Bekenstein Bound for Approximately Local Charged States

Abstract

We generalize the energy-entropy ratio inequality in quantum field theory (QFT) established by one of us from localized states to a larger class of states. The states considered in this paper can be in a charged (non-vacuum) representation of the QFT or may be only approximately localized in the region under consideration. Our inequality is $S(\Psi |\!| \Omega) \le 2\pi R \, ( \Psi, H_\rho \Psi ) + \log d(\rho) + \varepsilon$, where $S$ is the relative entropy, where $R$ is a "radius" (width) characterizing the size of the region, $d(\rho)$ is the statistical (quantum) dimension of the given charged sector $\rho$ hosting the quantum state $\Psi$, $\Omega$ is the vacuum state, $H_\rho$ is the Hamiltonian in the charged sector, and $\varepsilon$ is a tolerance measuring the deviation of $\Psi$ from the vacuum according to observers in the causal complement of the region.