セミナー
1000 イベント
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セミナー
Quantum uncertainty of fields and its effect on entanglement generation in quantum particles
2023年5月31日(水) 14:00 - 15:15
杉山 祐紀 (九州大学 大学院理学府 物理学専攻 博士課程)
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.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
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セミナー
Spectral correlations and scrambling dynamics in Sachdev-Ye-Kitaev type models
2023年5月30日(火) 13:30 - 15:00
手塚 真樹 (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 助教)
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].
会場: 研究本館 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
Molecular and evolutionary bases of Pieris butterflies for overcoming diverse chemical defenses in their host plants
2023年5月25日(木) 16:00 - 17:00
岡村 悠 (東京大学 大学院理学系研究科 生物科学専攻 日本学術振興会 特別研究員 PD)
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.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Hydrodynamic limit and the fluctuating hydrodynamics for large-scale interacting systems
2023年5月24日(水) 14:00 - 16:30
林 晃平 (理化学研究所 数理創造プログラム (iTHEMS) 訪問研究員)
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.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Statistical methods to probe binary stellar evolution with ZTF and LISA data
2023年5月23日(火) 13:30 - 15:00
ルーシー・マクニール (京都大学 大学院理学研究科 物理学・宇宙物理学専攻 特別研究員)
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.
会場: 研究本館 3階 359号室とZoomのハイブリッド開催
イベント公式言語: 英語
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セミナー
X-ray study on the synchrotron emission in Kepler's SNR
2023年5月19日(金) 14:00 - 15:15
Vincenzo Sapienza (東京大学 大学院理学系研究科 物理学専攻 博士課程)
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.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
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セミナー
Excursion Theory, Galton Watson Trees and their Scaling Limits
2023年5月18日(木) 16:00 - 17:00
クリスティ・コウジ・ケリー (理化学研究所 数理創造プログラム (iTHEMS) 基礎科学特別研究員)
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.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
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セミナー
Ground-state phases of the one-dimensional SU(N)-symmetric Kondo lattice model
2023年5月11日(木) 17:00 - 18:15
戸塚 圭介 (京都大学 基礎物理学研究所 准教授)
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
会場: via Webex
イベント公式言語: 英語
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セミナー
Conditions for maintaining pseudo-overdominance
2023年5月11日(木) 16:00 - 17:00
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.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Quantum transport with cold atoms
2023年5月10日(水) 13:30 - 15:00
内野 瞬 (日本原子力研究開発機構 先端基礎科学センター 研究員)
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.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Generalized AKS scheme of integrability via vertex algebra
2023年5月9日(火) 16:15 - 17:15
Wenda Fang (京都大学 数理解析研究所 (RIMS) 博士課程)
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.
会場: セミナー室 (359号室)
イベント公式言語: 英語
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セミナー
On the Beem-Nair conjecture
2023年5月9日(火) 15:00 - 16:00
降旗 駿 (京都大学 数理解析研究所 (RIMS) 博士課程)
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.
会場: セミナー室 (359号室)
イベント公式言語: 英語
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セミナー
Introduction to Genomics
2023年4月27日(木) 16:00 - 17:00
ジェフリ・フォーセット (理化学研究所 数理創造プログラム (iTHEMS) 上級研究員)
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.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Search for TeV-scale WIMP Dark Matter by observing Gamma rays around the Galactic Centre with the MAGIC telescopes and future prospects.
2023年4月25日(火) 11:00 - 12:00
稲田 知大 (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).
会場: via Zoom
イベント公式言語: 英語
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セミナー
Machine learning predicts biological system evolution by gene gains and losses
2023年4月20日(木) 16:00 - 17:00
今野 直輝 (東京大学 大学院理学系研究科 生物科学専攻 博士課程)
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.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Towards EeV Neutrino Astronomy with GRAND
2023年4月18日(火) 14:00 - 15:15
クミコ・コテラ (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.
会場: コモンルーム (246-248号室) / via Zoom
イベント公式言語: 英語
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セミナー
Why are cell populations maintained via multiple compartments?
2023年4月13日(木) 10:00 - 11:00
カルメン・モリナ パリス (Researcher, Theoretical Biology and Biophysics, Los Alamos National Laboratory, USA)
We consider the maintenance of “product” cell populations from “progenitor” cells via a sequence of one or more cell types, or compartments, where each cell’s fate is chosen stochastically. If there is only one compartment then large amplification, that is, a large ratio of product cells to progenitors comes with disadvantages. The product cell population is dominated by large families (cells descended from the same progenitor) and many generations separate, on average, product cells from progenitors. These disadvantages are avoided using suitably-constructed sequences of compartments: the amplification factor of a sequence is the product of the amplification factors of each compartment, while the average number of generations is a sum over contributions from each compartment. Passing through multiple compartments is, in fact, an efficient way to maintain a product cell population from a small flux of progenitors, avoiding excessive clonality and minimising the number of rounds of division en route. We analyse the possible descendants of one progenitor cell, families of cells that journey through the sequence of compartments. We find that the ability of product cells to perform their function may be negatively affected by the number of rounds of cell division that separates them from their progenitor, because every round of division brings with it a risk of mutation.
会場: via Zoom
イベント公式言語: 英語
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セミナー
An overview on the nuclear equation of state studied from ground and collective excited state properties of nuclei
2023年4月12日(水) 13:30 - 15:00
Xavier Roca-Maza (Associate Professor, Department of Physics, University of Milan, Italy)
This contribution reviews a selection of available constraints to the nuclear equation of state (EoS) around saturation density from nuclear structure calculations on ground and collective excited state properties of atomic nuclei [1]. It concentrates on predictions based on self-consistent mean-field calculations, which can be considered as an approximate realization of an exact energy density functional (EDF). Mostly, EDFs are currently derived from effective interactions commonly fitted to nuclear masses, charge radii and, in many cases, also to pseudo-data such as nuclear matter properties. Although in a model dependent way, EDFs constitute nowadays a unique tool to reliablyand consistently access bulk ground state and collective excited state properties of atomic nuclei along the nuclear chart as well as the EoS. The impact on the EoS of the new CREx [2] and PREx [3] measurments of the parity violating asymmetry (ground state observable) in 48Ca and 208Pb, respectively, will be also discussed [4,5] and compared to previously presented results on collective excitations. As the main conclusion, the isospin dependence of the nuclear EoS around saturation density and, to a lesser extent, the nuclear matter incompressibility remain to be accurately determined. Experimental and theoretical efforts in finding and measuring observables specially sensitive to the EoS properties are of paramount importance, not only for low-energy nuclear physics but also for nuclear astrophysics applications.
会場: 理化学研究所 和光キャンパス RIBF棟 2階 大会議室 (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Quantum modularity of quantum invariants and related techniques
2023年4月11日(火) 13:00 - 15:30
村上 友哉 (九州大学 数理学研究院 日本学術振興会 特別研究員 PD)
In this talk, I will present my recent work[1] and related research. In the first half of the talk, I will provide an overview of the concept of quantum modularity of quantum invariants, and briefly discuss my main result. In the second half, I will provide a more detailed explanation of my main result and the proof.
会場: セミナー室 (359号室) (メイン会場) / via Zoom
イベント公式言語: 英語
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セミナー
Frobenius algebras associated with the α-induction for equivariantly braided tensor categories
2023年4月10日(月) 14:00 - 16:30
及川 瑞稀 (東京大学 大学院数理科学研究科 博士課程／日本学術振興会 特別研究員 DC)
In this talk, I would like to introduce my work https://arxiv.org/abs/2303.11845. In the first half of the talk, I will give an introduction of tensor categories. In the latter half, I will explain about my construction of some tensor categories and Frobenius algebras.
会場: セミナー室 (359号室) / via Zoom
イベント公式言語: 英語
1000 イベント