Past Seminars

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, Waki, 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).

PDF not available

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
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