title: Quantum entropy and special relativity.
abstract: We consider a single free spin- 1 / 2 particle. The reduced density matrix for its spin is not covariant under Lorentz transformations. The spin entropy is not a relativistic scalar and has no invariant meaning.
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: Asher
authors.initials: A
authors.lastname: Peres
authors.forename: Petra F
authors.initials: PF
authors.lastname: Scudo
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Terno