Unitarity and Information in Quantum Gravity: A Simple Example

In approaches to quantum gravity, where smooth spacetime is an emergent approximation of a discrete Planckian fundamental structure, any effective field theoretical description would miss part the degrees freedom and thus break unitarity. This applicable also trivial gravitational (low energy) idealizations realized by use Minkowski background geometry which, as with other geometry, corresponds, in description, infinitely many different closely degenerate microstates. The existence such microstates provides large reservoir q-bit for information be coded at end black hole evaporation opens way natural resolution puzzle. this paper we show that these expectations can made precise simple gravity model cosmology motivated loop gravity. Concretely, even when fundamentally unitary, microscopic irrelevant low-energy cosmological observers are suitably ignored, pure states evolve into mixed due decoherence structure. Moreover, relevant physical regime hidden do not carry “energy” realize, fully context, idea (emphasized before Unruh Wald) take place without dissipation, now concrete strongly All strengthens perspective quite conservative puzzle destroyed but simply degraded (made unavailable observers) correlations structure Planck scale.