Department of Physics, Faculty of Science and Technology, Keio University
Constructing New Transport Theory Based on Nature of Neutrinos to Explain Supernova Explosions
The Yamamoto Laboratory in the Department of Physics, Faculty of Science and Technology, Keio University is conducting theoretical research on particle and nuclear physics including topics such as quarks and neutrinos, and on astrophysics including the early universe and supernova explosions.
In modern physics, elementary particles called quarks and neutrinos are the smallest building blocks that constitute matter. But even today there are many questions regarding the nature of these particles.
“The theory behind how microscopic elementary particles—such as quarks, neutrinos, and electrons—behave is already established. Their dynamics can be described by the standard theory of particle physics. However, understanding of how matter is made up of a collection of these particles, or of the nature of this matter, is a generally non-trivial, difficult question.”
“So at our research lab we have constructed a kinetic theory to describe the time evolution of a collection of elementary particles. Based on this kinetic theory, we primarily conduct research on predicting new physical phenomena, as well as on understanding the origins of supernova explosions.”
In the phenomenon known as a supernova explosion that occurs when a large mass star reaches the end of its life, it is known that most of the gravitational energy released when the star undergoes gravitational contraction is transported outward by neutrinos.
“Efficient outward transport of energy by neutrinos plays an extremely important role in determining whether a supernova explosion will occur. However, the problem has been that by using the conventional kinetic theory describing transport of neutrino energy and momentum, for some reason it has not been possible to theoretically reproduce a supernova explosion. This has been an unsolved problem in astrophysics. In fact, there is a big flaw in this neutrino transport theory, which is that neutrinos have the extremely mysterious property of violating left-right symmetry. For some reason, until now only left-handed neutrinos have been discovered, and no right-handed neutrinos have been discovered.”
“Neutrinos have this mysterious property known as chirality, which violates left-right symmetry, and this key nature of elementary particles, neutrinos, has been completely ignored in transport theory to date. We have constructed a theory that overcomes this for the first time, and right now our direction is to use this theory to cause a supernova explosion.”
The Yamamoto Laboratory is striving to understand the origins of supernova explosions through an understanding of the nature of neutrinos.
In addition, under the theme of researching the nature of matter under extreme conditions, the lab is also studying the extremely hot states of matter that existed immediately after the Big Bang, as well as the extremely dense states of matter inside neutron stars.