I aim to reveal the whole cosmic history from the beginning to the present day or the future. People believe that in the early universe, the universe had experienced the accelerated expansion called inflation, and the present universe is also accelerated by dark energy. We must make these phenomena clear. With this in mind, I investigated the models which unify the inflation and late-time acceleration. Now, I’m interested in the details of the gravitational wave created during inflation and the effect of the vacuum expectation value of the Higgs particle on the evolution of the universe.