Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Koji Harada Last modified date:2019.06.06

Professor / Graduate School of Sciences, Department of Physics / Division for Theoretical Natural Science / Faculty of Arts and Science

1. Typical misconception in mechanics that students with majors in the schools of humanities have, probed with force concept inventory (FCI) test.
2. Koji Harada, Satoru Sasabe, Masanobu Yahiro, Numerical study of renormalization group flows of nuclear effective field theory without pions on a lattice, Physical Review C, 10.1103/PhysRevC.94.024004, 94, 024004-1-085006-13, 2016.08, We formulate the next-to-leading order nuclear effective field theory without pions in the two-nucleon sector on a spatial lattice, and investigate nonperturbative renormalization group flows in the strong coupling region by diagonalizing the Hamiltonian numerically. The cutoff (proportional to the inverse of the lattice constant) dependence of the coupling constants is obtained by changing the lattice constant with the binding energy and the asymptotic normalization constant for the groundstate being fixed. We argue that the critical line can be obtained by looking at the finite-size dependence of the groundstate energy. We determine the relevant operator and locate the nontrivial fixed point, as well as the physical flow line corresponding to the deuteron in the two-dimensional plane of dimensionless coupling constants. It turns out that the location of the nontrivial fixed point is very close to the one obtained by the corresponding analytic calculation, but the relevant operator is quite different. .
3. Koji Harada, Hirofumi Kubo, Issei Yoshimoto, Wilsonian renormalization group analysis of nonrelativistic three-body systems without introducing dimerons, Physical Review D, 10.1103.PhysRevD.87.08500, 87, 085006-1-085006-19, 2013.04, Low-energy effective field theory describing a nonrelativistic three-body system is analyzed in the
Wilsonian renormalization group method. No effective auxiliary field (dimeron) that corresponds to two-
body propagation is introduced. The Efimov effect is expected in the case of an infinite two-body
scattering length and is believed to be related to the limit cycle behavior in the three-body renormalization
group equations (RGEs). If the one-loop property of the RGEs for the nonrelativistic system without the
dimeron field, which is essential in deriving RGEs in the two-body sector, persists in the three-body sector,
it appears to prevent the emergence of limit cycle behavior. We explain how the multiloop diagrams
contribute in the three-body sector without contradicting the one-loop property of the RGEs and derive the
correct RGEs, which lead to the limit cycle behavior. The Efimov parameter, s_0, is obtained within a few
percent error in the leading orders. We also remark on the correct use of the dimeron formulation. We find
rich renormalization group flow structure in the three-body sector. In particular, a novel nontrivial fixed
point of the three-body couplings is found when the two-body interactions are absent. We also find, on the
two-body nontrivial fixed point, the limit cycle is realized as a loop of finite size in the space of three-body
coupling constants when terms with derivatives are included..
4. Koji Harada, Hirofumi Kubo, Tatsuya Sakaeda, Yuki Yamamoto, Wilsonian RG analysis of the P-wave Nucleon-Nucleon Scattering Including Pions, 10.1007/s00601-012-0541-9, 2012.09, We perform a Wilsonian renormalization group analysis for the nucleon–nucleon scattering in the
P waves in the nuclear effective field theory including pions, in a similar way to the one done for the S-waves
in our previous paper. We emphasize that the one-pion exchange interaction with large momentum transfer is
of the same order as the leading contact interaction, so that there is no mismatch of the power counting. It is
explicitly shown by obtaining consistent sets of renormalization group equations, that the cutoff dependence
generated by the loop diagrams containing pion exchanges can be compensated by the cutoff dependence of
the coupling constants of the contact interactions..
5. Hirofumi Kubo, Koji Harada, Tatsuya Sakaeda, Yuki Yamamoto, Practical calculational scheme implementing the Wilsonian RG results for nuclear effective field thoery including pions, Few Body Systems, 10.1007/s00601-012-0349-7, 54, 245-249, 2012.03, On the basis of the Wilsonian renormalization group (WRG) analysis of nuclear effective field
theory (NEFT) including pions, we propose a practical calculational scheme in which the short-distance part
of one-pion exchange (S-OPE) is removed and represented as contact terms. The long-distance part of one-
pion exchange (L-OPE) is treated as perturbation. The use of dimensional regularization (DR) for diagrams
consisting only of contact interactions considerably simplifies the calculation of scattering amplitude and
the renormalization group equations. NLO results for nucleon-nucleon elastic scattering in the S-waves are
obtained and compared with experiments. A brief comment on NNLO calculations is given..
6. Koji Harada, Hirofumi Kubo, Yuki Yamamoto, Pions in nuclear effective field theory: how they behave differently at different scales and how they decouple at very low energies, Few Body Systems, 10.1007/s00601-012-0348-8, 54, 239-243, 2012.03, We explain how the Wilsonian renormalization group (RG) can determine the power counting of the
nuclear effective field theory (NEFT) including pions. We emphasize that the separation of pion exchange into
the short-distance part and the long-distance part is essential since they behave differently in the RG analysis;
we found that the latter is perturbative whereas the a part of the former is nonperturbative. As for the contact
interactions power counting turns out to be the same as that for pionless NEFT: pion exchange does not affect
the scaling property of contact operators. Our RG equations for NEFT including pions connect smoothly with
those for the pionless NEFT: pions decouple at very low energies as we expect..
7. Koji Harada, Pions are neither perturbative nor nonperturbative: Wilsonian renormalization-group analysis of nuclear effective field theory including pions, Physical Review D, 10.1103/PhysRevC.83.034002, 83, 3, 034002 [14 pages] , 2011.03.
8. Koji Harada, Hirofumi Kubo, and Yuki Yamamoto, Apparently noninvariant terms of U(N)xU(N) nonlinear sigma model in the one-loop approximation, Progress of Theoretical Physics, 123, 3, 475 - 498, 2010.03.
9. Koji Harada, Atsushi Ninomiya, and Hirofumi Kubo, More about the Wilsonian analysis on the pionless NEFT, Intern. J. Mod. Phys., 24, 16 & 17, 3191 - 3225, 2009.08.
10. Koji Harada, Nozomu Hattori, Hirofumi Kubo, and Yuki Yamamoto, Apparently noninvariant terms of nonlinear sigma models in lattice perturbation theory, Physical Review D, Vol.79, No.6, 065037, 2009.03.
11. Koji Harada, Problems in the derivations of the renormalization group equation for the low momentum nucleon interactions, Progress in Theoretical Physics, Vol. 120, No. 4, 741, 2008.10.
12. Koji Harada, Power counting for nuclear effective field theory and Wilsonian renormalization group, Nuclear Physics A, 790 (2007) 418c-421c, 2007.06.
13. Koji Harada, Anomalous dimensions determine the power counting: Wilsonian RG analysis of nuclear EFT, Nuclear Physics B, B758 [FS] (2006) 304 -- 329, 2006.11.
14. Koji Harada, Kenzo Inoue, Hirofumi Kubo, Wilsonian RG and redundant operators in nonrelativistic effective field theory, Physics Lett. B, 636, 305 -- 309, 2006.05.
15. Koji Harada, Yohei Mitsunari, and Nao-aki Yamashita, Effective Theory Approach to the Skyrme Model and Application to Pentaquarks, Progress in Theoretical Physics, 10.1143/PTP.113.1315, 113, 6, 1315-1366, 113, No.6 1315 -- 1366, 2005.06.
16. Koji Harada, RPA for light-front Hamiltonian field theory, Physical Review D, 60, 6, 60 No.6 065005-1 -- 065005-6, 1999.09.
17. Matthias Burkardt and Koji Harada, Light-front description for the theta dependence of meson masses in the massive Schwinger model, Physical Review D, 10.1103/PhysRevD.57.R5950, 57, 10, R5950-R5954, 57 No.10 5950--5954, 1998.05.
18. Koji Harada, Thomas Heinzl, and Christian Stern, Variational mass perturbation theory for light-front bound-state equation, Physical Review D, 10.1103/PhysRevD.57.2460, 57, 4, 2460-2474, 57 No.4 2460--2474, 1998.02.
19. Koji Harada and Atsushi Okazaki, Perturbative Tamm-Dancoff Renormalization, Physical Review D, 10.1103/PhysRevD.55.6198, 55, 10, 6198-6208, 55 No.10 6198--6208, 1997.05.
20. Koji Harada, Atsushi Okazaki, and Masa-aki Taniguchi, Dynamics of the light-cone zero modes: Theta Vacuum of the massive Schwinger model, Physical Review D, 10.1103/PhysRevD.55.4910, 55, 8, 4910-4919, 55 No.8 4910--4919, 1997.04.
21. Koji Harada, Atsushi Okazaki, and Masa-aki Taniguchi, Mesons in the massive Schwinger model on the light-cone, Physical Review D, 10.1103/PhysRevD.54.7656, 54, 12, 7656-7663, 54 No.12 7656--7663, 1996.12.
22. Koji Harada, Atsushi Okazaki, and Masa-aki Taniguchi, Six-body light-front Tamm-Dancoff approximation and wave functions for the massive Schwinger model, Physical Review D, 52 No.4 2429--2438, 1995.08.
23. Koji Harada, Takanori Sugihara, Masa-aki Taniguchi, and Masanobu Yahiro, Massive Schwinger model with SU(2)_f on the light cone, Physical Review D, 10.1103/PhysRevD.49.4226, 49, 8, 4226-4245, 49 No.8 4226--4245, 1994.04.
24. E. Abdalla, M. C. B. Abdalla, D. Dalmazi and Koji Harada, Correlation functions in non-critical (super-)string theory, International Journal of Modern Physics A, 7 No.29 7339--7363, 1992.01.
25. E. Abdalla, M. C. B. Abdalla, D. Dalmazi and Koji Harada, Correlation functions in super Liouville theory, Physical Review Letters, 68 No.11 1641--1644, 1992.03.
26. Koji Harada, Equivalence between the Wess-Zumino-Witten model and two chiral bosons, International Journal of Modern Physics A, 6 No.19 3399--3418, 1991.01.
27. Koji Harada, Fermion operator solution of the minimal chiral Schwinger model, Physical Review D, 42 No.12 4170--4181, 1990.12.
28. Koji Harada, Non-Abelian anomalous gauge theories in two dimensions and chiral bosonization, International Journal of Modern Physics A, 5 No.23 4469--4476, 1990.01.
29. Koji Harada, Hisamitsu Mukaida, Gauge invariance and systems with second-class constraints, Zeitschrift fuer Physik C -- Particles and Fields, 48 No.1 151--158, 1990.01.
30. Koji Harada, Comment on ``Quantization of self-dual field revisited'', Physical Review Letters, 65 No.3 267, 1990.07.
31. Koji Harada, Klaus D. Rothe, On a one-parameter family of equivalent bosonic actions for chiral QCD_2, Physics Letters B, 237 No.3,4 495--499, 1990.03.
32. Koji Harada, Currents in anomalous gauge theories, Nuclear Physics B, 329 No.3 723--738, 1990.01.
33. Koji Harada, Chiral Schwinger model in terms of chiral bosonization, Physical Review Letters, 64 No.2 139--141, 1990.01.
34. Koji Harada, Izumi Tsutsui, A modified Gauss Law operator in two dimensional anomalous gauge theories, Zeitschrift fuer Physik C -- Particles and Fields, 41 No.1 65--71, 1988.01.
35. Koji Harada, Izumi Tsutsui, Operator solutions of the bosonized chiral Schwinger model, Zeitschrift fuer Physik C -- Particles and Fields, 39 No.1 137--141, 1988.01.
36. Koji Harada, Izumi Tsutsui, Revealing the gauge freedom in the path-integral formalism, Progress in Theoretical Physics, 78 No.4 878--885, 1987.10.
37. Koji Harada, Izumi Tsutsui, A consistent Gauss Law in anomalous gauge theories, Progress in Theoretical Physics, 78 No.4 878--885, 1987.09.
38. Koji Harada, Izumi Tsutsui, On the path-integral quantization of anomalous gauge theories, Physics Letters B, 183 No. 3,4 311--314, 1987.01.
39. Koji Harada, Hiroshi Kubota, Izumi Tusutsui, Mass generation of the chiral Schwinger model, Physics Letters B, 173 No.1 77--80, 1986.05.