What is the world made of? The goal of particle physics is to provide the answer to this profound question. For more than a century, physicists have advanced our understanding of the fundamental building blocks of matter. Neutrinos are among the most abundant and least understood of all elementary particles that make up the Universe, and are thought to hold the keys to unlocking the mysteries of the Universe.

The University of Tokyo has been leading the field of neutrino physics for decades. The Nobel Prize in Physics in 2002 and 2015 were respectively awarded to the discoveries made using Kamiokande and its successor, Super-Kamiokande, both of which are research facilities hosted by the University of Tokyo. The construction of the third generation facility, Hyper-Kamiokande, started in 2020.

In this lecture, I will talk about what we have learned from neutrinos and what we can expect in the future.

Mathematical modeling deals with various phenomena using mathematical equations. In the field of biology, it is very useful for understanding biological phenomena, from the behavior of molecules to the evolution of species. In this lecture, I would like to introduce the SIR (Susceptible Infected Recovered) model of infectious diseases, taking the case of a new type of coronavirus infection (COVID-19) as an example. In the SIR model, the populations of S, I, and R compartments are given as variables of time, and the changes in population size are described using the simultaneous ordinary differential equations.

I hope that, through this lecture, you will not only learn the basic theory of mathematical modeling of infectious disease dynamics, but also discover effective measures against COVID-19 by developing the model.