Conformal structure of FLRW cosmology: spinorial representation and the $$ \mathfrak{so} $$ (2, 3) algebra of observables

Abstract

Abstract It was recently shown that the homogeneous and isotropic cosmology of a massless scalar field coupled to general relativity exhibits a new hidden conformal invariance under Mobius transformation of the proper time, additionally to the invariance under time-reparamterization. The resulting Noether charges form a $$ \mathfrak{sl}\left(2,\mathbb{R}\right) $$ sl 2 ℝ Lie algebra, which encapsulates the whole kinematics and dynamics of the geometry. This allows to map FLRW cosmology onto conformal mechanics and formulate quantum cosmology in CFT1 terms. Here, we show that this conformal structure is embedded in a larger $$ \mathfrak{so} $$ so (3, 2) algebra of observables, which allows to present all the Dirac observables for the whole gravity plus matter sectors in a unified picture. Not only this allows one to quantize the system and its whole algebra of observables as a single irreducible representation of $$ \mathfrak{so} $$ so (3, 2), but this also gives access to a scalar field operator $$ \hat{\phi} $$ ϕ ̂ opening the door to the inclusion of non-trivial potentials for the scalar field. As such, this extended conformal structure might allow to perform a group quantization of inflationary cosmological backgrounds.