# Agenda

# Wednesday 12 September 2018

### Quantum proper time

#### Fabio Costa

The proper time of a relativistic particle depends on its trajectory: acceleration, or gravitational fields, can cause trajectories with equal starting and final points to accumulate different proper time. What happens to a particle that is in a quantum superposition of different trajectories? How does the particle decide how much proper time it should experience? I will show how such questions lead to the prediction of novel effects at the interface of quantum theory and relativity, in a low-energy regime insensitive to quantum field effects. I will further introduce an effective formalism for composite relativistic quantum particles, which can act as “clocks” measuring quantum proper time. I will finally propose that the formalism can facilitate the analysis of unexplored physical regimes, where quantum properties of gravity can lead to quantum causal structures.