A new framework of loop quantization that assimilates conformal and scale invariance is constructed and is found to be applicable to a large class of physically important theories of gravity and gravity-matter systems. They include general relativity and scale-invariant scalar-tensor and dilaton theories. Consequently, matter to be coupled to such theories is restricted to be conformal or scale invariant. Standard model-type systems naturally fall into this category. The new loop quantization follows from a novel conformally generalized Holst action principle. In contrast to standard loop quantum gravity, the resulting quantum geometry is not beset by the Immirzi ambiguity and has no definitive area gaps within the considered large class of theories of gravitation. As an additional feature, the scale invariance gives rise to a conservedWeyl current and we discuss briefly its possible implication on the problem of time in quantum gravity.
Wang, C. H-T., & De P. F. Rodrigues, D. (2018). Closing the gaps in quantum space and time: Conformally augmented gauge structure of gravitation. Physical Review D, 98(12), . https://doi.org/10.1103/PhysRevD.98.124041