The search for a consistent theory of finite-range gravity is a longstanding problem and well motivated by both theoretical and observational considerations. On the theoretical side, whether there exists such a consistent extension of general relativity by a mass term is a basic question of classical field theory. After Fierz and Pauli's pioneering attempt in 1939, this issue has been attracting a great deal of interest. On the observational side, continuing experimental probes of gravity have revealed new unexpected phenomena at large scales. One of the most profound discovery is the cosmic acceleration. The extremely tiny energy-scale associated with the cosmic acceleration hints that gravity might need to be modified in the infrared. The massive gravity is one of the most interesting attempts in this direction. In this review, after reviewing the history and recent developments of massive gravity, I will describe cosmological solutions and their stability.

It is difficult to obtain sufficient sampling in the conformational space for biomolecules. This is because biomolecular systems usually have many free-energy local-minimum states, and in conventional canonical-ensemble simulations, the system gets trapped in such local-minimum states. To solve this problem, we recently proposed the replica-permutation method and the Hamiltonian replica-permutation method. Moreover, we applied the Hamiltonian replica-permutation method to fragments of amyloid-β peptides to investigate their dimerization process. The amyloid-β peptide tends to form amyloid fibrils, which are associated with the Alzheimer's disease. The dimerization process corresponds to the early stage of the amyloid fibril formation process. It is necessary to clarify the dimerization process in order to find a remedy for Alzheimer's disease.

By the recent astronomical and astrophysical observations, one fourth of the total energy of the universe was known to be in a form of the unknown particle, “dark matter”. Many experimental activities are on-going all over the world to reveal the nature of this mysterious particle. Direct detection experiments aim to detect the energy deposited to the detector on the earth by the elastic scattering of the dark matter and the ordinary matter. Among many direct detection experiments, the direction-sensitive method is said to provide a strong evidence of the dark matter due to the motion of the solar system in the galaxy. NEWAGE is one of the direction-sensitive dark matter search experiments and recently updated the world-best direction sensitive dark matter limits by the measurement in Kamioka underground laboratory.

Theoretical study on the initial dynamics of photoinduced nucleation is reviewed. Employing a model of localized electrons coupled with an optical phonon mode, we numerically calculated the dynamics of photoinduced nuclei. The multifractal analysis on the geometric patterns of their boundary is suitable for understanding the dynamics of adiabatic/non-adiabatic electronic transitions during the first picoseconds after photoexcitation. We revealed that the photoinduced nucleation starts with two different processes; formation of photoinduced nuclei by rearrangement of the Franck-Condon states and their growth with coalescence of each other. This two-stage dynamics of nucleation is characteristic of the initial processes of photoinduced cooperative phenomena.