Topological dark energy from spacetime foam: A challenge for $Λ$CDM

Abstract: Using only the standard considerations of spacetime foam and the Euclidean Quantum Gravity techniques known long ago, we result to a model of Topological Dark Energy (TDE) that outperforms the standard $\Lambda$CDM paradigm with regard to data fitting efficiency. Specifically, it is known that at the foam level, topologically non-trivial solutions such as instantons appear. In the particular case of Einstein-Gauss-Bonnet gravity, we obtain an effective dynamical dark energy term proportional to the instanton density, and the latter can be easily calculated through standard techniques. Hence, we can immediately extract the differential equation that determines the evolution of the topologically induced effective dark energy density. Significantly, this TDE scenario allows for changing sign of dark energy during the cosmic evolution and also exhibits Dark Energy interaction with Dark Matter. We confront the TDE scenario, in both flat and non-flat cases, with Pantheon+/SH0ES Supernovae Type Ia (SNIa), Baryonic Accoustic Oscillations (BAO), and Cosmic Chronometers (CC) datasets. By applying standard model selection methods (AIC and DevIC information criteria), we find a moderate but statistically significant preference over $\Lambda$CDM scenario. Finally, we show that the TDE scenario passes constraints from Big Bang Nucleosynthesis (BBN) and thus does not spoil the thermal history of the Universe.