We study the causal structure of the minimal surface of the four-gluon
scattering, and find a world-sheet wormhole parametrized by Mandelstam
variables, thereby demonstrate the EPR = ER relation for gluon scattering. We
also propose that scattering amplitude is the change of the entanglement
entropy by generalizing the holographic entanglement entropy of Ryu-Takayanagi
to the case where two regions are divided in space-time.Comment: 6 pages, 6 figures; v2: major revision, comments added in Section V,
refs added, version for publicatio