Search for possible signals of space-time non-commutativity from ACT DR6

Abstract

The non-commutative geometry offers an effective framework for describing physics at the Planck scale, incorporating generic quantum-gravitational effects through an intrinsic minimal length and the $\kappa$-deformed space-time stands out as a particularly well-developed model based on a Lie-algebraic type non-commutative space-time structure. We investigate the inflationary paradigm and the associated primordial perturbations within the framework of $\kappa$-deformed non-commutative space-time. By constructing a scalar field theory invariant under the $\kappa$-Poincar\'e algebra, we derive the deformed oscillator algebra for the field modes of the primordial perturbations resulting in the non-trivial scale dependent modification of both the scalar and tensor power spectra. Further, we compute the corresponding $\kappa$-deformed corrections to the scalar spectral index and its running, finding that the $\kappa$-deformation naturally provides a higher value for spectral index which offers a potential resolution to the discrepancy between the values reported by PLANCK and ACT. Finally we perform a comprehensive Bayesian analysis using the latest ACT DR6 data, constraining the $\kappa$-deformed non-commutative length scale to $\lambda=2.17^{+2.33}_{-1.53}\times 10^{-30}m$ at the $1\sigma$ confidence level, suggesting the precision cosmology as a powerful probe of quantum gravity phenomenology.