Abstract
We present a formulation of the single-trajectory entropy using the trajectories ensemble.The single-trajectory en-tropy is affected by its surrounding trajectories via the distribution function.The single-trajectory entropies are studied in two typical potentials,i.e.,harmonic potential and double-well potential,and in viscous environment by interacting tra-jectory method.The results of the trajectory methods are in agreement well with the numerical methods(Monte Carlo simulation and difference equation).The single-trajectory entropies increasing(decreasing)could be caused by absorption(emission)heat from(to)the thermal environment.Also,some interesting trajectories,which correspond to the rare evens in the processes,are demonstrated.