Running cosmological constant in light of recent CMB-BAO data

Abstract

We revisit single-field slow-roll inflation driven by a running cosmological constant, i.e. a cosmological constant receiving a logarithmic radiative correction, in light of the latest CMB-BAO data. The relative radiative correction $δ$ is treated as a free parameter of the model and allowed to be positive or negative. For positive $δ$, the predictions interpolate between a logarithmic regime and a linear inflation one. Compatibility with CMB-only data is confined to a narrow stripe near the $2σ$ border where $δ$ is relatively large. On the other hand, the predictions fit easily within the constraints including BAO data in a wide range of parameters. For negative $δ$, the slow-roll approximation breaks down at small field values and the predictions are excluded by data. However, once the effective mass contribution inside the logarithmic correction is taken into account, the negative $δ$ potential develops a local maximum and behaves like a hilltop model, achieving compatibility with CMB-only data, while agreement with CMB-BAO data is possible only at $2σ$.