Koji Harada | Last modified date：2023.06.12 |

Professor /
Graduate School of Science, Department of Physics

Division for Theoretical Natural Science

Faculty of Arts and Science

Division for Theoretical Natural Science

Faculty of Arts and Science

Graduate School

Other Organization

Administration Post

Vice President

Dean of the Faculty of Arts and Science

Director of the Admission Center

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Homepage

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THEORY OF SUBATOMIC PHYSICS AND ASTROPHYSICS .

Phone

092-802-6029

Fax

092-802-6009

Academic Degree

Doctor of Science

Country of degree conferring institution (Overseas)

No

Field of Specialization

Theoretical Elementary Particle Physics

Total Priod of education and research career in the foreign country

03years09months

Outline Activities

Research activity:

In the Standard Model of Elementary Particle Physics, hadrons, which participate in Strong Interactions, are described by the gauge field theory called Quantum Chromodynamics (QCD) and regarded as bound states of quarks and gluons. Due to the Confinement mechanism, quarks and gluons are never observed by themselves and only the composite particles, hadrons, are observed. It is therefore of primary importance to understand QCD bound states to really understand Strong Interactions. However, bound states in a relativistic field theory like QCD are complicated combinations of multi-particle states in which all of the quantum fluctuation scales are coupled: they are really very complicated non-perturbative dynamical systems.

QCD is the "ultimate theory" of Strong Interactions and is expected to be responsible (ultimately) for the (most of) structures and interactions of all hadrons, including various nuclei. It is however extremely difficult to explain the properties of (stable) nuclei directly in terms of QCD. After all, we usually exploit some phenomenological "realistic nuclear forces" to explain the properties, admittedly it is a very retrogressive way from the point of view that we already have the "ultimate theory". Although it is unlikely that we can describe nuclei directly in terms of quark-gluon degrees of freedom, it is worthwhile clarifying what we can say directly from the dynamics of QCD, without recourse to phenomenological models.

Following the idea given above, I study how to describe hadrons by using Effective Field Theory. Effective Field Theory is a framework which has the connection to QCD through chiral symmetry breaking, and allows systematic improvement of the approximation. In particular, I am interested in applying the ideas of Wilsonian Renormalization Group to Nuclear Effective Field Theory to figure out the characteristic features of the dynamics.

I studied high-density nuclear systems at low temperatures, which cannot be investigated in the lattice QCD approach, by using lattice simulations of the Nuclear Effective Field Theory.

Educational activity:

As a member of Faculty of Arts and Science, I am involved very much in education for the freshmen.

I also give seminars and have meetings for the graduates in the group of Theory of Subatomic Physics and Astrophysics beside giving everyday supervision.

In the Standard Model of Elementary Particle Physics, hadrons, which participate in Strong Interactions, are described by the gauge field theory called Quantum Chromodynamics (QCD) and regarded as bound states of quarks and gluons. Due to the Confinement mechanism, quarks and gluons are never observed by themselves and only the composite particles, hadrons, are observed. It is therefore of primary importance to understand QCD bound states to really understand Strong Interactions. However, bound states in a relativistic field theory like QCD are complicated combinations of multi-particle states in which all of the quantum fluctuation scales are coupled: they are really very complicated non-perturbative dynamical systems.

QCD is the "ultimate theory" of Strong Interactions and is expected to be responsible (ultimately) for the (most of) structures and interactions of all hadrons, including various nuclei. It is however extremely difficult to explain the properties of (stable) nuclei directly in terms of QCD. After all, we usually exploit some phenomenological "realistic nuclear forces" to explain the properties, admittedly it is a very retrogressive way from the point of view that we already have the "ultimate theory". Although it is unlikely that we can describe nuclei directly in terms of quark-gluon degrees of freedom, it is worthwhile clarifying what we can say directly from the dynamics of QCD, without recourse to phenomenological models.

Following the idea given above, I study how to describe hadrons by using Effective Field Theory. Effective Field Theory is a framework which has the connection to QCD through chiral symmetry breaking, and allows systematic improvement of the approximation. In particular, I am interested in applying the ideas of Wilsonian Renormalization Group to Nuclear Effective Field Theory to figure out the characteristic features of the dynamics.

I studied high-density nuclear systems at low temperatures, which cannot be investigated in the lattice QCD approach, by using lattice simulations of the Nuclear Effective Field Theory.

Educational activity:

As a member of Faculty of Arts and Science, I am involved very much in education for the freshmen.

I also give seminars and have meetings for the graduates in the group of Theory of Subatomic Physics and Astrophysics beside giving everyday supervision.

Research

**Research Interests**

- Dynamical properties of the cosmological first-order phase transition

keyword : false vacuum, phase transition, origin of the baryon asymmetry of the Universe, dark matter

2022.04. - Lattice simulations of finite-density nucleon systems based on nulear effective field theory

keyword : lattice theory, effective field theory, numerical simulations

2013.10～2017.03. - Application of nonperturbative renormalization group methods to three-body systems

keyword : renormalization group, limit cycle, Efimov effect

2011.08～2013.05. - Application of effective field theory to nuclear reactions

keyword : effective field theory, nuclear reactions

2008.09～2009.03We consider the applications of effective field theory to nuclear reactions at intermediate energies.. - Apparently noninvariant terms in field theory with nonlinearly realized symmetries

keyword : nonlinear sigma models, radiative corrections, perturbation theory

2008.05～2009.08There emerge apparently noninvariant terms in nonlinearly realized field theories, such as nonlinear sigma models, in the effective potential calculated perturbatively. The emergence of such terms do not imply that the symmetry is lost. We show that such a phenomenon is a general feature and why they emerge.. - Renormalization group analysis for the $V_{low k}$ potential

keyword : renormalization group, effective interactions, nuclear forces

2007.08～2008.04We pointed out that there are problems in the derivations of the renormalization group equation given in the literature for the so-called V_{low k} effective potential for the nuclear forces.. - Wilsonian Renormalization Group and Nuclear Effective Field Thoery

keyword : renormalization, effective field theory, nontrivial fixed point, power counting

2004.04We analyze the behavior of Nuclear Effective Filed Theory(NEFT),which describe the interactions of nucleons at low energies, by using Wilsonian Renormalization Group. In particular, we determine the power counting of NEFT by the scaling dimensions of the operators.. - An Effecitive Theory Approach to Skyrme Model and Application to Pentaquarks

keyword : Skyrme model, pentaquark

2003.02～2004.10We develop a new approach to Skyrme model based on the most general chiral effective theory of mesons. The theory contains a set of new interactions, which have never been considered. Based on this new theory, we compute some properties, such as masses and decay widths, of the recently discovered pentaquarks.. - Large-$N_c$ QCD and nontriviality of low-energy effective field theory

keyword : large-N_c, QCD, effective field theory, renormalization, renormalization group

2001.07The purpose of the research is to show that it is possible to understand the "unnatural" bahaviors in the low-energy region of strong interactions in the light of $1/N_c$ expansion..

**Academic Activities**

**Papers**

**Membership in Academic Society**

- The Physics Education Society of Japan
- American Association of Physics Teachers
- The Physical Society of Japan

**Awards**

- Quantization of anomalous gauge theory

Educational

**Educational Activities**

At the Graduate School:

・Seminars on Elementary Particle Physics I (2001, 2005, 2010, 2013)

・Gauge Theory (2003, 2004, 2005, 2006, 2nd semester)

・Topics in Elementary Particle Physics (2007, 2008, 2009, 2010, 2011 2nd semester)

・Quantum Field Theory (2012,2013 1st semester)

・Elementary Particle Theory (2015 2nd semester(1/3), 2017 2nd semester)

・various kinds of study meetings in the lab.

At the Undergraduate School:

・Exercises in Electromagnetism (2000, 1st semester)

・Exercises in Physics (1/2) (2000, 1st semester)

・Frontier in Physics (particle physics part) (2000, 2001, 2002, 1st semester)

・Mechanics II (2002, 2003, 2004, 2005, 2006, 1st semester)

・Current Topics in Physics (particle physics part) (2002, 2003, 2004, 2011, 1st semester)

・Core Seminar (2006, 1st semester)

・Seminars in Physics I, II (2002, 2003, 2006, 2007, 2008, 2011, 2012)

・General Relativity (2003, 2004, 2005, 2006, 2007, 2nd semester; 2009, 2010, 2011 1st semester)

・Analytical Dynamics and Exercises (2007, 2008, 2009, 2010, 2011, 2012, 2013 1st semester)

・Quantum Mechanics II (2012,2013 1st semester)

At the Common Education:

・Fundamental Experiments in Physics (2000, 1st semester)

・Elementary Classical Mechanics and Exercises I (2002, 1st semester)

・Elementary Classical Mechanics and Exercises II (2000, 1st semester, 2001, 2002, 2nd semester)

・Elementary Classical Mechanics (2001, 1st semester)

・Elementary Electromagnetism (2001, 2002, 1st semester, 2001, 2nd semester)

・Heat and Waves (2001, 1st semester)

・Our Material World (1/4) (2002, 2004(twice), 2006, 1st semester)

At the KIKAN Education:

・KIKAN-Education Seminar ((2 classes)2014, （１ class)2015, (1 class)2016 1st semester),((1 class)2017,(1 class)2018,(1 class)2019, (1 class)2020, (1 class)2021, (2 classes)2022, summer quarter)

・Physics in Everyday Life (2014, 2015, 2016, 1st semester)

・Physics in Everyday Life A (2017,2018,2019,2020,2021, 2022, spring quarter, 2017,2018,2019,2020,2021,2022 winter quarter)

・Fundamental Physics IB (2014, 2015, 2016, 2017, 2018, 2019,2020, 2nd semester)

・Interdisciplinary Collaborative Learning of Social Issues A （２０１６ 1st semester), （2014, 2015, 2016, 2017 2nd semester)

・Hands-on Natural Science (2017,2018 autumn&winter quarters)

・Seminar -- How to write clearly -- (2015, 1st semester)

・"Understanding" and "Easy to understand" (2018, 2019,2020,2021, autumn quarter)

・"Let's get hands on a math toolbox" (2021, 2022 summer quarter)

As for special sets of lectures:

・Introduction to Elementary Particle Physics (at Fukuoka University)

・Elementary Particles and Symmetries (at Fukuoka University)

・Nonrelativistic Scattering Theory (at Ehime University)

・Relativity (at Kagoshima University)

・Seminars on Elementary Particle Physics I (2001, 2005, 2010, 2013)

・Gauge Theory (2003, 2004, 2005, 2006, 2nd semester)

・Topics in Elementary Particle Physics (2007, 2008, 2009, 2010, 2011 2nd semester)

・Quantum Field Theory (2012,2013 1st semester)

・Elementary Particle Theory (2015 2nd semester(1/3), 2017 2nd semester)

・various kinds of study meetings in the lab.

At the Undergraduate School:

・Exercises in Electromagnetism (2000, 1st semester)

・Exercises in Physics (1/2) (2000, 1st semester)

・Frontier in Physics (particle physics part) (2000, 2001, 2002, 1st semester)

・Mechanics II (2002, 2003, 2004, 2005, 2006, 1st semester)

・Current Topics in Physics (particle physics part) (2002, 2003, 2004, 2011, 1st semester)

・Core Seminar (2006, 1st semester)

・Seminars in Physics I, II (2002, 2003, 2006, 2007, 2008, 2011, 2012)

・General Relativity (2003, 2004, 2005, 2006, 2007, 2nd semester; 2009, 2010, 2011 1st semester)

・Analytical Dynamics and Exercises (2007, 2008, 2009, 2010, 2011, 2012, 2013 1st semester)

・Quantum Mechanics II (2012,2013 1st semester)

At the Common Education:

・Fundamental Experiments in Physics (2000, 1st semester)

・Elementary Classical Mechanics and Exercises I (2002, 1st semester)

・Elementary Classical Mechanics and Exercises II (2000, 1st semester, 2001, 2002, 2nd semester)

・Elementary Classical Mechanics (2001, 1st semester)

・Elementary Electromagnetism (2001, 2002, 1st semester, 2001, 2nd semester)

・Heat and Waves (2001, 1st semester)

・Our Material World (1/4) (2002, 2004(twice), 2006, 1st semester)

At the KIKAN Education:

・KIKAN-Education Seminar ((2 classes)2014, （１ class)2015, (1 class)2016 1st semester),((1 class)2017,(1 class)2018,(1 class)2019, (1 class)2020, (1 class)2021, (2 classes)2022, summer quarter)

・Physics in Everyday Life (2014, 2015, 2016, 1st semester)

・Physics in Everyday Life A (2017,2018,2019,2020,2021, 2022, spring quarter, 2017,2018,2019,2020,2021,2022 winter quarter)

・Fundamental Physics IB (2014, 2015, 2016, 2017, 2018, 2019,2020, 2nd semester)

・Interdisciplinary Collaborative Learning of Social Issues A （２０１６ 1st semester), （2014, 2015, 2016, 2017 2nd semester)

・Hands-on Natural Science (2017,2018 autumn&winter quarters)

・Seminar -- How to write clearly -- (2015, 1st semester)

・"Understanding" and "Easy to understand" (2018, 2019,2020,2021, autumn quarter)

・"Let's get hands on a math toolbox" (2021, 2022 summer quarter)

As for special sets of lectures:

・Introduction to Elementary Particle Physics (at Fukuoka University)

・Elementary Particles and Symmetries (at Fukuoka University)

・Nonrelativistic Scattering Theory (at Ehime University)

・Relativity (at Kagoshima University)

**Other Educational Activities**

- 2010.03, Lectures at Shinshu Winter School 2010.

Social

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