The cosmological constant problem and quantum spacetime reference frame

Abstract

We generalize the idea of quantum clock time to quantum spacetime reference frame via physical realization of a reference system by quantum rulers and clocks. Omitting the internal degrees of freedom (such as spins) of the physical rulers and clocks, only considering their metric properties, the spacetime reference frame is described by a bosonic nonlinear sigma model (NLSM). We study the quantum behavior of the system under approximations, and obtain (1) a cosmological constant valued [Formula: see text] ([Formula: see text] the critical density at near current epoch) which is very close to the observations; (2) an effective Einstein–Hilbert term; (3) the ratio of variance to mean-squared of spacetime interval tends to a universal constant [Formula: see text] in the infrared region. This effect is testable by observing a linear dependence between the inherent quantum variance and mean-squared of the redshifts from cosmic distant spectral lines. The proportionality is expected to be the observed percentage of the dark energy. The equivalence principle is also generalized to the quantum level.