain diverse glucosinolates (GLS) as a main chemical defense, which can be rapidly hydrolyzed into toxic isothiocyanates by a plant enzyme called myrosinase upon tissue damage. Larvae of Pieris butterflies are known to express nitrile-specifier protein in their gut and this can redirect toxic breakdown products of GLSs to less toxic metabolites. Although NSP is considered an evolutionary key innovation for Pieridae that enabled these butterflies to colonize GLS-containing plants, it has been largely unclear whether NSP is enough for Pieris butterfly larvae to overcome the diverse types of GLS they encounter in their host plants. In this seminar, I would like to introduce our recent findings showing that Pieris butterfly larvae not only use NSP but also use its ortholog major allergen (MA) to overcome the diverse types of GLS in their Brassicaceae host plants. We found that Pieris larvae show fine-tuned regulation of those two adaptive genes depending on the chemical profiles of their host plants. Furthermore, those two adaptive genes have different evolutionary trajectories in macro- and micro-evolutionary scales among Pieris species or populations associated with their pattern of host plant usage. Moreover, with an approach using CRISPR/Cas9 genome editing, we showed that both NSP and MA have different but complementary roles in disarming GLS-based defenses in their host plants and that both genes are crucial for Pieris in overcoming their host plant’s major chemical defense. Those highlight that having both NSP and MA is a key for Pieris butterflies to overcome the diverse types and GLS and, consequently, adapt to a wider range of Brassicaceae hosts. Our results illuminate that gene duplication, functional differentiation, and the evolution of gene regulation mechanisms are all crucial for herbivorous insects to overcome co-evolving chemical defenses in their host plants.

Venue: via Zoom

Event Official Language: English

Hydrodynamic limit and the fluctuating hydrodynamics for large-scale interacting systems

May 24 (Wed) at 14:00 - 16:30, 2023

Kohei Hayashi (Visiting Researcher, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

In these decades, a great deal of works has been devoted to understand macroscopic phenomena, such as diffusion, aggregation or pattern formation, from the viewpoint of microscopic systems. Hydrodynamic limit, or fluctuating hydrodynamics, is a fundamental framework to explain the macroscopic behavior of physical quantities in mathematically rigorous ways from a system of the vast numbers of microscopic agents under random interactions, which system is called the large-scale interacting system. In this framework, our central aim is to derive partial differential equations (PDEs) which describe time evolution of some macroscopic quantities, starting from the large-scale interacting systems; hydrodynamic limit is a procedure to derive deterministic PDEs with help of the law of large numbers, whereas stochastic PDEs are derived under the scale of the central limit theorem by fluctuating hydrodynamics. In this talk, I would like to explain basic concepts of hydrodynamic limit and fluctuating hydrodynamics, through some simple models. In the first part, I will give a concise exposition on Markov processes as preliminaries and then state some results on scaling limits of simple exclusion processes as a pedagogical example. In the second part, I will talk about recent progress on universality which appears in fluctuating hydrodynamics. Especially, I would like to talk about the universality of the Kardar-Parisi-Zhang equation, and its mathematical background.

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

Event Official Language: English

Statistical methods to probe binary stellar evolution with ZTF and LISA data

May 23 (Tue) at 13:30 - 15:00, 2023

Lucy McNeill (JSPS Fellow, Department of Physics, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

The Laser-Interferometer-Space-Antenna (LISA) will be capable of detecting all galactic double neutron star binaries (DNSBs) with orbital periods < 20 minutes, as well as 10-100’s of thousands of double white dwarf binaries. I will present our method to use LISA detections to constrain the formation frequencies of galactic DNSBs, which are determined by supernova physics and various mass exchange processes. Next, I summarise the key differences in DNSBs and white dwarf binaries (WDBs) in the context of future LISA observations, as well as the current Zwicky Transient Facility (ZTF) for the latter. Then we will examine the current catalogue of short period white dwarf binaries (orbital periods < 1 hour) detected by ZTF so far, including the first ever measurement (Burdge et al. 2023) of the temperature of a mass transferring white dwarf in a binary. Here I will make the case that taken together, these observations are in conflict with the theoretical picture commonly used in Galactic modelling- specifically related to cooling and mass transfer leading to WDB mergers. However, heating from tidal interactions may explain and mediate this inconsistency. Finally I will put these results into context regarding preparing for the unprecedented data set of galactic white dwarf binaries from LISA in the 2030s.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

X-ray study on the synchrotron emission in Kepler's SNR

May 19 (Fri) at 14:00 - 15:15, 2023

Vincenzo Sapienza (Ph.D. Student, Department of Physics, Graduate School of Science, The University of Tokyo)

Synchrotron X-ray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high energy electrons accelerated at the shock front. We performed a spatially resolved spectral analysis of the young Kepler's SNR, where we identify two different regimes of particle acceleration. In the north, where the shock interacts with a dense circumstellar medium (CSM), we 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. We 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, we found some regions where we 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 If I will have time during the seminar it will be nice to present also some preliminary results I will have in the SN 1987A project.

Venue: Seminar Room #359 / via Zoom

Event Official Language: English

Excursion Theory, Galton Watson Trees and their Scaling Limits

May 18 (Thu) at 16:00 - 17:00, 2023

Christy Koji Kelly (Special Postdoctoral Researcher, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

In this talk we aim to introduce a recent perspective in probability theory that views random trees as random excursions with additional data. This perspective is particular suited to the study of the scaling limit of tree-valued random processes. Excursion theory is a useful and relatively elementary tool allowing one to derive rather explicit information about the local and global geometry of the resultant continuum trees which in turn can be used to derive information about large random trees. We illustrate these ideas in the context of the Brownian continuum random tree, the scaling limit of critical Galton-Watson trees and a structure that arises naturally in various contexts in physics; in particular the Brownian continuum random tree is a pathological model of quantum spacetime. Despite the fundamentally mathematical nature of the talk, the aim is to keep the presentation essentially heuristic emphasising key intuitions over rigorous proof. The content itself should be relevant to biologists interested in the theory of branching processes or coalescent theory.

Venue: Seminar Room #359 / via Zoom

Event Official Language: English

Exploring GPT’s Influence on Natural Science and Mathematics

May 17 (Wed) at 10:00 - 15:00, 2023

We are organizing a workshop to explore the application of ChatGPT in natural sciences, with a focus on theoretical physics and mathematics. Advances in GPT-4 and plugin technology are expected to bring about transformative changes in the way research is conducted. We will investigate the potential for another shift in research methodology following the advent of computers. Expert-led lectures on large language models (LLMs/ChatGPT) will also be conducted. We aim to deepen the discussion on the effective utilization of LLMs as tools to support the research of physicists and mathematicians. This workshop will be held in a hybrid format, combining online streaming with in-person presentations, to accommodate a larger number of participants. In addition to the lectures, short talks and discussions will be held entirely offline. The target audience is mainly students and researchers in the natural sciences, but please note that there will be a limit to the number of in-person attendees. The aim of this event is to provide a forum for researchers to engage in earnest discussions. Those who do not align with the objectives of this workshop are kindly asked to refrain from participating. We look forward to this opportunity to consider, together with all of you, new research methods and perspectives in the fields of theoretical physics and mathematics in the natural sciences, utilizing ChatGPT. (The above text was created by modifying the text generated by Chat-GPT and GPT-4.) All talks will be delivered in Japanese.

Venue: #435-437, 4F, Main Research Building (Main Venue) / via Zoom

Event Official Language: Japanese

Ground-state phases of the one-dimensional SU(N)-symmetric Kondo lattice model

May 11 (Thu) at 17:00 - 18:15, 2023

Keisuke Totsuka (Associate Professor, Yukawa Institute for Theoretical Physics, Kyoto University)

The Kondo-lattice model and its variants (e.g., the Kondo-Heisenberg model), in which itinerant fermions interact with immobile magnetic moments via spin-exchange coupling (Kondo coupling), have been playing an important role in understanding the physics of heavy-fermion systems. In this talk, I begin by quickly explaining how the SU(N) Kondo-lattice model, in which the spin SU(2) symmetry is generalized to SU(N), is realized in actual physical systems (e.g., cold fermions and twisted bilayer graphene), and then I focus on the ground-state properties of its one-dimensional version. Specifically, when the Kondo coupling is sufficiently large, we find ferromagnetic metallic phases that can be established rigorously as well as several insulating ones. I also show that the SU(N) Kondo-lattice model provides a natural condensed-matter realization of supersymmetric [i.e., SU(N|1)] models. Various (insulating) phases at small Kondo coupling are then explored using the machinery of bosonization and various conformal field theory (CFT) techniques, and the results are compared with the predictions of the Lieb-Schultz-Mattis-type (or anomaly-matching) argument. Field: condensed matter physics Keywords: Kondo lattice model, SU(N) symmetry, supersymmetry, heavy-fermion systems, bosonization, conformal field theory

Venue: via Webex

Event Official Language: English

Conditions for maintaining pseudo-overdominance

May 11 (Thu) at 16:00 - 17:00, 2023

Diala Abu Awad (Associate Professor, Génétique Quantitative et Évolution - Le Moulon, Université Paris-Saclay, France)

Deleterious recessive mutations should purge or fix within inbred populations, yet inbred populations often retain moderate to high segregating load. However, arrays of deleterious recessives linked in repulsion could generate appreciable pseudo-overdominance, mimicking overdominant selection that would sustain segregating load. We use analytical approches and simulations to explore whether and for how long pseudo-overdominant (POD) zones can persist once created (e.g., by hybridization between populations fixed for alternative mildly deleterious mutations). Balanced haplotype loads, tight linkage, and moderate to strong cumulative selective effects all serve to maintain POD zones. Tight linkage is key, suggesting that such regions are most likely to arise and persist in low recombination regions (like inversions). Selection and drift unbalance the load, eventually eliminating POD zones, but this process is quite slow, and could influence short term evolution of populations.

Venue: via Zoom

Event Official Language: English

Quantum transport with cold atoms

May 10 (Wed) at 13:30 - 15:00, 2023

Shun Uchino (Researcher, Advanced Science Research Center, Japan Atomic Energy Agency (JAEA))

Quantum transport occurring through a mesoscopic conduction region allows us to extract interesting quantum many-body phenomena. For decades, solid-state systems have been the playground of such transport and revealed nontrivial outcomes such as the conductance quantization in a quantum point contact system and the fractional charge measurement in a fractional quantum Hall system. More recently, cold atoms trapped in the vacuum have served as the complementary system to study the quantum transport phenomena. In this seminar, I wish to discuss the recent progresses of quantum transport with cold atoms. The great advantages of those systems are that one can control quantum statistics, inter-particle interactions, dissipation, and dimensions. I try to show that such controllability enables to explore a regime of quantum transport that has yet to be reached with solid-state materials, including transport of bosons, dissipation effect in transport, and transport with synthetic dimensions.

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

Event Official Language: English

Generalized AKS scheme of integrability via vertex algebra

May 9 (Tue) at 16:15 - 17:15, 2023

Wenda Fang (Ph.D. Student, Research Institute for Mathematical Sciences (RIMS), Kyoto University)

In this talk, we define and study the classical R-matrix for vertex Lie algebra, based on which we propose to construct a new vertex Lie algebra. As an application, using the classical R-matrix we defined, we give a new scheme to construct infinite-dimensional (Liouville) integrable systems via the Feigin-Frenkel center. This seminar is on-site only.

Venue: Seminar Room #359

Event Official Language: English

On the Beem-Nair conjecture

May 9 (Tue) at 15:00 - 16:00, 2023

Syun Furihata (Ph.D. Student, Research Institute for Mathematical Sciences (RIMS), Kyoto University)

Given a simple Lie group G, we have an open immersion (constructed by Beem and Nair) from the Kostant-Toda lattice associated to G into the universal centralizer of G. They expected that a free field realization of the chiral universal centralizer of G at the critical level will be obtained by the chiralization of this immersion. In this talk, we will verify this conjecture is true by constructing an embedding from the chiral universal centralizer into an appropriate vertex operator algebra at any level. This seminar is on-site only.

Venue: Seminar Room #359

Event Official Language: English

The 22nd MACS Colloquium

April 28 (Fri) at 15:00 - 18:30, 2023

Masaaki Imaizumi (Associate Professor, Graduate School of Arts and Sciences, The University of Tokyo)

15:00-16:00 Talk by Dr. Masaaki Imaizumi (Graduate School of Arts and Science, The University of Tokyo) "Theory of Deep Learning and Overparameterization" 16:15-17:20 2023 Study Group introduction session 17:30-18:00 Discussion

Venue: Maskawa Hall, 1F, Maskawa Building for Education and Research

Event Official Language: Japanese

Introduction to Genomics

April 27 (Thu) at 16:00 - 17:00, 2023

Jeffrey Fawcett (Senior Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

A 'genome' is a single set of genetic information of a given individual, which is encoded by the nucleotide sequence of the DNA. For instance, the human genome consists of around 3 billion nucleotide base pairs, although the size and content of the genome differs greatly across species and individuals. Some species such as the budding yeast has a genome as small as 12 million base pairs, whereas other species such as Paris japonica, a flowering plant native to the sub-alpine regions of Japan, is said to have a genome as large as 150 billion base pairs. In this talk, I will give a introduction of what kind of information is contained within a genome, and how that differs across species and individuals. This talk will be introductory and aimed at non-experts including non-biologists.

Venue: via Zoom

Event Official Language: English

Spring Workshop on Quantum Gravity

April 26 (Wed) - 28 (Fri), 2023

This is co-hosted by iTHEMS and NCTS, and is also the first of Quantum Gravity Gatherings. What is space-time? How did the universe begin? Various approaches exist toward theories of quantum gravity that can answer such fundamental questions. Each approach has its own strengths and weaknesses and should capture, at least partially, some essential aspect of quantum gravity. Then, what are the general properties (if any) of the quantum nature of gravity independent of the details of such approaches? As the main speaker, we have asked Hikaru Kawai to give an intensive talk approaching this question from both general and specific arguments in a style consistent with the concept of Quantum Gravity Gatherings. We hope that the younger generation will experience his powerful arguments based on his experience and deep insights. This workshop is intended to be a lively and participatory event, not just a listening experience. For this reason, the number of participants will be limited to about 30 with priority given to graduate students and young post-docs; the intensive talk will be given in a face-to-face blackboard style (in English, no online streaming) to allow for informal and lively Q&A discussions. In addition, there will be sessions where any participant can give a short talk on any topic of his/her choice. Through these, all the participants will discuss the above question from various angles, and the young generations in Japan and Taiwan will stimulate each other and start new exchanges.

Venue: #435-437, 4F, Main Research Building

Event Official Language: English

Search for TeV-scale WIMP Dark Matter by observing Gamma rays around the Galactic Centre with the MAGIC telescopes and future prospects.

April 25 (Tue) at 11:00 - 12:00, 2023

Tomohiro Inada (Shuimu Tsinghua Fellow, Department of Physics, National Tsinghua University, Beijin, China)

Line-like features in TeV γ rays constitute a “smoking gun” for TeV-scale particle dark matter and new physics. Probing the Galactic Centre region with ground-based Cherenkov telescopes enables the search for TeV spectral features in immediate association with a dense dark matter reservoir at a sensitivity out of reach for satellite γ-ray detectors, and direct detection and collider experiments. I will report on about seven years of observations of the Galactic Centre region with the MAGIC stereoscopic telescope system reaching γ-ray energies up to 100 TeV. We constrain the cross-section for dark matter annihilation into two photons, achieving the best limits to date for a dark matter mass above 20 TeV and a cuspy dark matter profile at the Galactic Centre. I would like to discuss how to constrain supersymmetric wino models, which are one of the most popular dark matter candidates in the context of the Lightest Supersymmetric Particles (LSPs).

Venue: via Zoom

Event Official Language: English

iTHEMS x academist Online Event "World of Mathematical Sciences 2023"

April 22 (Sat) at 10:00 - 16:30, 2023

Takumi Doi (Senior Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))
Ryo Namba (Senior Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))
Yuto Moriwaki (Special Postdoctoral Researcher, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))
Kyosuke Adachi (Special Postdoctoral Researcher, Nonequilibrium Physics of Living Matter RIKEN Hakubi Research Team, RIKEN Center for Biosystems Dynamics Research (BDR))
Natsuki Tomida (Specially Appointed Assistant Professor, Center for Science Adventure and Collaborative Research Advancement (SACRA), Graduate School of Science, Kyoto University)

Venue: via Zoom

Event Official Language: Japanese

Machine learning predicts biological system evolution by gene gains and losses

April 20 (Thu) at 16:00 - 17:00, 2023

Naoki Konno (Ph.D. Student, Department of Biological Sciences, Graduate School of Science, The University of Tokyo)

Prediction of evolution is a fundamental goal of biology with a potential impact on strategic pathogen control and genome engineering. While predictability of short-term and sequence-level evolution has been investigated, that of long-term and system-level evolution has not been systematically examined. Here, we show that evolution of metabolic systems by gene gains and losses is generally predictable by applying ancestral gene content reconstruction and machine learning techniques to ~3000 bacterial genomes. Our framework, Evodictor, successfully predicted gene gain and loss events at the branches of the reference phylogenetic tree, suggesting universally shared evolutionary pressures and constraints on metabolic systems. I herein present the mathematical model of Evodictor and our findings on evolutionary rules from physiological and ecological aspects. I will further discuss potential versatility of Evodictor approach to analyze various diversification processes along branching lineage trees, not only evolution, but also developmental processes.

Venue: via Zoom

Event Official Language: English

Towards EeV Neutrino Astronomy with GRAND

April 18 (Tue) at 14:00 - 15:15, 2023

Kumiko Kotera (Director of Research, Institute of Astrophysics, France)

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 multi-messenger picture resides in the highest energies, as no ultra-high 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 ultra-high energy particles, with a colossal array of 200'000 antennas over 200'000 km2, split into ~20 sub-arrays of ~10'000 km2 deployed worldwide. In this talk, we will present 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.

Venue: Common Room #246-248 / via Zoom

Event Official Language: English