Casimir force on a piston at finite temperature in Randall-Sundrum models

The Casimir effect for a three-parallel-plate system at finite temperature within the framework of five-dimensional Randall-Sundrum models is studied. In the case of the Randall-Sundrum model involving two branes we find that the Casimir force depends on the plate distance and temperature after one outer plate has been moved to a distant place. Further we discover that the sign of the reduced force is negative if the plate and piston are located close together, but the nature of reduced force becomes repulsive when the plate distance is not very small and finally the repulsive force vanishes with extremely large plate separation. A higher temperature causes a greater repulsive Casimir force. Within the framework of a one-brane scenario the reduced Casimir force between the piston and one plate remains attractive no matter how high the temperature is. It is interesting that a stronger thermal effect leads to a greater attractive Casimir force instead of changing the nature of the force.