Imagine to submerge a pendulum in a supefluid. Of course we assume an ideal pendulum, whose joint does not freeze or deteriorate due to the extremely low temperature. We also assume the superfluid to be at zero temperature, so we can neglect its normal component.
What happens to its oscillations? Are they somehow damped? Or do they keep a constant amplitude?
In other words: can some energy be transferred from the pendulum to the superfluid (for example, thanks to the excitation of sound waves in the superfluid)?