Physics

The elementary particles that are considered to be the smallest units constituting matter are currently known to be quarks and leptons. In addition, other particles that are currently recognized as elementary particles include the gauge bosons and the Higgs particles. There are four kinds of gauge bosons: photons, weak bosons, gluons, and gravitons. They are considered quanta that mediate four basic interactions (electromagnetic interaction, weak interaction, strong interaction, and gravitational interaction) that work between elementary particles. The Higgs boson is believed to be the origin of particle mass. No theory has so far managed to unify all these elementary particles and their interactions. However, a unified description of the interactions between elementary particles other than gravity has been successfully described within the framework of “the Quantum Field Theory”. 

On the other hand, a theory that can describe gravitational interactions, “the General Relativity Theory” was proposed by Albert Einstein. It serves as a basic theory for the study of galaxies and celestial bodies in the universe. However, this theory is not a quantum theory. In order to describe gravitational interactions in a unified manner, a quantum theory that includes gravitational interactions is necessary. To this date, there is no complete quantum theory, and it is one of the unsolved problems in modern physics research. 

If a theory that can describe all elementary particles and the four basic interactions in a unified manner including quantum gravity is completed, it is expected to become a theory that can consistently explain everything from the ultra-micro world to the ultra-macro world. As the most promising candidate, “the Superstring Theory” has attracted attention and is being studied by many elementary particle theory researchers. 

In the Physics Laboratory, we research themes related to “the Quantum Field Theory”, “the General Relativity Theory”, and “the Superstring Theory”. A concept called the Holography Principle was proposed as one way of understanding these physical theories in a unified manner. Specific examples of this Holography Principle include the concepts called “Ads/CFT correspondence” and “gauge/gravity correspondence” in the Superstring Theory. Our Laboratory explores whether this concept can be extended to finite temperature systems. A key issue in this research is an effect called “Quantum Entanglement”. Entanglement entropy is known as a quantity that specifically describes this effect. Our Laboratory contributed to showing that the method of “thermo-field dynamics” is effective as a method of extending this quantity to the finite temperature system. Our laboratory is conducting research with the goal of obtaining a unified understanding of the finite temperature system by applying such a calculation method to the concept of the above-mentioned Holography Principle.