Past Advanced Seminars (Advanced Seminars)

Title: Non-equilibrium physics

Lecturer: Ryo Hanai, Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University
Date: October, 2023

Phase transitions occur ubiquitously in nature, both in and out of equilibrium. In this lecture, I aim to give an overview of nonequilibrium phase transitions with an emphasis on what are the differences to their equilibrium counterparts. I will introduce the basics of non-equilibrium field theories that are used as a powerful tool to understand those phases. I will analyze several examples of nonequilibrium states/phase transitions such as flocking and non-reciprocal phase transitions.

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Title: Non-reciprocal frustration physics

Lecturer: : Ryo Hanai, Assistant Professor, Yukawa Institute for Theoretical Physics, Kyoto University
Date: October, 2023

Having conflicting goals often leads to frustration. The conflict occurs, for example, in systems that cannot simultaneously minimize all interaction energy between the constituents, a situation known as geometrical frustration. A typical feature of these systems is the presence of accidental ground state degeneracy that gives rise to a rich variety of unusual phenomena such as order-by-disorder and spin glasses. In this talk, I will show that a dynamical counterpart of these phenomena may arise from a fundamentally different, non-equilibrium source of conflict: non-reciprocal interactions [1]. I will show that non-reciprocal systems with anti-symmetric coupling generically generate marginal orbits that can be regarded as a dynamical counterpart of accidental degeneracy, due to the emerging Liouville type theorem. These “accidental degeneracies” of orbits are shown to often get “lifted” by stochastic noise or weak random disorder to give rise to order-by-disorder phenomena with the peculiarity that the emerging state usually has a time crystalline order. I further report numerical evidence of a non-reciprocity-induced spin-glass-like state that exhibits aging and a power-law temporal relaxation associated with a short-ranged spatial correlation. This work provides an unexpected link between the physics of complex magnetic materials and non-reciprocal matter. [1] R. Hanai, arXiv:2208.08577.

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Title: What's the matter with antimatter? -Science and technology of antimatter-

Lecturer: Makoto C. Fujiwara, Senior Research Scientist, TRIUMF, Canada
Date: May, 2023

The existence of antimatter was first predicted by Dirac in 1928. The antielectron, now called the positron, and the antiproton were experimentally discovered in 1932 and 1955, respectively. However, it took more than half a century for physicists to create and control the atomic form of antimatter, the antihydrogen atom, in sufficient quantity to study its properties. Studying antihydrogen has important implications for our understanding of fundamental physics. The hydrogen atom, being the simplest atomic system, has played a central role in the development of modern physics. By studying its antimatter counterpart, antihydrogen, we can precisely probe the fundamental symmetries between matter and antimatter. In this seminar, I will discuss the production, manipulation, and recent measurements of antihydrogen atoms "bottled" in the ALPHA antihydrogen trap at CERN. I will also describe our ongoing effort to measure the gravitational force on antimatter by "dropping" antihydrogen atoms. Additionally, I will touch upon our new project at TRIUMF, named HAICU, which aims to develop quantum sensing techniques applicable to antimatter.

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Title: Mechanical structure of hadrons

Lecturer: Hyun-Chul Kim, Professor, Inha University, Korea
Date: December, 2022

In the present talk, we review recent works on the gravitational form factors (GFFs) of hadrons and the corresponding energy-momentum tensor densities. We start from the GFFs of the pion and show how the Gell-Mann-Oakes-Renner relation secures the stability of the pion. We then discuss the EMT densities of the nucleon, emphasizing the D-term form factor, and pressure and shear-force densities. We also discuss the physical implications of the pressure and shear-force densities in the context of nucleon stability. We extend the studies to the baryon octet, where the effects of flavor SU(3) symmetry come into play. We discuss the numerical results and draw conclusions.

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Title: Material Learning

Lecturer: Wilfred G. van der Wiel, Professor, University of Twente, The Netherlands
Date: November, 2022

Our goal is to develop intelligent matter and systems/devices based on it for information processing. Intelligent matter in this context is defined as matter that incorporates sensing, actuation, feedback (network property) and long-term memory, enabling learning1. In particular, we focus on disordered ("designless") nanoscale material networks that exhibit complex behavior in the form of a tunable nonlinear electronic response. By using a multi-terminal layout, we are able to apply multiple input, output and configuration signals. While the systems do not exhibit any a priori functionality, through the process of material learning, we will realize the desired functionality a posteriori. By exploiting the nonlinearity of a nanoscale network of boron dopants in silicon, referred to as a dopant network processing unit (DNPU), we can significantly facilitate classification. Using a convolutional neural network approach, it becomes possible to use our device for handwritten digit recognition2. An alternative material learning approach is followed by first mapping our DNPU on a deep-neural-network model, which allows for applying standard machine-learning techniques in finding functionality3. Finally, we show that kinetic Monte Carlo simulations of electron transport in DNPUs can be used to reproduce the main characteristics and to depict the charge trajectories4. [1] C. Kaspar et al., Nature 594, 345 (2021). [2] T. Chen et al., Nature 577, 341 (2020). [3] H.-C. Ruiz Euler et al., Nature Nanotechnol. 15, 992 (2020). [4] H. Tertilt, J. Bakker, M. Becker, B. de Wilde et al., Phys. Rev. Appl. 17, 064025 (2022).

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Title: Exotic Rotations and Vibrations in Nuclei

Lecturer: Umesh Garg, Professor, Department of Physics, University of Notre Dame, Indiana, USA
Date: February, 2022

The nucleus is an ensemble of fermions, too many in number for all its constituents to be treated individually, yet too few for the system to be treated purely statistically. Its properties can be attributed, in some cases, to individual particles, but many nuclear properties can be described by treating the nucleus as a "collective" unit, of both spherical and non-spherical shapes. Among the common phenomena spanning the "collective" behavior are rotation and vibration, both manifesting themselves as band structures (cascades of gamma-ray transitions of specific types) in the level scheme of the nuclei. In this course, we will learn about these phenomena, with emphasis on some exotic aspects: large-scale nuclear vibrations -the giant resonances- and their connection to nuclear incompressibility and astrophysical phenomena like neutron stars and their mergers; exotic quantal rotation of nearly spherical nuclei resulting in magnetic and anti-magnetic rotational bands; and, motion of triaxial nuclei, giving rise to nuclear chirality (handedness), and wobbling motion (akin to the classical motion of an asymmetric top). Outline: 1. Basics of the Nuclear Collective Model 2. Collective Vibrations: Giant Resonances 3. Collective Vibrations: Nuclear Incompressibility 4. Collective Rotations: Antimagnetic Rotation, Chirality 5. Collective Rotations: Wobbling 6. Seminar: Does nuclear incompressibility depend on nuclear structure? 7. Student presentations

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Title: Recent developments of nonequilibrium physics in quantum many-body systems

Lecturer: Naoto Tsuji, Associate Professor, Department of Physics, Graduate School of Science, The University of Tokyo
Date: July, 2021

Nonequilibrium physics of quantum many-body systems is a frontier of condensed matter physics that offers various opportunities to realize new phases of matter and various theoretical challenges to understand them. The field has been motivated by recent advances in experiments to observe ultrafast dynamics of quantum many-body systems in solid materials, cold atoms, and so on. In fact, recent studies have uncovered a rich variety of exotic states that cannot be accessed in (or near) equilibrium, including Floquet topological phases, Higgs mode in superconductors, and quantum many-body scars. In this intensive course, we will review these recent developments of nonequilibrium physics in quantum many-body systems, mainly from a theoretical point of view. Outline: 1. Introduction to nonequilibrium physics in quantum many-body systems 2. Floquet theory for periodically driven quantum systems 3. Nonequilibrium superconductors and Higgs mode 4. Thermalization in isolated quantum systems 5. Quantum many-body scars 6. Open quantum systems, non-Hermitian systems

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Title: Quantum phenomena in semiconductor low dimensional systems & nanostructures and their applications

Lecturer: David Guy Austing, Senior Research Officer, National Research Council, Canada
Date: November, 2020

Semiconductor nanostructures provide intriguing platform to manifest the quantum mechanical effects and to realize their electrical controls. Up to now, rich physical phenomena such as control of single quantum and quantum many-body effects have been studied. In particular, electron spin in a semiconductor quantum dot is a good quantum two-level system. After the proposal of a qubit using the electron spin, detection, manipulation of single electron spins and two-qubit operation have been realized and the development of quantum computers is remarkable. In this focused lecture, the physics of semiconductor low dimensional systems including quantum dots and the current status of the research of quantum information processing using electron spins are reviewed. Contents: 1. Introduction 2. Quantum transport in semiconductor low dimensional systems 3. Semiconductor quantum dots 4. Detection, manipulation, spin relaxation and spin coherence of single electrons in semiconductor quantum dots 5. Application to quantum computers

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Title: Supersymmetric field theories and written index

Lecturer: Seok Kim, Professor, Department of Physics and Astronomy, Seoul National University
Date: July, 2020

I will explain our microscopic understanding of black hole thermodynamics in the holographic quantum gravity in anti de Sitter (AdS) spacetime, using a quantum field theory approach. Our key examples are the so-called BPS black holes in AdS5 x S5, which can be studied using the Witten index of 4 dimensional maximally supersymmetric Yang-Mills theory. In the first five lectures, the details will be comprehensively explained or motivated from scratch (from basic concepts to the signs/factors/notations). In the last lecture (seminar), we will discuss more technical advances in BPS AdS_D black holes at D=4,6,7, with an emphasis on gauge dynamics in various dimensions. Outline of the lectures: 1. Introduction: black hole thermodynamics, AdS black holes, QFT duals 2. The index of 4d N=4 Yang-Mills theory 3. Cardy limit and large black holes 4. Numerical approach 5. Anomaly-based approach 6. Seminar: AdS black holes in various dimensions

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Title: Statistical mechanics in quantum annealing

Lecturer: Masayuki Ohzeki, Associate Professor, Tohoku University
Date: September, 2019

Do you know quantum annealing? This is proposed as a solver of optimization problems by use of quantum fluctuation. Recently, as a solver, the method is well known by many Japanese media reports. In addition, the D-Wave Systems implements the method by use of the superconducting qubits, namely quantum annealer. Therefore, we test the quantum annealing by real experiments without numerical simulations following quantum mechanics. We observe the behavior of several spin models by use of the quantum annealer. In this course, we investigate the properties of the spin models by the D-Wave quantum annealer as experiments and reproduce the results by theoretical assessment through the prescription of statistical mechanics. Furthermore, we show some applications of the quantum annealer for solving optimization problems and performing machine learning. Class Plan: 1. Basics of quantum annealing. 2. How to use quantum annealer. (PC demonstration by students themselves) 3. Solving several Ising models 4. Phase transition 5. Comparison with results by statistical mechanics 6. Solving optimization problems 7. Boltzmann machine learning Textbooks: Printed matter in lecture (PDF) Elements of Phase Transitions and Critical Phenomena (Oxford Graduate Texts) (English Edition) Hidetoshi Nishimori and Gerardo Ortiz

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Title: The structure of exotic nuclei

Lecturer: Kathrin Wimmer, Associate Professor, Department of Physics, Graduate School of Science, The University of Tokyo
Date: May, 2019

This course gives an overview of nuclear physics with an emphasis on exotic nuclei. Each lecture will start with an introduction to the topic and in the latter half address recent progress and new developments in the field. Experimental and theoretical tools and techniques will also be introduced. Outline: 1. General properties of nuclei, radii, masses 2. Decay 3. Nuclear models: single-particle properties and collective motion 4. Nuclear reactions 5. Gamma-ray spectroscopy 6. Nuclear astrophysics 7. Seminar "Coulomb excitation of mirror nuclei: testing iso-spin symmetry”

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Title: Computational physics: Introduction to numerical calculations

Lecturer: Yoshi Uchida, Reader, Imperial College London, London, UK
Date: January, 2018

Computational methods have never been more important in physics research, and indeed many recent advances in computing owe themselves to the needs of modern physics experiments. While many areas of research and commerce require the use of computers, the need for numerical rigour alongside the ability to perform number-crunching at unprecedented rates makes it important that modern physicists have a good understanding of the underlying principles behind numerical methods. We will cover all essential aspects of numerical methods, and therefore this course will be useful for students in any area of physics. After taking this course, students will be able to understand the foundations upon which modern computing techniques, such as machine learning, are based. Students may use any programming language of their choice to follow this course.

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Title: Dirac physics at surfaces and ultrathin materials

Lecturer: Toru Hirahara, Associate Prof., Tokyo Institute of Technology, Tokyo, Japan
Date: November, 2016

It is needless to point out the importance of clarifying the electronic structure of materials in understanding their physical properties. In this intensive course, the peculiar properties of Dirac electrons that arise from their linear band dispersion will be introduced. Emphasis will be placed on Dirac electrons at surfaces of topological insulators or ultrathin materials such as graphene. Description of sample fabrication and experimental techniques as well as theoretical concepts will be presented starting from the basic of solid state physics.

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Title: Quantum information, Black Holes, and Holography

Lecturer: Beni Yoshida, Dr., Perimeter Institute, Ontario, Canada
Date: September, 2016

In recent years, we have seen that quantum information theory provides a powerful tool to deepen our understanding of quantum field theory and quantum gravity. This course aims at encouraging interactions between high energy physics and quantum information theory community by covering basics of quantum information theory as well as reviewing some of recent important progresses.

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Title: The next decade of neutrino physics (a biased view)

Lecturer: Karol Lang, Professor, The University of Texas at Austin, USA
Date: December, 2015

The last two decades have brought a remarkable progress in neutrino physics. Experiments have demonstrated that neutrinos oscillate, thus have mass, and determined most of their mixing parameters, including the three mixing angles and two mass splittings. Despite these successes, some of the key neutrino questions like the CP phase of the mixing matrix, the neutrino mass ordering or precise values of mixing angles, remain elusive and require extraordinary sensitivities of future experiments. The oscillations measurements further motivate studies of properties of neutrinos including investigating if they are a Majorana or a Dirac-type. Natural conjectures suggest that deeper understanding of neutrinos may provide a glimpse onto phenomena at a Planck-scale energy level, would broaden our knowledge of fundamental forces, may shed light onto the baryon asymmetry, and can improve our understanding of the evolution of the Universe. Finally, there are experimental hints suggesting existence of sterile neutrinos that would expand the three-neutrino paradigm. We will briefly and selectively discuss experimental programs underway that will elucidate on all these fundamental questions of neutrinos and particle physics.

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Title: Introduction to strongly-correlated material science: transition metal oxides and molecular conductors

Lecturer: Hitoshi Seo, Senior Research Scientist, RIKEN, Wako, Japan
Date: November, 2015

Strongly-correlated materials such as transition metal oxides and molecular crystals show a rich variety of physical properties. Phase transitions between different states of matter are observed, which can change the properties of materials sometimes drastically, in terms of electronic, magnetic, and structural outcomes. Metal-insulator transition is one of the drastic phenomena, where the electron-electron interaction drives the system overcoming the kinetic energy of the electrons. This is in contradiction with the band theory, i.e. the standard theory in solid state physics, therefore we face a fundamental challenge in condensed matter physics to understand them. In this course, we first introduce the materials and their properties, especially focusing on Mott transition and charge ordering, both as typical and heavily-studied systems showing the metal-insulator transition; then we explain the basic problem that is the failure of the band theory to explain experimental facts. Theoretical tools will be introduced and numerical approaches will be mentioned. Finally selected topics will be briefly presented in connection with experiments (possible topics include quantum spin-liquid, charge frustration, and photo-induced charge-order melting).

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Title: Introduction to Particle Physics beyond the Standard Model

Lecturer: Adam Pawel Falkowski, Professor, Laboratoire de Physique, Paris, France
Date: May, 2014

The goal of this lecture series is to give an overview of the current research in particle physics beyond the Standard Model. First, I will review the current theory of fundamental interactions known as the Standard Model. This theory has successfully passed an immense number of experimental tests in high-energy colliders and low-energy precision experiments. The last crucial prediction - the existence of a scalar particle known as the Higgs boson - was spectacularly confirmed 2 years ago by the experiments at the Large Hadron Collider. Yet we know that the Standard Model is not the ultimate theory of fundamental interactions. The information from neutrino oscillation experiments and from observations of the large-scale universe forces us to consider extensions of the Standard Model. I will summarize these phenomenological reasons as well as some theoretical motivations to go beyond the Standard Model. Then I will explain in more detail how one can extend the Standard Model to explain the existence of dark matter in the universe, and to account for a period of accelerated expansion at the early stage of the universe known as inflation. Finally, I will discuss how the Standard Model can be tested in the current and future high-energy colliders, and what kind of new particles and interactions we are hoping to find there.

Title: Optical processes in nanostructures

Lecturer: Junichiro Kono, Professor, Rice University, Texas, USA
Date: October, 2013

Optical Processes in Nanostructures. THz Phenomena in Carbon Nanomaterials. Ultrafast Optical Phenomena in Carbon Nanomaterials. High Magnetic Field Phenomena in Carbon Nanotubes. Coherent Optical Phenomena in Semiconductor Quantum Wells.

Title: Introduction into strong field QED on the computer

Lecturer: Hartmut Ruhl, Professor, Ludwig-Maximilians University, Munich, Germany
Date: May, 2012

The topical seminar has the intent to first explain the scientific case, then to develop the required theoretical framework to understand the science case, and finally to introduce into numerical aspects of the problem.

Title: Computational studies on high temperature superconductivity

Lecturer: Kazuhiko Kuroki, Professor, University of Electro-Communication, (UEC), Tokyo
Date: December 16, 2011: Time: 1:00-2:30 3:00-4:30 (with 30 min. break)

Superconductivity is a phenomenon in which the resistivity disappears at a certain transition temperature Tc. In conventional superconductors, Tc is as low as (O(10K), but in the past quarter of a century, two families of high Tc superconductors, cuprates (max Tc~150K) and the iron pnictides (max T~55K), have been discovered. It is widely believed that theoretical understanding of these materials can lead to finding new, even higher Tc materials. In the present lecture, we start with some basic learning on solid state physics and superconductivity in the first half. In the second half, some of the essential experimental observations of the actual high Tc materials are presented, and the lecture will focus on how these experiments can be understood through computational approaches based on model Hamiltonians. Finally, a possible way of reaching even higher Tc is discussed.

Title: Journey to the Wonderful World of Quantum Electrodynamics

Lecturer: Alexander TITOV, Dubna, Russia
Date: July 22, 2011 Time: 4:30-6:30PM (Lecture: 90 min., Q&A 30 min.)

The aim of our lecture is to make a journey to the impressive world of Quantum Electrodynamics (QED). QED, being the relativistic quantum field theory, describes how light and matter interact and it is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electrodynamics giving a complete account of matter and light interaction. In technical terms, QED can be described as a perturbation theory of the electromagnetic quantum processes. We plan to show how to derive the equations of QED from the Lagrange formalism, the appearance of the spin/magnetic moment of electrons, the prediction of anti-particles. Then we will formulate the Feynman rules for the evaluation of the amplitudes of physical processes and illustrate how to apply them to calculations of probabilities of elastic photon-electron scattering (Compton scattering) and electron-positron creation in photon-photon interaction (Breit-Wheeler process) in a second order of perturbation theory. We will also discuss di-muon production in interaction of photons and electrons with atomic nuclei. Then we will move to the non-perturbative solution of QED. We will derive solution of Dirac equation in a (strong) electromagnetic (EM) field of a plane wave (Volkov solution). Such a strong EM field may be interpreted as a field of laser radiation. We will show that in such a field the properties of the electron are changed drastically. The electron mass increases and its three-momentum transforms to the quasi-momentum. The quantum mechanical processes are also modified significantly. As examples, we will show how such modifications apply to photon and neutrino emissions by electron in a strong EM field, to electron-positron production in interaction of photon with strong laser fields, and to particle-decay properties. All these effects are relatively new, but they are widely discussed now, and, hopefully, they will shed light on the non-trivial, non-perturbative effects of QED.

Title: Physics of Core-Collapse Supernovae

Lecturer: Kohsuke SUMIYOSHI, Numazu College of Technology and Theory Group at KEK
Date: July 11, 2011 Time: 4:30-6:30PM (Lecture: 90 min., Q&A 30 min.)

Core collapse supernovae are one of the most energetic phenomena in astronomy and physics. Supernovae occur as a consequence of the gravitational collapse of massive stars of about 20 solar masses at the end of stellar evolution. The supernova explosion mechanism is still unknown after more than four decades of investigations. In this lecture, I introduce the broad and interesting features of core-collapse supernovae and describe the physics at extreme conditions inside supernova cores. I will try to explain the role of hot and dense matter in the dynamics and to demonstrate that the neutrino emission is one of the essential aspects for the explosion as well as the observation. I would also like to talk about the numerical challenge of supernova simulations on high-performance supercomputers.

Title: The Physics of Complexity

Lecturer: Zhensho YOSHIDA, The University of Tokyo
Date: June 27, 2011 Time: 4:30-6:30PM (Lecture: 90 min., Q&A 30 min.)

In the history going back to Galilei and Newton, physics gained triumphs in describing the "cosmos"---the periodic movements of planets and similar regular motions in various systems. However, we have yet to write the theory of the other form of motion ---a more general actuality of events in nature and society that is the so-called "chaos". We must speak of what the theories of sciences have understood; we must speak of the limits of their legitimacy; we shall have to speak of what these theories are leaving in abeyance. Then, and only then, we can determine the realm in which the cosmos and chaos are not disjunct: the complexity is not eliminated from the scope of studies. Beneath the complexity of actual phenomena, there is a mathematical structure that is called nonlinearity---this is the main theme of this lecture. The term nonlinear is worded by a negation form ---it is not a descriptive (deistic) word characterizing a particular property, but it is a distinctive word indicating opposition to linear. The meaning of nonlinear is infinitely wide as a vague area, and is not bound to a concrete frame. Therefore, when we say "mathematical structure that is nonlinear", we do not mean that there is a prescribed structure giving a framework of the theory, but we are paying attention to the unboundedly developing differences from linearity. We will critically analyze the structure of linear theory and reveal its limitations. By this process, the meaning of nonlinear (and, simultaneously, linear) will become more clear and precise. It is hoped that partly through these arguments, the complexity that linear theory has abandoned might be revived on the horizon of science.

[from Z. YOSHIDA, Nonlinear Science-the challenge of complex systems (Springer, 2010)]

Department of Physics, Graduate School of Science
Osaka University, 1-1 Machikaneyama, Toyonaka 560-0043, Osaka, Japan