セミナー
764 イベント
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セミナー
Renormalization Group Approach for Machine Learning Hamiltonian
2024年9月10日(火) 15:00 - 17:00
尾澤 岬 (CNRS Researcher, Laboratory for Interdisciplinary Physics (LIPhy), Université Grenoble Alpes, France)
We develop a multiscale approach to estimate high-dimensional probability distributions. Our approach applies to cases in which the energy function (or Hamiltonian) is not known from the start. Using data acquired from experiments or simulations we can estimate the underlying probability distribution and the associated energy function. Our method—the wavelet-conditional renormalization group (WCRG)—proceeds scale by scale, estimating models for the conditional probabilities of “fast degrees of freedom” conditioned by coarse-grained fields, which allows for fast sampling of many-body systems in various domains, from statistical physics to cosmology. Our method completely avoids the “critical slowing-down” of direct estimation and sampling algorithms. This is explained theoretically by combining results from RG and wavelet theories, and verified numerically for the Gaussian and φ4-field theories, as well as weak-gravitational-lensing fields in cosmology. Misaki Ozawa obtained his Ph.D. in 2015 from the University of Tsukuba. He did his first postdoc at the University of Montpellier in France. He then moved to Ecole Normale Supérieure (ENS) Paris as the second postdoc. Currently, he is a CNRS permanent researcher at Grenoble Alpes Univeristy in France. His background is in the physics of disordered systems such as glasses and spin glasses. He is also working on interdisciplinary studies between statistical physics and machine learning.
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
A model to unify the theory of speciation
2024年9月5日(木) 16:00 - 17:00
ホセ サイード・グティエレス オルテガ (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)
Speciation, the process by which new species originate, occurs due to geographic (physical distance), ecological (different background environments), and historical (divergence time) factors that promote reproductive isolation among lineages. However, we don’t know how these factors interplay; therefore, our empirical and theoretical knowledge about speciation is limited, fragmented, and lacks unification. To fill this knowledge gap, I propose a model and an experiment that treats speciation as a continuum of the interplay between geographic and ecological factors. Empirical evidence has shown that the extremes of this continuum produce high evolutionary rate (faster speciation), while I expect that intermediate values in the interplay continuum would produce reduced evolutionary rates. I expect this seminar can open opportunities for collaboration.
会場: via Zoom / 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
Chromatophore patterns, packing, and scaling on a growing squid
2024年8月20日(火) 16:00 - 17:00
ロバート・ロス (沖縄科学技術大学院大学 (OIST) 生物複雑性ユニット / 計算行動神経科学ユニット 学際研究員)
Many biological patterns are formed during growth, and various modeling approaches have repeatedly shown that growth can substantially impact pattern formation. However, experimental testing of these ideas has been limited, largely due to the difficulty in precisely measuring organism growth while simultaneously tracking the dynamics of pattern formation. To address this, we turned to the skin of the oval squid. The oval squid grows rapidly, hatching with a length of approximately 16mm and reaching 90mm within 3 months. Throughout development, its skin is populated by pigment-filled cells called chromatophores. Following insertion into the skin, chromatophores do not move. This means that squid chromatophores, besides being the constitutive elements of a point pattern, can also function as reference points to precisely determine skin growth. For the more biologically-minded, I will explain how the chromatophore pattern emerges through the interplay of growth and decreasing chromatophore growth rates. For those who lean physics, I will talk about how due to the combination of volume exclusion and growth, chromatophores exhibit a scaling in which relative density fluctuations grow with spatial scale, akin to a critical system.
会場: セミナー室 (359号室) 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
Social behavior and social engineering in bacteria
2024年8月1日(木) 16:00 - 17:00
Ashleigh Griffin (Professor, Department of Biology, University of Oxford, UK)
This year is the 60th anniversary of WD Hamilton’s seminal paper in which he outlined his theory of inclusive fitness and showed how it could be used to understand altruism in the social insects. In this talk, I will describe efforts made to use his theory to understand social behavior in bacteria. And I’ll go on to explore the potential of using these insights to tackle problems of antibiotic resistance in infections.
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
Algebraic curves and parametric resurgence
2024年7月29日(月) 16:30 - 17:45
Samuel Crew (Postdoctoral Fellow, Imperial College London, UK)
In this talk I will discuss recent work together with Ines Aniceto (Southampton) on algebraic examples of parametric resurgence. We discuss a simple example to elucidate the so-called higher order Stokes phenomena and discuss how a Borel inner-outer matching procedure allows us to view parametric resurgence as a series of non-parametric resurgence problems.
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
Lectures on Black Holes, Holography and Quantum Gravity
2024年7月29日(月) - 8月1日(木)
野村 泰紀 (Director, Berkeley Center for Theoretical Physics, University of California, Berkeley, USA)
The information problem of black holes has evolved modern physics and led to the holographic principle, considered the fundamental principle of quantum gravity. Through a series of four lectures (blackboard style), including naive questions from the audience and lively discussions, I will introduce these fundamental ideas as well as the current state of the art and problems in cutting-edge research. Lecture 1: July 29 (Mon) 13:30~15:00 (Lecture 2: July 30 (Tue) 13:30~15:00 was canceled) Lecture 3: July 31 (Wed) 13:30~15:00 Lecture 4: Aug 1 (Thu) 13:30~15:00 (+ A possible lecture )
会場: セミナー室 (359号室) 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
Stringy Nonlocality: Operator Formalism and Implications
2024年7月26日(金) 14:00 - 15:30
ウェイシャン・シャオ (Ph.D. Student, Department of Physics, National Taiwan University, Taiwan)
Nonlocality is a fundamental property of string theory, where point-like particles are replaced by extended strings. This feature is especially evident in string field theories, where field components interact through form factors containing spacetime derivatives of infinite order. The usual approach to canonical quantization is no longer applicable, and thus a non-perturbative treatment of nonlocal effects at the quantum level remains unclear. In this seminar, I will discuss a recent attempt to construct an operator formalism for stringy nonlocal field theories, and explore the potential implications for black hole radiation and primordial fluctuations in the early universe.
会場: セミナー室 (359号室) 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
Multi-Agent Reinforcement Learning for Exploring Collective Behavior
2024年7月25日(木) 16:00 - 17:00
筒井 和詩 (東京大学 大学院総合文化研究科 助教)
Humans and other organisms develop collective behaviors through interactions with diverse environments and various species. These behaviors are significant topics across multiple research fields, including evolutionary biology, behavioral ecology, and animal sociology. Unraveling the decision-making mechanisms of individuals in groups within cooperative and competitive contexts has captured the attention of many researchers but remains a complex challenge. This seminar will present research cases that employ multi-agent reinforcement learning, a machine learning technique, to investigate the decision-making processes underlying collective behavior. Through this approach, we aim to provide deeper insights into the dynamics and mechanisms that drive group behaviors in various biological systems.
会場: セミナー室 (359号室) 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
Symmetries and Generalization for Machine Learning on a Lattice
2024年7月23日(火) 15:00 - 16:30
Andreas Ipp (Senior Scientist, Institute for Theoretical Physics, TU Wien, Austria)
Symmetries such as translations and rotations are crucial in physics and machine learning. The global symmetry of translations leads to convolutional neural networks (CNNs), while the much larger space of local gauge symmetry has driven us to develop lattice gauge equivariant convolutional neural networks (L-CNNs). This talk will discuss how the challenges of simulating the earliest stage of heavy ion collisions led us to use machine learning and how these innovations could improve lattice simulations in the future. Andreas Ipp is a Senior Scientist at the Institute for Theoretical Physics at TU Wien. He received his PhD in 2003 and held postdoctoral positions at ECT* in Trento and the Max-Planck-Institute in Heidelberg before returning to TU Wien in 2009. He completed his habilitation on "Yoctosecond dynamics of the quark-gluon plasma" in 2014. His current research focuses on symmetries in machine learning for applications in lattice gauge theory and heavy ion collisions.
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
Probing Majorana excitations in the Kitaev magnet α-RuCl3 through bulk heat capacity measurements
2024年7月22日(月) 10:30 - 11:45
今村 薫平 (東京大学 大学院工学系研究科 物理工学専攻 博士課程／日本学術振興会 特別研究員 DC)
Recently, the layered honeycomb material α-RuCl3 exhibits several anomalous features that are consistent with expectations of the Kitaev quantum spin liquid (KQSL) under in-plane magnetic field. Most remarkably, finite planar thermal Hall conductivity has been observed, whose magnitude is close to the half-integer quantization value expected for the chiral edge currents of Majorana fermions[1]. However, it has been reported that the thermal Hall conductivity shows strong sample dependence. Also, there are attempts to offer a different explanation by the bosonic edge excitations due to topological magnons or phonon. A key to distinguishing between fermionic and bosonic origins of unusual features in the high-field state of α-RuCl3 is the difference in the field angle dependence of the excitation gap. Therefore, we distinguish these origins from combined low-temperature measurements of high-resolution specific heat and thermal Hall conductivity with rotating magnetic fields within the honeycomb plane. A distinct closure of the low-energy bulk gap is observed for the fields in the Ru-Ru bond direction, and the gap opens rapidly when the field is tilted. Notably, this change occurs concomitantly with the sign reversal of the Hall effect. General discussions of topological bands show that this is the hallmark of an angle rotation–induced topological transition of fermions, providing conclusive evidence for the Majorana-fermion origin of the thermal Hall effect in α-RuCl3[2]. Furthermore, to understand the nature of the high-field state, it is crucial to elucidate the effects of disorder, which inevitably exists in real materials. We artificially introduce point defects by electron irradiation and compare the low-energy excitations in the pristine and irradiated sample by high-resolution specific heat measurements. We observed an additional in-gap T-linear term in C/T, whose coefficient shows distinct field-sensitive behaviors suggestive of Majorana physics in the KSL. This can be interpreted by the weak localization of Majorana fermions, which is induced by the disorder[3]. Moreover, recently, we succeed in synthesizing very high-quality crystals of α-RuCl3[4].
会場: via Zoom / セミナー室 (359号室) 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
Optimal control of stochastic reaction networks
2024年7月18日(木) 16:00 - 17:00
堀口 修平 (金沢大学 ナノ生命科学研究所 特任研究員)
Optimal control problems for the population of interacting particles arise in various fields, including pandemic management, species conservation, cancer therapy, and chemical engineering. When the population size is small, the time evolution of the particle numbers is inherently noisy and modeled by stochastic reaction networks, a class of jump processes on the space of particle number distributions. However, compared to deterministic and other stochastic models, optimal control problems for stochastic reaction networks have not been extensively studied. In this talk, I will review a formulation of stochastic reaction networks and present a new class of optimal control problems that are efficiently solvable and widely applicable. The optimal solution can be efficiently obtained using the Kullback–Leibler divergence as a control cost. We apply this framework to the control of interacting random walkers, birth-death processes, and stochastic SIR models. Both numerical and analytical solutions will be presented, highlighting the practical applications and theoretical significance of this approach.
会場: via Zoom
イベント公式言語: 英語
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セミナー
Thermal radiation exchange in primordial gravitational waves
2024年7月18日(木) 13:30 - 15:00
太田 敦久 (Postdoctoral Fellow, Institute for Advanced Study, Hong Kong University of Science and Technology, China)
The radiation-dominated universe is a key component of standard Big Bang cosmology. Radiation comprises numerous quantum elementary particles, and its macroscopic behavior is described by taking the quantum thermal average of its constituents. The dynamics of gravitational waves are considered in this smooth fluid. While interactions between individual particles and gravitational waves are often neglected in this context, it raises the question of whether such a hydrodynamical approximation is reasonable. To address this question, we explored the quantum mechanical aspects of gravitational waves in a universe dominated by a massless scalar field, whose averaged energy-momentum tensor serves as background radiation. We computed thermal loop corrections for the gravitational wave power spectrum using the Schwinger-Keldysh formalism. Interestingly, we found that the loop effect enhances the super-horizon primordial gravitational wave spectrum, indicating that the inflationary spectrum is not conserved, contrary to conventional wisdom. These findings have significant implications for our understanding of the early universe. In this talk, I will begin with the basics of cosmology and explain the significance of these results and their relevant observational consequences.
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
Quantum Simulation in High Energy Nuclear Physics
2024年7月18日(木) 10:00 - 11:30
郭 星雨 (Lecturer, Institute of Quantum Matter, South China Normal University, China)
Quantum simulation is a novel method of simulation physical systems with quantum computers. Compared to conventional methods, quantum algorithms have various advantages in doing non-perturvative calculations and real-time evolutions, which makes it very promising to apply them in high energy nuclear physics. We propose a systematic quantum algorithm, which integrates both the hadronic state preparation and the evaluation of real-time light-front correlators. This algorithm can be applied to the calculation of a wide range of quantities in high energy nuclear physics. As a demonstration, we calculate the parton distribution functions, the light-cone distribution amplitudes and scattering amplitudes in the 1+1 dimensional NJL model. The results are qualitatively consistent with QCD calculations.
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
Surface defect in N=4 SYM and integrability
2024年7月17日(水) 16:00 - 17:00
河井 大輝 (Ph.D. Student, University of California, Santa Barbara, USA)
In the N=4 super Yang-Mills theory, it is well-known that the one-loop anomalous dimension operator for the single trace operators is equivalent to an integrable spin chain. Recent works have extended the application of integrability to scenarios involving a BPS boundary or defects such as 't Hooft line. One can describe the correlators of the single trace operators as an overlap between the Bethe state and the corresponding defect state. This overlap can be exactly calculated if the defect state is a so-called integrable state. We show that the state corresponding to the Gukov-Witten surface defect is integrable. We also calculate the tree-level one-point function of the single trace operators and set up the perturbation calculation in this defect background for one-loop corrections.
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
Supernovae as Tracers of Massive-Star Evolution
2024年7月17日(水) 14:00 - 15:15
平松 大地 (Post-Doctoral fellow, Harvard University, USA)
Supernovae are the terminal explosions of massive stars with influences on every astrophysical scale. Advanced wide-field and high-cadence transient surveys routinely discover supernovae near the moment of explosion. Coupled with prompt and continuous follow-up facilities, these observations have revealed unprecedented features of dense circumstellar medium in various spatial scales as traced by the expanding supernova ejecta. Such circumstellar medium is thought to originate from mass-loss activities in the final years to decades of stellar evolution; however, their inferred densities exceed the expectations from standard theory by many orders of magnitude. In this talk, I will first introduce standard stellar evolution and supernova explosion mechanisms, and then describe novel observational probes and modeling techniques of supernovae interacting with circumstellar medium to reconstruct their explosion properties and progenitor mass-loss histories. Finally, I will discuss our on-going largest sample study of interacting supernovae and emerging pictures of dramatic dying breaths of massive stars.
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
Quantum Error Transmutation
2024年7月17日(水) 10:30 - 11:30
Daniel Zhang (Postdoctoral Fellow, University of Oxford, UK)
We introduce a generalisation of quantum error correction, relaxing the requirement that a code should identify and correct a set of physical errors on the Hilbert space of a quantum computer exactly, instead allowing recovery up to a pre-specified admissible set of errors on the code space. We call these quantum error transmuting codes. They are of particular interest for the simulation of noisy quantum systems, and for use in algorithms inherently robust to errors of a particular character. Necessary and sufficient algebraic conditions on the set of physical and admissible errors for error transmutation are derived, generalising the Knill-Laflamme quantum error correction conditions. We demonstrate how some existing codes, including fermionic encodings, have error transmuting properties to interesting classes of admissible errors. Additionally, we report on the existence of some new codes, including low-qubit and translation invariant examples.
会場: セミナー室 (359号室) 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
Mapping the Phase Space of toric Calabi-Yau 3-folds using Explainable Machine Learning
2024年7月16日(火) 13:30 - 14:30
Rak-Kyeong Seong (Assistant Professor, Department of Mathematical Sciences, Ulsan National Institute of Science and Technology (UNIST), Republic of Korea)
This talk will give a brief introduction on how bipartite graphs on a torus represent 4-dimensional quiver gauge theories and their moduli space which is a toric Calabi-Yau 3-fold - a cone over a Sasaki-Einstein 5-manifold. Under mirror symmetry, the bipartite graph can be identified with the tropical projection of the mirror curve obtained from the Newton polytope associated to the toric Calabi-Yau 3-fold. Changes to the complex structure moduli of the mirror Calabi-Yau determine the overall shape of the bipartite graph on the torus. For certain choices of complex structure moduli, the bipartite graph undergoes a graph mutation which is identified with Seiberg duality of the associated 4-dimensional quiver gauge theory. This talk will discuss recent progress in understanding when such mutations occur from the point of view of Calabi-Yau mirror symmetry with the help of new computational techniques such as machine learning.
会場: セミナー室 (359号室) 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
Topological recursion and twisted Higgs bundles
2024年7月16日(火) 10:30 - 12:00
Christopher Mahadeo (Research Assistant Professor, Department of Mathematics, The University of Illinois at Chicago (UIC), USA)
Prior works relating meromorphic Higgs bundles to topological recursion have considered non-singular models that allow the recursion to be carried out on a smooth Riemann surface. I will discuss some recent work where we define a "twisted topological recursion" on the spectral curve of a twisted Higgs bundle, and show that the g=0 components of the recursion compute the Taylor expansion of the period matrix of the spectral curve, mirroring a result of for ordinary Higgs bundles and topological recursion. I will also discuss some current work relating topological recursion to a new viewpoint of quantization of Higgs bundles.
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
Discovering Physical Laws with Artificial Intelligence
2024年7月12日(金) 10:00 - 11:30
刘 子鸣 (Ph.D. Student, Department of Physics, Massachusetts Institute of Technology, USA)
Deep neural networks have been extremely successful in language and vision tasks. However, their black-box nature makes them undesirable for scientific tasks. In this talk, I will show how we can make these black-box AI models more interpretable and transparent and use them to discover physical laws, including conservation laws (AI Poincare), symmetries, phase transitions and symbolic relations (Kolmogorov-Arnold Networks). Ziming is a physicist and a machine learning researcher. Ziming received BS in physics from Peking Univeristy in 2020, and is current a fourth-year PhD student at MIT and IAIFI, advised by Max Tegmark. His research interests lie generally in the intersection of artificial intelligence (AI) and physics (science in general).
会場: via Zoom
イベント公式言語: 英語
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セミナー
Tensionless Strings in a Kalb-Ramond Background
2024年7月10日(水) 16:00 - 17:00
Ritankar Chatterjee (Ph.D. Student, Indian Institute of Technology Kanpur, India)
We investigate tensionless (or null) bosonic string theory with a constant Kalb-Ramond background turned on. In analogy with the tensile case, we find that the constant Kalb-Ramond field has a non-trivial effect on the spectrum only when the theory is compactified on an S^1 ⊗d background with d ≥ 2. We discuss the effect of this constant background field on the tensionless spectrum constructed on three known consistent null string vacua. We elucidate further on the intriguing fate of duality symmetries in these classes of string theories when the background field is turned on. Based on: https://arxiv.org/abs/2404.01385
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
764 イベント