Abstract: |
We study the entanglement entropy of excited states in two dimensional conformal field theories (CFTs). Especially we consider excited states obtained by acting with primary operators on a vacuum. We show that under its time evolution, entanglement entropy increases by a finite constant when a causality condition is satisfied. Moreover, in rational CFTs, we prove that this increased amount of (both Renyi and von-Neumann) entanglement entropy always coincides with the log of quantum dimension of the primary operator. |