May 22, 2025
The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI)
The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI) Professor Hitoshi Murayama has been named one of the recipients of this year’s Particle Physics Medal of Japan Particle and Nuclear Theory Forum.
Murayama is receiving the medal for his contribution to the “Unified Description of the Nambu-Goldstone Theorem,” which was the subject of a paper published in Physical Review Letters in 2012, written by Murayama and then-graduate student Haruki Watanabe (currently Associate Professor at the University of Tokyo Department of Applied Physics), titled, “Unified Description of Nambu–Goldstone Bosons without Lorentz Invariance.” Kyoto University Yukawa Institute for Theoretical Physics Professor Yoshimasa Hidaka is also receiving the medal alongside Murayama and Watanabe for his 2013 Physical Review Letters paper, “Counting Rule for Nambu-Goldstone Modes in Nonrelativistic Systems”, which came to the same conclusion as Murayama and Watanabe, but using a different method.
“To explain all kinds of natural phenomena with one unified theory is the goal of physics. The science that is being recognized this year can be applied to a whole range of things from fridge magnets to supercooled atomic systems to the interior of neutron stars. We were able to come up with this idea thanks to Haruki Watanabe’s extensive knowledge on condensed matter physics, which combined very well with my expertise in field theory and modern geometry. This was not just a collaboration between two physicists from different fields. The discovery would not have materialized without interaction with mathematicians who actively work on symplectic geometry and representation theory at Kavli IPMU and UC Berkeley. I have since been able to continue to advance generalizations to cases involving spacetime symmetries. This chapter of research has been a highlight of my career and I am very grateful to receive this award,” said Murayama.
Murayama is being recognized for his work on explaining symmetry and its spontaneous breaking, which are important concepts in various fields of physics. "In relativistic field theory, spontaneous breaking of continuous symmetry causes Nambu-Goldstone bosons to appear, and their number is exactly the number of broken symmetries. This is the Nambu-Goldstone theorem. However, spontaneous symmetry breaking is also widely observed in non-relativistic systems without Lorentz invariance. In these systems, the properties of the Nambu-Goldstone bosons differ from system to system and had become a focus for research. In recent years, there have been attempts to understand these phenomena in a unified manner. The independent studies by Watanabe and Murayama, and by Hidaka, have presented a general theory of Nambu-Goldstone bosons in systems lacking Lorentz invariance. Both studies led to the following conclusions. First, they classify symmetry generators into commutative and noncommutative pairs based on the vacuum expectation value of the commutation relation of generators corresponding to the broken symmetry. Then, the number of Nambu-Goldstone bosons that appear is shown to be the sum of the number of commutative generator and the number of noncommutative pairs. In addition, both papers showed that the mode corresponding to the commutative generators has a linearly dispersion relation, while the mode corresponding to the noncommutative pairs has a quadratic dispersion relation. Their results used different methods, mainly the effective Lagrangian method in quantum field theory by Watanabe and Murayama and the Mori projection operator method by Hidaka. Their research, which contributed to the universal description of the Nambu-Goldstone theorem through these different theoretical approaches, is highly commendable and deserving of the Particle Medal," the committee said.
The Nambu-Goldstone theorem is one of the most important achievements by Yoichiro Nambu, who was awarded the 2008 Nobel Prize in Physics. It is a theorem on spontaneous symmetry breaking stating that when a continuous symmetry is spontaneously broken, a Nambu-Goldstone boson appears for every broken symmetry. However, the theorem assumes elementary particles are in a vacuum at an absolute temperature of zero degrees Celsius, and it cannot be applied to states with temperature and density. This has been a challenge for researchers until Murayama, Watanabe, and Hidaka made it possible to extend the Nambu-Goldstone theorem to states with temperature and density, paving the way for a unified treatment of the theorem in a variety of physical states.
The Particle Physics Medals has been awarded annually since 2000, and was established to further inspire research in particle physics, nuclear physics and related fields. Members of the Japan Physical Society’s Particle Theory Committee select the recipients. The researchers they choose are ones who have made significant contributions to particle theory and its surrounded fields. By recognizing the efforts by these researchers, the society aims to encourage the next generation of researchers to pursue their own original research.
Past recipients include the late Jiro Maki, who theorized that neutrinos could oscillate, and the late Toichiro Kinoshita, who was a world leader in quantum electrodynamics calculations. Kavli IPMU researchers who have received the medal include Visiting Senior Scientist Tsutomu Yanagida in 2020, and Professor Shigeki Matsumoto in 2024.
An award ceremony will be held during the 80th Annual Meeting of the Japan Physical Society, hosted at Hiroshima University between September 16 – 19.
About Hitoshi Murayama
Education and Experience
1991 PhD in Theoretical Physics, The University of Tokyo
1991 Research Associate, Tohoku University
1993 Postdoctoral Fellow, Lawrence Berkeley National Laboratory
1995 Assistant Professor of Physics, University of California, Berkeley
1998 Associate Professor of Physics, University of California, Berkeley
2000 Professor of Physics, University of California, Berkeley
2004 MacAdams Professor of Physics, University of California, Berkeley
2007 - 2018 Founding Director, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo
2008 Project Professor, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo
2018 Professor, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo
2019 University Professor, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, and Hamamatsu Professor
Awards
2002 Nishinomiya Yukawa Commemoration Prize in Theoretical Physics
2003 Fellow of American Physical Society
2011 Japanese Paperback Grand Prize, “What is the Universe made of?”
2011 Associate member, Japan Science Council
2013 Member of American Academy of Arts and Sciences
2016 Breakthrough Prize in Fundamental Physics (as a KamLAND member)
2017 100 influencers in the world, Einstein Legacy Project
2017 Humboldt Research Award
2017 Science Program Prize, Kenjiro Takayanagi Foundation, “Hitoshi Murayama's Great Adventure in Space”
2022 Fellow, American Association for the Advancement of Science
2024 Miller Senior Fellowship 2024
Related links
List of Particle Physics Medal recipients (in Japanese)
Related articles
Theorem unifies superfluids and other weird materials (June 8, 2012)
Kavli IPMU’s Tsutomu Yanagida Awarded 20th Particle Physics Medal of Japan (November 17, 2020)
Shigeki Matsumoto awarded the 2024 Particle Physics Medal (October 11, 2024)
