# 16th-DEX Workshop - Dark Energy as a Vector Field

### Abstract

The $$\Lambda$$ Cold Dark Matter model ($$\Lambda$$CDM) represents the current standard model in cosmology. Within this, there is a growing tension between the values of the Hubble constant, $$H_0$$, inferred from local distance indicators and the angular scale of fluctuations in the Cosmic Microwave Background (CMB). In this talk I will describe a model of the late-time cosmic acceleration derived from a generalised Proca action, where a cosmic vector field causes modifications to gravity. The model features a different expansion history from $$\Lambda$$CDM which approaches a de Sitter attractor solution at late times, and accomodates an evolution in $$H_0$$ that allows us to reduce the tension in $$H_0$$. The additional vector degree of freedom can lead to better compatibility with datasets of SN Ia, CMB, BAOs, and RSDs in comparison to the $$\Lambda$$CDM model. This property presists even with the integrated-Sachs-Wolf (ISW) effect, a test that the cubic scalar Galileon fails.