Aiming for the Ultimate Elementary Particle Theory
Hisao Suzuki , Professor
Faculty of Science/ Graduate School of Science (School of Science / Department of Physics)
High school : Shizuoka Prefectural Iwata Minami High School
Academic background : Doctorate at Nagoya University
- Research areas
- Elementary particle theory
- Research keywords
- elementary particles, superstring theory, quantum theory, dark matter, dark energy
What are you aiming to achieve?
My research is into elementary particles, which are the smallest particles it is possible to obtain. Professors Kobayashi and Masukawa were awarded the Nobel Prize recently, and so most people have at least heard the term. The closest elementary particles to us are electrons, for example, which form the basis of electrical currents. Electrons and other particles that carry an electrical charge attract and repel one another using electric force. They also have gravity. These electrical and gravitational forces are believed to be caused by particles such as photons and gravitons. In my research, I am aiming for a unified theory of particles, which mediates the elementary particles and forces that configure these substances. At present, superstring theory is considered to be a strong candidate for this.
What is superstring theory?
Superstring theory makes the argument that what we always thought were particles up until now may in fact be made of strings.
What is good about superstring theory?
For example, many of you will know about something known as polarization of light. Polarization occurs because the electrical field in light vibrates and creates waves. At the same time, at the micro level, quantum theory is the controlling theory, where light also acts as particles. It’s difficult, however, to imagine how it can be a particle but also a wave. Let’s try to explain it from the perspective of string theory. As shown in the diagram, in string theory, photons are believed to be positive and negative electric charges at each end of a string. An electric field occurs from the positive charge in the direction of the negative charge. This field proceeds forward while vibrating, so the direction of the electric field changes while it is being propagated. Do you see? It’s easier to understand particles with an electric field this way, isn’t it? You don’t think so? Oh dear… I’ll have to try again. (Takes a breath). In any case, string theory is in fact not simply there to make the nature of particles easier to understand. Rather, superstring theory is the only theory currently around that can explain gravity in a way that integrates it with quantum theory. What do you think of, by the way, when someone says “gravity”?
Well, I learned about Newton’s gravitational law…
Science is a dramatic adventure that continues today. In fact, Newton’s gravitational law, which you learn in high school, is not a true theory. According to Newton’s gravitational law, for example, the strength of the force depends upon the distance between the two objects and their mass, so if you change the distance and the mass, the impact will be communicated immediately on the other object. According to Einstein’s theory of relativity, however, light and matter cannot travel faster than the speed of light. And Einstein’s general theory of relativity is a fusion of gravitational theory and relativity theory.
The “general theory of relativity” sounds extremely difficult…
The general theory of relativity is a theory that has been around for about 100 years now, since before we were born. Our ways of teaching have also evolved, so nowadays it’s not that difficult a theory to understand, and if you come to study in the Physics department you will experience its beauty. At HokkaidoUniversity, we give lectures to first year students on the special theory of relativity. The truths of nature are also works of art obtained by the creativity of man.
And was there a connection between gravitational theory and superstring theory?
The study of electromagnetism includes a micro theory known as quantum electrodynamics. According to this, photons generate electrical force and magnetic force. At the same time, the general theory of relativity has no micro theories created in regard to it. We can’t say in detail, but if you apply the general theory of relativity to quantum theory, there are some difficulties, and so quantum theory for gravity is still not understood. This is a big problem.
And this is where superstring theory comes in?
Yes, that’s right. Superstring theory is a separate theory to the general theory of relativity in the micro world, but in the macro world it is the equivalent of the general theory of relativity. It has integrity as quantum theory, and furthermore, the timbre of the vibration of various strings is compatible with the various elementary particles, while electrons and photons are also one of these timbres. In this way, superstring theory is not simply a micro-successor to the general theory of relativity; it is expected to be a major unifying theory, unifying matter and force. We expect superstring theory to also explain the history of space.
I thought that elementary particle theory had already been completed …?
No, in fact, the opposite is true. At the moment, the more researchers learn about space, the more we realize we don’t really know anything. Look at the diagram to the left. It has been observed that we only actually understand 5% of the matter that makes up space. 25% of the total is unknown matter known as dark matter. This doesn’t mean it is not giving off light, but rather that it is made up of matter other than the elementary particles we know about. There is also the completely unknown dark energy, which exists throughout space. It is all around us and we don’t even know what it is. We hope that superstring theory will predict what these things are. You might even be the person who discovers the identity of dark matter!