Recent progress in particle physics has revealed that there may be an untimate theory called the `M' theory, and it predicts that our universe is a spatially 3-dimensional brane (surface) embedded in a higher dimensional spacetime. The present project is intended to develop a new cosmology based on the brane-world scenario.
Through this project, we have succeeded in obtaining several important results, including a systematic formulation of effective gravity on the brane, a new viable model of inflation, clarification of possible roles of a hidden brane, classical and quantum stabilities/instabilities of the brane-world, and basic properties of gravity on the brane. These achievements strongly suggest that the brane-world scenario can open up a new paradigm in cosmology. However, at the same time, we have become aware that we are still far from a complete understanding of observational/experimental implications of the brane-world. We therefore consider that the importance of research in the brane-world cosmology has increased more than ever before.