Speaker
Description
The significant tensions in constraints on the Hubble constant ($𝐻_0$) and clustering amplitude ( $𝑆_8$) between early- and late-universe observations challenge key assumptions of the LCDM cosmological model. One of these assumptions is the presence of cold dark matter, a yet-to-be-detected non-relativistic particle with minimal interaction with the Standard Model that dominates the mass budget of the universe.
We propose a phenomenological model where dark matter’s pressure-to-energy ratio, or equation of state, w, evolves over time, enabling it to influence both the universe’s expansion rate $𝐻_0$ and structure formation $𝑆_8$. The model reduces the $𝐻_0$ tension from ∼5𝜎 to ∼3𝜎 and the 𝑆8 tension from ∼3𝜎 to ∼1𝜎.
Moreover, this model explains the anomalously large Integrated Sachs-Wolfe (ISW) effect observed in cosmic voids, a key puzzle in large-scale structure analyses. Observations suggest an unexpectedly strong ISW signal from voids, which our model enhances by a factor of ~2. This provides a testable prediction and supports the idea that dark matter properties influence both small- and large-scale cosmology.
These results extend to unified or interacting dark matter-energy models, with void ISW signals offering a promising avenue for resolving cosmological tensions.
